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Reconditioning Detachable Bits by Mechanical Grinding, Hot Milling, and Hand Grinding

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RECONDITIONING DETACHABLE BITS BY
MECHANICAL GRINDING, HOT MILLING,
AMD HAND GRINDING
and
A STUDY OF ROCK DRILL
LUBRICANTS
A Thesis
Presented to
The Department of Mining Engineering
Montana School of Mines
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Mining Engineering
/4S3/
by
Don Edwin Harvey
May 20, 1941
MONTANA SUhu'oL •
, ~„ .....iiuaVi
fKBRARY; MONTANA TECH
X a u m , MONTANA
UMI Number: EP33267
All rights reserved
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a note will indicate the deletion.
UMT
Dissertation Publishing
UMI EP33267
Copyright 2012 by ProQuest LLC.
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unauthorized copying under Title 17, United States Code.
ProQuest*
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TABLE OF CONTENTS
CHAPTER
PAGE
1
ACKNOWLEDGEMENT
1
11
THE PROBLEM AND ITS IMPORTANCE
2
Statement of problem
2
Importance of the study
2
SECTION 1
CHAPTER
PAGE
111
5
BIT MANUFACTURING
Steel for "bit manufacture
5
Forging furnace
5
Heating of steel
5
Forging operation
6
Pressing operation
7
Annealing
8
Machine shop work
8
SECTION 11
CHAPTER
PAGE
IV
13
V
x
BIT RECONDITIONING
General considerations and definations of terms used
13
Drilling action
13
General sharpening practice
14
MECHANICAL GRINDING
16
Bit sorting
17
Description of grinding unit
18
PAGE
CHAPTER
VI
VII
Bit holders
19
Facing operation
20
Edging or gauging operation
21
HARDENING AND TEMPERING
23
Furnaces
23
Quenching tray
24
Method of hardening and tempering
26
BIT TESTING
29
System followed
29
Marking of bits
29
Measuring bits
30
VIII
BIT RECONDITIONING
38
IX
HOT MILLING
45
X
XI
General mechanics of the process
46
Development trends
46
Receeding cut
48
Approaching cut
48
Gauging operation with single cutter
50
Double cutter
52
HOT MILLING AT A STANDARD PLANT
53
Bit sorting
55
Heating
55
Milling
55
Gauging operation
56
BIT TESTING
58
CHAPTER
PAGE
XII
BIT RECONDITIONING BY HOT KILLING
64
XIII
HAND GRINDING
70
XIV
BIT TESTING
72
XV
SHARPENING BY HAND GRINDING
76
XVI
CONCLUSION
81
SECTION 111
CHAPTER
PAGE
I
A COMPARISON OF ROCK DRILL LUBRICATION OILS
88
II
UNDERGROUND TESTING FOR CHARACTER OF OIL MIST AND
LUBRICATION OF MACHINE
95
General set-up
95
III
OIL TEST T/VITE DRIFTER
97
IV
LUBRICATION DATA DRIFTER
100
V
OIL TEST 7a TH STOPER
101
VI
LUBRICATION DATA STOPER
104
VII
SUMMARY AND CONCLUSIONS
105
BIBLIOGRAPHY
109
LIST OF FIGURES
FIGURE
PAGE
FORGING FURNACE
6
AJAX FORGER
6
BLISS PRESS
7a
STEPS IN BIT FORGING AND PRESSING
7a
ANNEALING FURNACE
9
MILLING MACHINE
9
MILLING MACHINE ( D r i l l s )
9
MILLING MACHINE ( M o t o r s )
9
DETACHABLE BIT
12
MECHANICAL GRINDING ROOM
16
MECHANICAL GRINDING UNITS
17
SORTING CHANNEL
18
HARDENING UNIT
24
INTERIOR OF FURNACE
24
FLOWSHEET OF PROCESS
27
RECEEDING AND APPROACHING CUTS
47
GROWTH OF FLASH
49
SINGLE AMD DOUBLE CUTTERS
51
HOT MILLING UNIT
54
HAND GRINDER
71
SUMMARY
87
PLAN OF 3405-XCN
95
LIST OF TABLES
TABLE
PAGE
COMPOSITION OF BIT STEEL
5
MECHANICALLY GROUND BITS
Test #1
31
Test #2
32
Test #3
33
Test #4
34
Test #5
35
Test #6
36
Test #7
37
Grind #1
39
Grind #2
40
Grind #3
41
Grind #4
42
Grind #5
43
Grind #6
44
HOT MILLED BITS
Test #1
59
Test #2
60
Test #3
61
Test #4
62
Test $6
63
Hot mill #1
65
Hot mill #2
66
Hot mill #3
67
Hot mill #4
68
TABLE
PAGE
Hot mill #5
69
HAND GRINDING
Test #1
73
Test #2
74
Test #3
75
Grind #1
78
Grind #2
79
Grind #3
8Q
CONCLUSION
Mechanical grinding
84
Hot milling
85
Hand grinding
86
SECTION 111
OIL FILM
Oil #1
90
Oil #2
90
Oil #3
90
Oil #4
90
Oil #5
91
Oil #6
91
Oil #7
91
Oil #8
91
AMOUNT OF RUST
Oil #1
92
Oil #2
92
AMOUNT OF RUST
PAGE
Oil #3
92
Oil #4
92
Oil #5
93
Oil #6
93
Oil #7
93
Oil #8
93
OIL TEST WITH DRIFTER
Test #1
97
Test #2
97
Test #3
97
Test #4
98
Test #5
*
98
Test #6
98
Test #7
99
Test #8
99
LUBRICATION DATS DRIFTER
100
OIL TEST WITH STOPER
Test jf9
101
Test #10
101
Test #11
101
Test #12
102
Test #13
102
Test #14
102
OIL TEST WITH STOPER
PAGE
Test #15
103
Test #16
103
LUBRICATION DATA STOPER
104
SUMMARY AND CONCLUSIONS
105
CHAPTER 1
INTRODUCTION AND ACKNOWLEDGEMENTS
This report is based upon work carried out during the academic
year of 1940-1941. The study was pursued under the joint supervision
of the Engineering Research Department of the Anaconda Copper Mining
Co., and the Department of Mining of the Montana School of Mines.
The work was carried out at the Hawkesworth Drill Shop and two
small custom bit sharpening plants located in Butte, Montana. Underground testing was done at the Leonard mine.
At this point the writer wishes to express his gratitude to the
following men for guidance and assistance. Messers E. R. Borcherdt
and J. A. O'Neill of the Research Department, Professor A. E. Adami
of the Montana School of Mines, J. S. Mhyre, foreman of the Hawkesworth Plant, Hale Strock, foreman of the Leonard mine. I also wish
to express my appreciation to those other members of the Research
Dept. and the Operating Dept. of the A. C. M. for much valuable
assistance.
CHAPTER 11
THE PROBLEM AND ITS IMPORTANCE
Statement of the problem. There are three major sections to
this report. These are (l) the manufacture of detachable bits; (2) a
discussion of mechanical grinding, hot milling, and hand grinding as
methods of sharpening detachable bits; and (3) a study of eight different rock drill oils.
Importance of the study. In order to realize the importance
of the part played by detachable bits in mining it is necessary to
review the salient facts.
Mining is divided into three major operations (1) breaking of
the ore or waste; (2) mucking or loading the broken rock for transportation; and (3) timbering. These three operations are closely
associated and any inovation which makes either one more efficient
will improve the general efficiency of the mine.
The adoption of detachable bits was a step in the right direction.
The basic principle of the detachable bit is the construction
of a drill steel shank and a bit, each a separate part. This permits
(l) the bit to be made of a steel which can be hardened to a high
degree; (2) the shank or rod to which the bit is attached to be made
of a different steel selected for toughness and resistance to fatigue;
and (3) the bit because of its small weight and bulk to be conveniently transported between drill shop and working face.
3
The tangible factors which affect the cost per foot drilled
are enumerated:
1. Cost of transporting drill steel and bits from shop to
working place and return.
2.
Shop operating expense for reconditioning drill steel
and bits.
3. Cutting speed or rate of penetration.
4. Number of feet drilled per bit dulled,
5.
Feet drilled per machine shift.
6.
Loss of drill steel from all causes.
7.
Drill machine repair.
8. Hazards in transporting and use of steel and bits.
9.
Capital expense.
An inspection of the above list reveals that items 1, 2, 6,
and 8 are those concerned with the form of the drill steel, whether
of the conventional type or detachable bit type, and it is readily
seen that the adoption of detachable bits will afford a reduction in
the "dollars and cents" of this feature of mining.
Items 2, 3, 4, and 5 are those which pertain to reconditioning
dull bits and a substantial saving may be gained if the operator
chooses that method most adapted to his special case.
Still further, since the drilling equipment of a mine represents an investment of a large sum of money, and as the life of
such equipment may be prolonged be efficient lubrication, a study of
eight different oils was undertaken.
It has been shown that the three sections of this report
4
deal with one of the fundamental operations of mining, namely;
drilling equipment and its maintainence. Efficient use of materials
in this operation will reward the operator amply and will enable him
to gain a greater return on his investment.
Section 1 of this report is given over therefore to a discussion of the manufacture of detachable bits in order to determine how
the manufacturing details of bits influence the service which the
bits give.
SECTION I
CHAPTER 111
BIT MANUFACTURING
Steel for bit manufacture.
Steel for use at the Hawkesworth
plant is purchased in bars one and three-eights inch round by eleven
feet long.
The composition of this steel is given by the following table.
Carbon
Manganese
1.05$ - 1.15$
— — —
Silicon
Phosporous
Sulfur
0.20$ - 0.30$
0.16$ - 0.25$
— — — —
0.025$
0.025$
Forging furnace. Preliminary to the forging operation, the
steel is heated in a standard open furnace. This is of brick construction and measures six feet sauare by four feet high and rests on
a stand four feet high, constructed of one-quarter inch angle irons.
The temperature of the furnace is maintained between nineteen
hundred and two thousand degrees Fahrenheit. Natural gas serves to
heat the furnace.
The furnace tender regulates the fuel intake by
means of a valve, inspection of the pyrometer determining the extent
he opens or closes the intake valve to maintain the proper temperature.
Heating of steel. Thirty bars of steel are placed in the
furnace in the morning as the shift comes to work.
It requires one-
half hour for the furnace to come to heat and the bars to reach the
proper forging heat. About four feet of the bar is heated at a time
and sixteen slugs may be sheared before the bar must be returned to
c
the furnace for reheating.
The forging furnace is shown in figure 1,
Figure 1
Figure 2
Forging operation. Located along side the furnace is the
Ajax forging machine. This machine is a product of the Ajax Mfg, Co,
The bar is withdrawn from the furnace by the operator aided
by four~Toot tongs. He rests the bar upon a support running along
the front of the furnace and over to the forging machine.
The bar is placed in the forging machine and butted against
a stop. A movable shear advances and shears a slug from the bar.
As contact between the slug and movable shear is made, a spring olip
clasps the slug which is then carried by means of the shear to the
7
forging die. One end of the slug is butted against a fixed die,
the movable die advances and the bit is forged. Then the movable
shear and movable die retreat, the clip is released and the bit falls
onto a steel conveyor. The operator again advances the bar to the
stop, trips the foot pedal, and the operation is repeated. Figure 2
shows the Ajax forger.
Pressing operation. The conveyor carries the bits to a Bliss
press where the flash of the bit is removed. The bits fall from the
conveyor to a basket from whence they are taken by the press operator
and placed in the die of the press. This die has the shape and
dimensions of the starter bit. The bit is placed skirt down in the
die and a punch having a face similar to that of the bit is forced
down.
This pushes the bit through the die, thus removing the flash.
Bits which have cooled too much for this pressing operation by the
time they reach the press are set aside in a container and when a
sufficient amount has accumulated, they are reheated. The motion of
the punch is controlled by a foot pedal manipulated by the operator.
An electric motor is attached by means of a multiple "V" belt drive
to a three and one-half foot flywheel. This wheel is rotating continuously and the foot pedal serves to engage the flywheel and
punch through a cluteh,arrangement. When the clutch is released,
the punch falls of its own weight. The clutch is engaged to raise
the punch.
After removal of the flash, the bit falls to a container for
removal to subsequent treatment. Figure 3 shows the Bliss press.
7a
Figure 3
HSfOi
Figure 4
8
Figure 4 shows the steps in bit forging and pressing, namely, slug,
slug with flash adhering, slug with flash removed, flash, and bit
ready for annealing.
Annealing.
The heating of the steel previous to forging en-
larges the grain size to an extent which would if no subsequent heat
treatment were given the bit, produce an unsatisfactory product. Also
in the forging operation, flow lines have been set up in the bit
which would cause it to fail upon use. To reduce the grain size
and remove the flow lines, a subsequent form of heat treatment is
given the bits in that they are placed in an electric furnace for
annealing.
Thirty five hundred bits are placed in the furnace and brought
to a temperature of fourteen hundred degrees fahrenheit.
The tem-
perature here is automatically controlled by a relay setup. Heating is done by means of four electric coils and the relay setup
serves to hold the temperature constant at fourteen hundred degrees
Fahrenheit. It requires four hours to bring the furnace up to heat
and the bits are held at the proper temperature for four hours.
The furnace is then shut down and the bits allowed to cool to room
temperature. Figure 5 shows the electric annealing furnace.
Machine shop work. After the bits have cooled, they are
removed to the five station milling machine. Figure 6 shows this
machine.
Figure 7 is a view of the interior showing the drills
which machine the bit.
The milling machine is a product of the
Goss and DeLeeuw Co. of New Britain, Conn.
r
Figure 5
Figure 6
Figure 7
Figure 8
10
The milling machine is equipped with two electric motors.
One of these serves to drive the carriage back and forth, the
other causes the drills to rotate. Figure 8 shows the motor and
of the machine.
The miller is equipped with five arms powered by motor
number one. ^he rotation of these arms serves to place each bit
in five different positions, at each of which a specific operation
is performed on the bit. When the operation is finished at respective position, the carriage retreats, arms rotate, the bit is thus
advanced to the next position at which point the following operation is performed on it.
The sequence of operations may be best shown by tracing a
specific bit through the entire process.
At position 1 the bit is placed in the vise which is then
tightened upon it. As the machine retreats, the arms rotate and
the bit is advanced to position 2. Now the machine advances and
the hole for the shank is drilled in the bit. This is performed
by a two flute drill and the hole is fifteen-sixteenths of an inch
in diameter and drilled to a depth of twenty-nine thirty-seconds
of an inch. After rotation of the arms the bit is moved to position 3. At this step the hole is bottomed, or given a square
surface and reamed to a diameter of one and one-sixty fourth inch.
This is accomplished by a four flute drill. At position 4, the
center hole for water is drilled, the diameter being seven-thirty
seconds of an inch.
This is accomplished
by means
of a
11
two flute drill. The hole is drilled to such a depth that the
point of the drill barely breaks through the surface of the outting
face of the bit. The hole is not drilled entirely through the bit
because such a practice would result in the drill being broken.
Also, in later sharpening operations, the surface of the cutting
face is removed to such a depth that the hole is exposed. This
scheme serves to prolong the life of the milling machine drills and
the grinding operation serves to open the hole effectively. At
this position the skirt of the bit is chamfered to remove the rough
edges.
This provides a bevelled rather than a square surface, thus
making for easier removal of the drill steel from the drill hole
after drilling to a specific depth has been completed.
The fifth
and last step is the threading of the bit with left hand threads
having a pitch of four threads to the inch.
The entire operation
consisting of five operations requires two and one-quarter minutes
per bit.
This then concludes the steps taken in production of detachable bits.
The following section will be given over to the grind-
ing proceedure and subsequent heat treatment as practiced in this
plant.
SECTION 11
BIT RECONDITIONING
CHAPTER IV
GENERAL CONSIDERATIONS AND DEFINATIONS OF TERMS USED
It is the purpose of this section of the report to present a
study of mechanical grinding, hot milling, and hand grinding as
methods for reconditioning detachable bits.
The drill bit may rightfully be claimed to be the most critical factor in rock drilling performance. The drill and its mounting, once decided upon, may be expected to give quite uniform results from one shift to another with only occassional failure of serious nature. The drill bit, however, is called upon to drill only
a few inches of rock before it is resharpened and rehardened. As
a result, the human element plays a big part in bit performance and
a high overall efficiency in rock drilling requires intelligent
supervision in the reconditioning shop. Competant work here will
result in an increased number of inches of hole drilled per bit.
Drilling action. The drilling action of a rock drill embodies two main actions. There is a reciprocating motion whereby the
drill shank receives blows from the anvil block of the drill. This
shock is transmitted through the shank and causes the bit to be driven into the rock.
A rotary action of the drill bit reams out the hole and shifts
the cutting edges thus affording a fresh surface upon which the
cutting edges of the bit strike.
SHARP 3IT
Reaming
Edges
Reaming
Surface
Beaming
Points
Clearance
Oroore
Ving
Thickness
Figure 9a-.
A
Dotted Line Indicates
Sharp Edge Previous
Tp.-Drilling..
Showing Rtfoaded Cutting1
Edges and Beaming'Points
-«—-E-Mjiujse^ia-.
.B«
14
The chipping and reaming action during drilling cause the cutting edges of the bit to become dull and also results in a loss of
gauge of the bit.
One readily sees that as the bit loses gauge and the cutting
edges become dull, it must be replaced by a sharp bit. The sharp
bit in turn must have a gauge not to exceed that residual in the bit
which it replaces. Although there is a slight amount of "overdrilling"
in the hole due to the joggling of the bit in the hole, for all
practical purposes, we can state that each succeeding bit should
have a smaller gauge than the one proceeding it.
Reference is made to figure 9a. wherein are labeled the important features of a detachable bit. Figure 9b. shows the conditions existing in a dull bit.
It is necessary therefore by a combination of face sharpening
and gauging to recondition the bit and restore the sharp cutting
edges and reaming edges.
General sharpening practice. Reference is again made to
figure 9b.
There are two ways of restoring the cutting edges and reaming surfaces. Metal can be cut away from the head of the bit thus
pointing it along the line BB». On the other hand, the bit may
be given a scanty facing operation, barely enough to sharpen the
cutting edges over a minimum of their length, and the rest can be
removed from the gauge, thereby pointing the bit along the line AA'.
Too heavy cuts from the face of the bit will lead to a break through
into the hole for the shank after a few sharpenings. On the other
hand excessive cuts from the gauge will reduce the cross section of
the bit, approaching the shank diameter to such an extent that the
15
bit is no longer fit for drilling.
Obviously a happy medium exists between these two extremes.
Since most of the metal of a bit is contained in the head, good sharpening proceedure should require that the heavier cut be taken from
the face of the bit, followed by the lighter edging cut.
Mechanical grinding is so termed because much of the work
performed manually in other plants is here done by machines
and hence a closer control may be exercised throughout the process
leading to a more satisfactory product.
Hot milling performs the function of redressing the bit, at a
suitable forging temperature, by the removal of metal from the flutes
with a milling cutter followed by a similar cut from the bit gauge.
Hand grinding, perhaps the simplest method of sharpening,
redresses the bit by a combination of face sharpening and gauging.
Using a suitable holder, the bit face is held against the abrasive
wheel and metal removed from between the flutes of the bit so as to
sharpen the cutting edges. This operation is then followed by gauging.
CHAPTER V
MECHANICAL GRINDING
This method is termed mechanical grinding because much of the
work performed manually in other plants is here done by machines.
The grinding room contains six grinding units as shown in
figure 10. A close up of the grinding unit is shown in figure 11.
Figure 10
Both newly forged bits and dull bits are sharpened here.
The new bits are faced but not edged. Regrinds must be both faced
and edged.
17
Figure 11
Bit Sorting. Regrinds are sorted at the various mines for
gauge size. Upon arrival at the plant they are sorted for height.
They are sized for height so that the sharpening operation necessitates the removal of only one-thirty second of an inch with each
cut.
It will be shown later how the light cut is advantageous.
Figure 12 illustrates the type of channel used to sort bits
for height.
The bit is placed in the channel and moved as far as possible
toward the small end.
The channel is stamped with the various
heights of bits corresponding to each gauge size, and the point
at which the bits stops determines its height. This bit is then put
18
Figure 12
in a container with bits of similar height.
As a sufficient number of bits alike as to height and gauge
accumulate they are taken to one of the grinding units. The machine
is set for this size bit and the lot is ground.
Description of grinding unit. There are six grinding units,
The drums and abrasive wheels are supported on a base four and onehalf feet wide, six and one-half feet long and three feet high.
The facing and edging drums are connected by belt drives to onehalf horsepower electric motors. The drums make one revolution per
two and one-half minutes. The abrasive wheels of which there are
four per facing drum and one per edging drum (each unit) are conn-
19
ected by " V belt drives to twenty horsepower electric motors.
The speed of abrasive wheels is twelve hundred revolutions per
minute.
All grinding here is wet grinding. A one-quarter horsepower
electric motor drives the centrifugal pump which circulates the
grinding oil. The function of the oil is to prevent the burning
of the steel in grinding by carrying away the cuttings, thus preventing small fragments of metal accumulating between the grains of
the abrasive wheel, which would in turn cause the rubbing of metal
on metal.
Secondly, the oil serves as a lubricant.
Bit holders, Two types of bit holders are utilized. The
Type "A" holder is used on the newly forged bits and had to be
adopted because the center hole is not drilled entirely through the
bit. (See page 10) In this type, the jaw is stationary and of
such a size as to fit snugly inside the skirt of the bit. To
place the bit on the holder, the holder is first inserted in a slot
of the workbench. It rests on the collar and protrudes above the
level of the bench.
The bit is driven down over the jaw by strik-
ing the face of the bit with a hammer. Simultaneously, the clips
fasten on the outside of the bit skirt. To remove the bit from the
holder, the bottom of the holder is struck a blow, the pin in the
center of the holder is forced up thus driving the bit from the holder.
The type "B" holder is used on all grinding units except
that engaged in facing newly forged bits.
This holder is placed
20
in the slot of the workbench and rests on the collar. This holder
is equipped with a movable jaw. The bit is placed on the holder and
a steel punch inserted through the center hole. The punch is struck
a blow and forces the steel center pin down in the holder thus
spreading the movable jaws which grip the bit securely.
To remove
the bit from the holder it is only necessary to strike the bottom
of the holder. This causes the pin, which projects past the bottom
of the bit holder, to be forced up thus allowing the jaws to collapse
and the bit falls from the holder.
Facing operation. This operation is performed to sharpen
the cutting edges of the bit. After forty bits have been placed
on the holders, the holders are dropped into the slots of the
facing drum. The rotation of the drum carries the bit into contact
with the abrasive wheel where one-quarter of the bit is ground (that
portion between two adjacent wings).
The abrasive wheel has a
bevelled face corresponding to the taper between the wings of the
bit. After passing the abrasive wheels, the bits and holders
revolve automatically and the next contact between wheel and bit
sharpens another one-quarter of the bit. Four complete revolutions of the drum are needed to sharpen each bit.
The revolution of the holder and bit is accomplished in
the following manner. The forty sockets into which the bit
holders fit, penetrate towards the center of the facing drum similar to spokes of a wheel. The bottom of each socket is equipped
with teeth radiating from the socket. After the bit passes the
21
abrasive wheel, those teeth enter grooves which are running at an
angle to the path of the drum.
These grooves are stationary and
the travel of the socket teeth through them force the socket to
turn thus the bit holder and bit rotate ninety degrees. This process
is repeated for four revolutions of the drum and the bit is then
completely faced.
A unit in which the facing operation only is performed on
bits, produces fourteen hundred seventy five bits (1475) per day
Ceight hours). A unit doing both facing and edging will recondition eight hundred fifty bits per eight hour shift. The abrasive
wheels need from one to four dressings per shift. A facing wheel
will last for six thousand to seven thousand bits and edging wheels
for fifteen thousand bits.
Edging or gauging operation. After forty bits have been
face sharpened, they are removed from the facing drum and twenty
two of them are placed in the edging drum.
There is a specific
reason for the different capacities of the facing and edging drums.
As has already been stated, if the gauge of the bit has been reduced one-sixteenth on an inch while in service, it is necessary
to place the bit in the edging drum and reduce it to the next
smaller size. It has been found that roughly only one-half of
the ground bits need edging, hence the twenty two bit edging drum.
Rotation of the drum serves to bring each bit into contact
with the abrasive wheel. After passing the abrasive wheel, a
22
gear arrangement r o t a t e s the b i t so t h a t on the following contact
between wheel and b i t , another portion of the b i t i s ground.
I
CHAPTER VI
HARDENING & TEMPERING
As the sharpening of a bit is completed, it is placed in
a container with bits alike as to gauge and height. As a sufficient quantity of bits of like gauge and height accumulate, they
are taken to the tempering units.
There are two similar hardening units, one for new bits
and one for regrinds. The duplicate sets of pots are, necessary
because of the two different ranges of temperatures utilized for
new and reground bits.
The different temperatures are in turn
necessitated because of the different amounts of metal contained
in the bits. A higher temperature is required for the bulkier
new bit,
^
Each tempering unit consists of two furnaces, one quenching tray, and one tank of warm water to give the bits a partial
draw after quenching.
Furnaces, Heating of the bits is accomplished in pot furnaces utilizing a molten bath of liquid salts.
Figure 13 shows a general view of the hardening set up and
figure 14 is a view down into one of the furnaces with the pot
removed exposing the heating element.
The pot£ have a circular base forty inches high and forty
inches in diameter. On top of the base rests a collar into which
the pot fits.
The pot is eighteen inches deep and fourteen inches
in diameter. It is composed of a refractory and is surrounded
24
by electric coils which are the heating element. The coils heat
the pot which in turn heats the liquid. One inch below the top
of the liquid level there is a punched steel plate upon which the
bits rest.
Figure 13
Figure 14
Quenching tray. The quenching "tray measures forty four
inches by thirty inches and consists of fourteen, three inch pipes
which are covered by screens upon which the bits rest. Circulating through the pipes is a moving current of water.
This moving
current of water is used because it keeps the water cold and reduces the possibility of soft spots being found in the bits after
hardening.
If the water were not moving, it would become heated
25
as the operation progressed and more and more bits had been added
to the tray, the hot bits gradually raising the temperature of the
water. Also were the current of water not moving, there would be
the tendency for steam to collect in the depressions between the
cutting edges and thus produce a soft spot on the bit.
The flow of water is controlled by a master valve on the
main line and secondary valves on each individual pipe. The
master valve admits water to the entire system and the secondary
valves control the amount.
This scheme of secondary valves is
necessary to assure a definate height of water over each pipe.
Were not the secondary valves used it is readily seen that the
first pipe would receive most of the water, the second less, the
third still less, and so on down the line. By having the secondary valve on each successive pipe opened slightly more than the
one on the pipe preceeding it, a uniform height of water is maintained throughout the entire tray. A uniform height of water is
necessary so that each bit receives the same depth of hardness.
Were not the secondary valves used, in order that the bits fartherest down the line receive the proper depth of hardness, the height
of water on the first bits would have to be so great as to cover
i
the skirt of the bit. This would produce the effect of making
the bits susceptible to breakage upon use. It is for this reason
also that the entire bit is not immersed in cold water. If cold
water were allowed to come in contact with the entire bit, the
26
seat against which the shank butts would become unnecessarily hard.
This would lead to fracture of the bit with the hammering of the
shank with drilling. Rather a tough steel is desired here with
a hard steel being the cutting edges.
Method of hardening and tempering. Reference is made to
figure 15. The tempering process consists of placing the bits in
the first pot furnace containing molten lead where they are given
a preheat. The temperatures here are eleven hundred degrees fahrenheit for new bits and one thousand degrees fahrenheit for regrinds.
The second pot contains Houghton Liquid Heat #6, a mixture of thirty
five percent sodium carbonate, thirty five percent sodium cyanide
and thirty percent sodium chloride. Bonnets over the heating pots
serve to remove fumes which might be harmful to the operators.
The bits are taken from the lead pot and transferred to the salt
bath where they are heated to fourteen hundred and forty degrees
fahrenheit for new bits and fourteen hundred and twenty degrees
fahrenheit for regrinds. The temperature of the baths is kept constant by pyrometers which operate an electric relay system and
serves to turn the heat on or off.
The bits are kept in each bath^ three minutes. The time of
immersion is regulated by a clock and electric light bulb arrangement. Mounted above the heating unit is a red globe and a green
globe.
These globes are connected by an electric relay system to
a clock so that every one and one-half minutes the light changes
Incoming
Doll Bits
•
V
>
-
t
Grinding
#1
#2
#3
#4
?S
Units
>'
•>'
^
<f
Lead
Furnaces
X
Salt
Furnaces
Quenching
Trays
Draving Tanks
''
•
Out Going Sharp B i t s
Figure 15
'
28
from red to green or vice versa.
The pots hold twenty eight bits
and fourteen of these are run on the red cycle and fourteen on the
green cycle.
At the beginning of the shift when operations commence and
the furnace is up to heat, the bits are brought in for hardening.
As the light changes from green to red, fourteen bits are placed
in the red section of the lead bath. After one and one-half minutes, the light changes from red to green and fourteen bits are
added to the green section of the lead pot. As the light changes
again, the charge in the red section of the lead pot, having been
heated for a total of three minutes, is transferred to the red
section of the lead bath.
Fourteen bits are placed in the red
section of the lead bath to take the place of those just removed.
With another light change, the bits from the green section are
transferred from the lead to the salt bath, fourteen bits being a
added to the green section of the lead bath. The following light
change brings the bits from the red section of the salt bath onto
the quenching tray and each section along the cycle is advanced
one step•
The bits remain on the quenching tray for about thirty seconds at which time the red color has disappeared and they are throvm
into the tank of warm water where a partial draw is accomplished
which serves to relieve the strains imparted in hardening and to
remove the salt crust which the bits picked up in the heating pot.
CHAPTER Vll
BIT TESTING
System followed.
In order to further the comparison between
the three methods of reconditioning bits, underground work was
carried out whereby the bits were put into use in the mine under
actual mining conditions. The bits were taken from stock bins and
were judged as being representative of the average A, C M . bit.
Bits chosen consisted of five each of seconds, thirds, fourths,
and fifths. These bits were marked so that each bit could be identified.
Marking of bits.
The bits were first marked on an abrasive
wheel according to gauge size. Two marks denoted second gauge,
three marks denoted third gauge, and so forth. The bits were then
marked with another identifying notch depending upon which bit of
a gauge series it happened to be. For example, the mark 2-1 on a
bit meant that this bit was number one of the series which had an
initial gauge size of second.
3-1 meant the number one bit of the
third gauge size series. In this way a definate record could be
kept of each bit.
The proceedure followed in testing may be enumerated as
follows:
1. After selection of bits from the stock bin they are
measured for gauge and height.
2.
The bits are dulled by usage underground.
3.
They are measured again to determine the wear incurred
in usage.
4.
The bits are reconditioned.
30
5. After sharpening, the bits are again measured before
further use.
6.
The bits are again put into use and the above proceedure
repeated.
A record was kept of each bit and the following data were
obtained as a result of the testing.
1.
Loss of gauge and height with each usage,
2.
Drilling speed.
3. Distance drilled per bit.
4.
Decrease in gauge and height with each sharpening.
5. Percent of bits remaining in the same size following
each sharpening and percent going to smaller sizes.
6.
Total number of regrinds obtained from the set of bits
7. Other factors as breakage and so forth, deemed pertinent
to the particular method of reconditioning.
Measuring bits. Previous to use, the overall height and
gauge of the bit was measured.
Following usage the overall height
and gauge were taken to determine the wear of each bit with use.
In addition, the cutting edge residual in the bit, following use of
the bit, was measured.
This was done in order to represent the
wear of the reaming point of the bit. The difference between "gauge
before drilling" and "length of cutting edge after drilling" represents the wear of the reaming point.
Following are tabulated the series of tests performed on the
mechanical ground bits.
31
Test # 1
Bit No.
Gauge
Before
Drilling
Height
Before
Drilling
Gauge
After
Drilling
Length of
Cutting
Edge
After
Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
30/32
30/32
28/32
30/32
28/32
24/32
24/32
26/32
24/32
24/32
20/32
20/32
22/32
22/32
20/32
16/32
16/32
18/32
18/32
16/32
26/32
30/32
31/32
15/32
28/32
29/32
22/32
24/32
26/32
22/32
24/32
24/32
20/32
26/32
20/32
20/32
20/32
20/32
20/32
20/32
29/32
29/32
28/32
30/32
28/32
22/32
24/32
24/32
24/32
22/32
20/32
22/32
22/32
20/32
16/32
16/32
16/32
16/32
16/32
16/32
24/32
22/32
28/32
30/32
28/32
20/32
22/32
26/32
28/32
18/32
18/32
20/32
22/32
22/32
20/32
16/32
14/32
18/32
18/32
16/32
Height
After
Drilling
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
26/32
30/32
31/32
15/32
28/32
28/32
22/32
24/32
26/32
22/32
22/32
24/32
20/32
26/32
20/32
18/32
18/32
20/32
20/32
20/32
Remarks
Not used*
Not used*
Not used*
Not used*
Not used*
Not used*
Broken
Not
Not
Not
Not
used*
used*
used*
used*
Not used*
Not used*
Not used*
Drilling Distances
Bit Gauge
Second
Third
Fourth
Fifth
Total
No. Bits Used
Total Distance
Drilled Inches
Ave. Dist. Drill
Drilling Per Bit
Speed
Time Min. Used
In,/i/Iin,
62
124
192
126
2
2
1
2
816
96
8.5
General Remarks. Test #1 was carried out in 1027-29 stope at the
Orphan Girl mine. The ground was soft, resembling fault gouge. At
the conclusion of this test it was decided that the ground was too
soft to give the bits rough usage. For this reason the field of
operations was transferred to the Leonard mine. Due to the softness of the ground only seven bits were used to drill the round.
Bits marked with an asterisk were not used, however, they were used
in test #2 which appears on a following page.
32
Test #2
Bit No,
Gauge
Height
Before
Before
Drilling Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
30/32
30/32
28/32
30/32
28/32
24/32
24/32
26/32
24/32
24/32
20/32
20/32
22/32
22/32
20/32
16/32
16/32
18/32
18/32
16/32
Bit Gauge
No. Bits Used
In Test
26/32
30/32
31/32
30/32
28/32
29/32
22/32
24/32
26/32
22/32
24/32
24/32
20/32
26/32
20/32
20/32
20/32
20/32
20/32
20/32
Second
Third
Fourth
Fifth
3
3
4
3
Total
13
Gauge
After
Drilling
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
29/32
29/32
27/32
29/32
27/32
22/32
22/32
25/32
23/32
22/32
20/32
20/32
21/32
22/32
20/32
16/32
16/32
16/32
18/32
16/32
Total Distance
Drilled Inches
24/32
22/32
24/32
25/32
24/32
20/32
19/32
18/32
17/32
18/32
18/32
15/32
16/32
16/32
17/32
20/32
16/32
11/32
10/32
12/32
26/32
30/32
30/32
29/32
27/32
28/32
20/32
23/32
25/32
22/32
22/32
23/32
19/32
25/32
18/32
20/32
18/32
19/32
18/32
19/32
Remarks
Not used*
Not used*
Not used*
Not used*
Not used*
Not used*
Not used*
Distance
Drilling Drilled
Time Min. Per Bit
Drilling
Speed
In./Min.
34
24
34
90
578
79.1
7.3
General Remarks. Test #2 was carried out in 3137-56 stope at the
Leonard mine. The ground was quartz stringered with chalcocite.
Those bits which had not been used in the previous test at the
Orphan Girl mine were put into use in this test. Bits marked with
an asterisk are those which had been used in Test #1.
33
Test #3
Gauge
Before
Bit No. Drilling
Height
Before
Drilling
Gauge
After
Drilling
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
24/32
28/32
28/32
30/32
28/32
28/32
22/32
22/32
24/32
20/32
28/32
22/32
20/32
26/32
20/32
20/32
16/32
18/32
20/32
22/32
1 28/32
1 24/32
1 24/32
1 24/32
1 22/32
1 20/32
1 24/32
1 28/32
1 26/32
1
1
1
1
1
24/32
20/32
20/32
18/32
18/32
1
1
1
1
1
18/32
16/32
16/32
14/32
14/32
1
1
1
1
1
16/32
16/32
18/32
20/32
1
1
1
1
12/32
12/32
12/32
14/32
14/32
14/32
16/32
14/32
16/32
1
1
1
1
1
12/32
10/32
14/32
10/32
12/32
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
562
5-3
5-4
5-5
28/32
26/32
26/32
28/32
26/32
20/32
22/32
20/32
20/32
20/32
16/32
18/32
20/32
22/32
20/32
16/32
16/32
18/32
16/32
16/32
Bit Gauge
No. Bits Used
In Test
Second
Third
Fourth
Fifth
Total
Remarks
Broken
26/32
28/32
22/32
20/32
24/32
Broken
Total Distances
Drilled Inches
24/32
20/32
16/32
24/32
— 20/32
16/32
17/32
18/32
20/32
Lo st
Distance
Drilling Drilled
Time Min, Per Bit
5
4
5
5
Drilling
Speed
In./Min.
16
20
17
17
330
36.7
9.0
General Remarks. This test was performed following the first mechanical regrind. Drilling was done in 3137-56 stope at the Leonard mine.
The ground was similar to that encountered in the preceeding test.
34
Test #4
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge
Before
Drilling
Height
Before
Drilling
Gauge
After
Drilling
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
26/32
24/32
24/32
28/32
26/32
20/32
22/32
20/32
16/32
22/32
24/32
24/32
24/32
22/32
24/32
20/32
18/32
18/32
Total
20/32
18/32
20/32
20/32
20/32
18/32
14/22
18/32
14/32
1
1
1
1
1
1
1
1
1
22/32
24/32
22/32
22/32
20/32
24/32
16/32
18/32
18/32
_______
_______
_______
_______
________
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
16/32
16/32
16/32
20/32
20/32
18/32
16/32
20/32
14/32
16/32
16/32
20/32
10/32
14/32
12/32
16/32
Broken
18/32
16/32
14/32
20/32
Lost
1 16/32
1 16/32
1 16/32
1 16/32
1 16/32
1 14/32
1 10/32
1 14/32
_______
_______
_______
_______
1 20/32
1 20/32
1 20/32
1 16/32
1 16/32
1 14/32
1 14/32
1 14/32
1 12/32
1 20/32
1 20/32
1 16/32
No. Bits Used
Bit Gaug;e In Test
Second
Third
Fourth
Fifth
24/32
24/32
24/32
24/32
24/32
20/32
18/32
20/32
16/32
Remarks
Total Distance
Drilled Inches
Reject
Distance
DrillirLg Drilled
Time Min. Per Bit
1
4
4
8
Drilling
Speed
In./Min.
17
18
19
19
317
17.2
18.4
General Remarks. Test #4 was carried out in 3137-56 stope at the
Leonard mine. The ground was similar to that in preceeding tests,
The high drilling speed is probable due somewhat to the fact that
a newly reconditioned drill was used to drill this round.
35
Test #S
Gauge
Before
Bit No. Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
562
5-3
5-4
5-5
Height
Before
Drilling
20/32
22/32
22/32
22/32
20/32
20/32
16/32
20/32
16/32
Gauge
After
Drilling
20/32
18/32
18/32
20/32
20/32
18/32
16/32
18/32
20/32
Length of
Cutting
Height
Edge
After
After
Drilling
Drilling
18/32
18/32
16/32
18/32
18/32
20/32
16/32
16/32
16/32
20/32
20/32
20/32
22/32
20/32
18/32
16/32
18/32
14/32
16/32
16/32
14/32
16/32
16/32
14/32
12/32
12/32
10/32
14/32
14/32
14/32
16/32
1 8/32
1 10/32
1 10/32
1 14/32
1
1
1
1
1 14/32
1 12/32
1 12/32
1 16/32
1 20/32
1 16/32
1 16/32
1 16/32
1 14/32
1 16/32
1 16/32
•Broken test #3
**Lost test #3
•••Broken test #3
••••Lost test #5 following usage.
20/32
10/32
1 8/32
1 16/32
—
Bit Gauge
Second
Third
Fourth
Fifth
Total
Remarks
Broken*
14/32
16/32
16/32
18/32
1
1
1
1
14/32
16/32
12/32
18/32
1
1
1
1
12/32
16/32
16/32
18/32
Lost**
1 14/32
1 12/32
Broken***
No. Bits Used
In Test
Total Distance
Drilled Inches
Lost****
Distance
Drilling Drilled
Time Min. Per Bit
0
0
8
9
Drilling
Speed
In./Min.
0
0
19
19
323
38
8.5
General Remarks. Test #5 was performed following the third mechanical
regrind. Drilling was done in 3137-56 stope at the Leonard mine. The
character of the ground v/as similar to that in proceeding tests.
36
Test #6
Bit No.
2-1
2-2 ,
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4_5
Gauge
Before
Drilling
1
1
1
1
1
1
1
1
1
Height
Before
Drilling
18/32
22/32
18/32
22/32
18/32
16/32
16/32
16/32
14/32
18/32
20/32
14/32
16/32
16/32
18/32
16/32
14/32
14/32
Gauge
After
Drilling
Length of
Cutting
Edge
After
Drilling
Height
After
Drilling Remarks
16/32
20/32
1 12/32
1 16/32
16/32
16/32
20/32
16/32
14/32
14/32
16/32
14/32
16/32
14/32
10/32
12/32
14/32
10/32
14/82
16/32
16/32
14/32
12/32
14/32
••
•••
***
1 14/32
1 16/32
5-1
10/32
16/32
1 16/32
1 16/32
1 10/32
1 12/32
1 10/32
1 14/32
12/32
1 14/32
1 10/32
1 10/32
18/32
1 16/32
1 14/32
1 18/32
_______
1 14/32
••
5-3
1 16/32
5_5
•Lost, test #6
••Broken, test #3
•**Reject, grind #4
****Lost, test #3
*****Lost, test #5
Bit Gauge
Second
Third
Fourth
Fifth
Total
*••*
No. Bits Used
In Test
•••
*****
Total Distance
Drilled Inches
Distance
Drilling Drilled
Time Min. Per Bit
Drilling
Speed
In./sline
0
0
19
19
0
0
5
8
247
26.5
9.3
General Remarl s. Test #6 was performed following the fourth mechanical
regrind. The test took place in 3137-56 stope at the Leonard mine.
The ground wa.: similar to preceeding tests.
37
Test #7
Bit No,
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge
Before
Drilling
Height
Before
Drilling
1 14/32
1 18/32
1 14/32
1 16/32
1 14/32
1 14/32
—
*
1 14/32
1 14/32
1 12/32
1 14/32
_
— —
1 16/32
1 16/32
1 16/32
*••
_-__- —
____——
____——
•**
*•**
*****
wm __ — -
l(t ](ej(C)|C Sft
-_-• -•-
___
— — —
________
__—___.
____—_
1 14/32
***
*••
******
***
****
1 16/32
._
._
No, Bits Used
Bit Gauge In Test
Total
1 18/32
1 14/32
*•
**•
***
•Lost, test #7
**Lost, test #6
•••Reject, grind #5
••••Broken, test #3
Second
Third
Fourth
Fifth
Gauge
After
Drilling
Length of
Cutting
Height
Edge
After
After
Drilling Remarks
Drilling
*****
*******
•••••Reject, grind #4
***#**Lost, test #3
*******Lost, test #5
Total Distance
Drilled Inches
Distance Drilling
Drilling .Drilled
Speed
Time Min. Per Bit In./foin.
0
0
0
4
19
76
8.7
8.7
General Remarks. This was the concluding test performed with mechanical ground bits. It was conducted in 3137-56 stope at the Leonard
mine under conditions similar to preceeding tests. It is seen from
the table on this page how the bits reacted to the test. The history
of each bit and what happened to it are explained by the comments
marked by asterisks. The three bits not marked were rejected following this test as being too short for further reconditioning.
CHAPTER Vlll
BIT RECONDITIONING
The following section of the report contains those tables
pertinent to the sharpening of the bits by mechanical grinding.
As the set of bits was dulled it was returned to the shop
to be sharpened.
Following sharpening the bits were again meas-
ured previous to use in a following test.
Strictly speaking, bit sizes are as follows* Starter-2",
Second-1 7/8", Third-1 3/4", Fourth-1 5/8", Fifth- 1 l/2". However because of the overdrilling and the slight enlargement of
the hole thereby, it is possible for a hole to be drilled without
this hard and fast rule for changing bits.
For this reason any
bit which varied by not more than one-sixteenth inch minus from
its regular size was still classed as that size.
Table #2 is a recapitulation of bit sizes following each
grind. It gives the percentage of bits which will yield another
service at the same gauge size, and also, the percentages of bits
which moved down one or more sizes.
_-\*if*-i_Cj
-***___•'*__. «* .
39
Mechanical Grind #1
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
5-4
3-5
4-1
4-2
4©3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
1 28/32
1 26/32
1 26/32
1 28/32
1 26/32
1 20/32
1 22/32
1 20/32
1 20/32
1 20/32
1 16/32
1 18/32
1 20/32
1 22/32
1 20/32
1 16/32
1 16/32
1 18/32
1 16/32
1 16/32
Height after
Sharpening
1 24/32
1 28/32
1 28/32
1 30/32
1 28/32
1 28/32
1 22/32
1 22/32
1 24/32
1 20/32
1 28/32
1 22/32
1 20/32
1 26/32
1 20/32
1 20/32
1 16/32
1 8/32
1 20/32
1 22/32
Remarks
Still second
Still second
Still second
Still second
Still second
Still third
Down to fourth
Down to fourth
Broken in drilling, test #1
Down to fifth
Still fourth
Still fourth
Still fourth
Still fourth
Still fourth
Still fifth"
Still fifth
Still fifth
Still fifth
Still fifth
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
Variation
Second to second
Second to third
Second to fourth
Second to fifth
Second to reject
Third to third
Third to fourth
Third to fifth
Third to reject
Fourth to fourth
Fourth to fifth
Fourth to reject
Fifth to fifth
Fifth to reject
Percent
100
0
0
0
0
20
80
0
0
80
20
0
100
0
Remarks
Mechanical Grind #2
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
Height After
Sharpening
1
1
1
1
1
1
1
1
1
26/32
24/32
24/32
28/32
26/32
20/32
22/32
20/32
16/32
1
1
1
1
1
1
1
1
1
22/32
24/32
24/32
24/32
22/32
24/32
20/32
18/32
18/32
1
1
1
1
16/32
16/32
16/32
20/32
1
1
1
1
20/32
18/32
16/32
20/32
1 16/32
1 16/32
1 16/32
1 16/32
1 16/32
1 20/32
1 20/32
1 16/32
Remarks
Still second
Down to third
Down to third
Still second
Still second
Down to fourth
Still fourth
Down to fourth
Down to fifth
Broken, test #1
Down to fifth
Down to fifth
Down to fifth
Still fourth
Lost, test #3
Still fifth
Broken, test #3
Still fifth
Still fifth
Still fifth
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifth
Variat ion
Second to second
Second to third
Second to Fourth
Second to fifth
Second to reject
Third to third
Third to fourth
Third to fifth
Third to reject
Fourth to fourth
Fourth to fifth
Fourth to reject
Fifth to fifth
Fifth to reject
Percent
Remarks
60
40
0
0
0
0
100
0
0
43
43
14
67
33
Lost
Mechanical Grind #3
Table #1
Bit No.
2-1
2-2
2-3
2©4.
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
Height After
Sharpening
1
1
1
1
1
1
1
1
1
20/32
22/32
22/32
22/32
20/32
20/32
16/32
20/32
16/32
1
1
1
1
1
1
1
1
1
20/32
18/32
18/32
20/32
20/32
18/32
16/32
16/32
20/32
1
1
1
1
14/32
16/32
16/32
18/32
1
1
1
1
14/32
16/32
12/32
18/32
Fourth
Third
Third
Third
Fourth
Fourth
Fifth
Fourth
Fifth
Broken, test #1
Fifth
Fifth
Fifth
Fouth
Lost, test #3
Fifth
Broken, test #3
Fifth
Fifth
Fifth
_______
1 14/32
1 12/32
________
1 16/32
1 16/32
1 16/32
Remarks
1 20/32
1 16/32
1 16/32
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
Variation
Second to second
Second to third
Second to fourth
Second to fifth
Second to reject
Third to •third
Third to .fourth
Third to fifth
Third to reject
Fourth to fourth
Fourth to fifth
Fourth to reject
Fifth to fifth
Fifth to rej ect
Percent
0
33
67
0
0
67
0
33
0
100
0
0
100
0
Remarks
42,
MechanicaJ Grind #4
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5~1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
Height After
Sharpening
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
18/32
22/32
18/32
22/32
18/32
16/32
16/32
16/32
14/32
18/32
20/32
14/32
16/32
16/32
18/32
16/32
14/32
14/32
Fourth
Third
Fourth
Third
Fifth
Fifth
Fifth
Fifth
Fifth
Broken, test #3
Reject, grind #4
Reject, grind #4
Fifth
Fifth
Lost, test #3
Fifth
Broken, test #3
Fifth
Reject, grind #4
Lost, test #5
___
1 14/32
1 16/32
1 10/32
1 16/32
_______
_______
1 14/22
1 12/32
1 16/32
1 18/32
Remarks
_______
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
Variation
Second to second
Second to third
Second to Fourth
Second to fifth
Second to reject
Third to third
Third to fourth
Third to fifth
Third to reject
Fourth to Fourth
Fourth to fifths
Fourth to reject
Fifth to fifth
Fifth to reject
Percent
0
0
0
0
0
67
33
0
0
20
80
0
55
45
Remarks
•
•
•
•
*
•*
•Previous grinding had reduced the bits to all below the second size.
••Of the 45% of the fifth bits going to reject, 75% of these were
rejected by virtue of being too small to sharpen and 25% were lost in
the previous underground test.
43
Mechanical. Grind #5
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
Height After
Sharpening
1 14/32
1 18/32
1 14/32
1 16/32
_______
___—__
_______
___
___—__
1 14/32
1 14/32
Fifth
Fourth
Lost, test #6
Reject, grind #5
Reject, grind #5
Fifth
Reject, grind #5
Reject, grind #5
Reject, grind #5
Broken, test #3
Reject, grind #4
Reject, grind #4
Reject, grind #5
Reject, grind #5
List, test #3
Reject, grind #5
Broken, test #3
Fifth
Reject, grind #4
Lost, test #5
_______
—
_______
1 16/32
Remarks
1 16/32
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
Variation
Second to second
Second to third
Second to fourth
Second to fifth
Second to reject
Third to third
Third to fourth
Third to fifth
Third to reject
Fourth to fourth
Fourth to fifth
Fourth to reject
Fifth to fifth
Fifth to reject
Percent
0
0
0
0
0
0
50
0
50
0
50
50
22
78
Remarks
•
•
•
•
•
•
•Previous grinding had reduced the bits to all below the second
size.
•*0f the 50% of the fourth bits going to reject, 50% of these
were rejected by virtue of being too small to sharpen, 50% were
lost in the previous underground test.
44
Mechanical Grind #6 *
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4_1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
Height After
Sharpening
—
—
_______
—
— — —
—
___
— —
—
_
— — —
—
—
—
_
_
___—__
—
—
—
—
—
_______
— — —
Remarks
Lost, test #7
Reject, grind #6
Lost, test #6
Reject, grind #5
Reject, grind #5
Reject, grind #6
Reject, grind #5
Reject, grind #5
Reject, grind #5
Broken, test #3
Reject, grind #4
Reject, grind #4
Reject, grind #5
Reject, grind #5
Lost, test #3
Reject, grind #5
Broken, test #3
Reject, grind $6
Reject, grind #4
Lost, test #5
*0nly four bits remained following the previous grinding (#5) and
these were rejected as being too small to sharpen when they were
returned for grind #6. The above tabulation is merely labelled
as Mechanical Grind #6 in order to provide space to include a form
giving the information resulting from the last of the underground
tests.
CHAPTER IX
HOT MILLING
The hot milling process for the reconditioning of rock
drill bits is not new.
It has been employed by a few mines for
years and in the past decade it has been widely adopted, as its
advantages have become better known.
Because of the extensive
commercial development in England and Canada of machines to operate
on this principle, general acceptance has been largely in the .
British possessions and until recently has been chiefly in the
field of conventional steel.
In the past two years there has been
a definite trend toward hot milling of detachable bits in Canada
but only in the past year or so has any considerable attempt been
made to build a special machine for this type of work. Generally
a machine designed for conventional steel has been used and special holders employed to manipulate the bit.
As early as 1934 at least one operator in the United States
had adopted hot milling to conventional steel with a saving in
resharpening costs. Several other operators have taken it up but
there has been no wide spread adoption of the method in this country
by users of conventional steel. This may be partly explained by
the fact that until recently no American manufacturer produced
this equipment and operators have been obliged to build their own
hot millers or import them.
Several years ago a few machines were
built in Seattle, Washington and operated in some mines in the
46
northwest but, for reasons not generally known, the effort was a
abondoned.
General mechanics of the process. Hot milling performs
the function of redressing the bit, at a suitable forging temperature,/the removal of metal from the flutes with a milling cutter
followed by a similar cut from the bit gauge. Conventional bits
are thus treated following the usual forging operation, in a sharpener, and usually at the same heat.
Removable bits are hot milled in essentially the same way,
except that the die forging operation is not employed to swage the
bit to approximate gauge. Normally a standard removable bit is
used of heavy body design and the removal of metal by the cutter is
somewhat analagous to the grinding method in -that cutter and grinding wheel perform the same duty and the same surfaces of the bit
are brought in contact with the cutting device.
A hot milling machine consists of a motor driven rotary
milling cutter of high quality steel suitably mounted on a frame
or base. Guides and stops confine the bit to the desired position
in relation to the cutter. The bit is milled in two main operations, which successively bring the bit wings to sharpness by fluting cuts and take off the gauge to the desired diameter by the
gauging cut.
Development trends. The several different machines for
removable bits that have evolved in the past year differ in principle chiefly in the manner in which the bit is presented to the
cutters or cutter. At present there appear to be two schools of
Resultant of
Guttling Force
Direction of
Rotation of
Cutter
Parallel to
Bit Axis
\
/
RECEDIIB CUT
Resultant of
Cutting Force
>
Parallel to
Bit Axis
Direction of
Rotation of
\
Cutter
/
APP3QACHIHG CUT
Figure 16
48
opinion as to the most efficient and effective treatment of the
bit in the fluting cut previously described. One school favors
the "receeding cut" whereas the other school favors the "apporaching"
cut in the fluting operation that brings the wings to sharpness.
The two schemes may produce bits similar in appearance yet sereral
vital factors in speed of operation and number of regrinds obtainable are affected,
Receeding cut. The receeding cut shown in figure 16 is
subject to a component of force that tends to remove the bit from
the stud which is inserted in the threaded end and which holds
the bit against the cutter. This condition necessitates a holder
which must be expanded in the threaded hole or in some other manner
firmly grasp the bit. This receeding cut also tends to leave a
flash on the cutting edges which will break off upon use of the
bit, leaving a flat spot on the cutting edges and lead to premature dullness of the bit.
Approaching cut. In the approaching cut, the forces that
are generated during contact in cutting tend to push the bit back
on its holder.
This condition obviates the use of a special holder,
and the bit may simply be placed on a plain collet integral with
the machine and after milling, removed without the extra operations of locking and unlocking the holder.
The advantages of
the approaching cut in the simplicity are thus self-evident,
The advantages of this holder are somewhat nullified when one
commences the gauging operation. In this operation when the bit
_ttraato*qtfl_Ba_&_j» A>. v _\i„
FLsMBh Accuntulates
Ji~k*_Lj___ii_K__J_.*iJ_-*.
Flash _uscu__ilates
APPROACHING CUT
RECEDING CUT
Flgt-r« 17
*; J _
,__
50
and holder are not locked, there is a tendency for the bit to
spin on the holder which leads to a less satisfactory gauging.
Still further, the approaching cut is less satisfactory
than the receeding cut in respect to the flash left on the bit.
Yihereas the flash left after the receeding cut appears on the
cutting edges of the bit and is broken off in drilling, the slight
dullness resulting from this is not so serious as the drawback
presented by the flash resulting from the approaching cut. In
this last mentioned cut, the flash appears between the flutes
and at the junction of the flutes and skirt of the bit. With
each sharpening, this flash grows and eventually reaches such a
magnitude as to restrict the free flow of cuttings from the drill
hole.
Figure 17 shows where flash appears in each of the types of
cuts.
Gauging operation with single cutter. The gauging operation is performed by rotating the bit still hot, against a
rotary milling cutter. Further divergence of principle is encountered here, the second and last main operation.
The singel
cutter shown in figure 18 employs the same cutter for fluting
and gauging whereas the double cutter scheme, figure 18 uses separate cutters for each of these
.two steps. Machines for con-
ventional steel have long employed the single cutter and little
additional advantage is seen through the addition of a separate
gauging cutter for this particular undertaking.
The different
handling characteristics of the removable bits evince other possibilities for the gauge cut and upon these factors are based
5r
&
1-f
POBsible Arrangement
Using Extra Cutter
For Gauging
r.
i.
v.
Gauging Position of
Bit on ride of
Double Duty Single
Cutter
Figure 18
52
The deviations in design.
The manually operated holder men-
tioned in connection with the receeding cut, is manipulated in
much the same way as a conventional drill piece, therefore disciples of this school are the priciple advocates of the single cutter.
Double cutter. The double cutter scheme may or may not be
used where either type of fluting cut is used. There appear to
be advantages -rath both types of these gauging possibilities and
in general it may be said that compactness and low first cost
favor the double duty single cutter while production speed may
be greater with the two cutters.
CHAPTER X
HOT MILLING AT A STANDARD PLANT
The writer was afforded the opportunity of studying the
hot milling process for reconditioning bits at a custom plant
in Butte, Montana.
This plant utilizes a regulation single cutter hot miller
and practices the receding cut, the mechanics of which have been
previously described.
Figure 19 shows the set up of the hot milling machine, the
specifications of which are as followsr
Maximum bit size handled
Horsepower —
3 l/2 inches
— —
Weight in pounds — — — —
—
1750
Cutter speed
Mounting of motor
5
3500
—
—
Drive connection —
—
Base type
— Mult. "V" belt
Cutter diameter in inches —
10
Peripheral speed in ft./min. —
8820
Over all dimensions
Length
50 3/4 inches
Width
35 l/2 inches
Height
52 2/3 inches
I
54
Figure 19
i A . __!_ *_*-..-I-A-. *-_, W __V _ -_**..*— *_, _. . -^ J , i. j.,
55
Bit sorting. The bits are brought to the plant and here
sorted for gauge and height.
This work is done in the afternoon
the bits being places on the work bench near the furnace following sorting.
Sorting consists of handling each bit individually,
and measuring it with a pocket rule.
Heating.
Thr morning following sorting, the bits are heat-
ed prior to milling.
The furnace is a semi-muffle type lined
with a refractory and using natural gas for fuel. The burning of
natural gas promotes a reducing atmosphere which helps to hold
scaling of the bit due to oxidation to a minimum.
As the bits are taken from the bench, they are placed at
the front of the furnace and gradually moved to the back of the
furnace as the bits at the rear of the furnace are removed for
sharpening. This serves to heat the bits gently and eliminates
strains resulting from too rapid heating.
As each bit reaches the rear of the furnace, it is at the
correct temperature for milling (1900 degrees F.) and is then
removed.
Milling. Each bit is removed from the furnace by the furnace operator using long steel tongs.
The bit is placed temporarily on the bit locating stand
from whence it is picked up by the bit holder or bit collet.
This holder is twenty inches long and equipped with a movable
jaw similar to that previously described in the section given
over to mechanical grinding. A wheel on the rear of the holder
56
is tightened to force a pin into the jaw and thus spread it,
thereby gripping the bit firmly.
The bit holder is then placed in the saddle of the carriage located facing the milling cutter.
This carriage is oper-
ated to and fro by compressed air thus forcing the bit against
the milling wheel. The carriage is adjusted by a screw mechanism which moves the positions of the carriage stops closer to or
farther from the cutter, depending upon whether high or short
bits are being milled.
from the bit.
This causes a definite cut to be taken
The cut taken depends upon the dullness and height
of the bit. As the bit face comes in contact with the milling
wheel, metal is cut from the face. As each section between two
wings of the bit face is sharpened, the bit holder is rotated
ninety degrees and another quadrant of the bit is sharpened.
Gauging operation. After all cutting edges are sharpened,
the bit is held against the side of the cutter to gauge the bit.
As bits of equal gauge are milled at one time, the operation consists of moving the stand in tov/ards the milling wheel by a screw
mechanism until it has reached the required position, as shown
on a scale located just below the gauging stand and which shows
the proper position of the stop corresponding to different gauge
sizes of standard bits.
Following the setting of the gauging platform at the
correct position, the bit is placed on the stand and the bit
57
holder is rotated by hand so that the direction of travel of the
bit is against that of the cutter. This brings the four reaming
surfaces in contact with the cutter thereby truing the reaming
surfaces of the bit. Then providing the bit is the center hole
type, it is placed head on against a punch operated by compressed air, and the water hole, which was partially closed by metal
during milling is cleared.
Bit sharpening by this method is very rapid.
The time
varies from twenty seconds for a side hole bit to thirty seconds
for a center hole bit.
• v
x
< • i
!
»»
*
* -
tj
•
'
%
_ t t _ J . J » - 1 — _ » _ * — * . . - _ • J,.«>»-.<•<.v.» ».. -^'J _ .. _ >
59
Test #1
Gauge
Before
Bit No. Drilling
Gauge
Hei ght
After
Before
Drilling Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-25-3
5-4
5-5
28/32
28/32
28/32
28/32
28/32
24/32
24/32
24/32
24/32
28/32
20/32
19/32
20/32
20/32
20/32
17/32
18/32
17/32
18/32
16/32
Bit Gauge
No. Bits Used
In Test
Second
Third
Fourth
Fifth
Total
30/32
30/32
30/32
28/32
30/32
28/32
22/32
24/32
24/32
28/32
24/32
22/32
24/32
22/32
26/32
22/32
22/32
18/32
20/32
22/32
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling Remarks
28/32
28/32
26/32
26/32
26/32
24/32
24/32
22/32
24/32
22/32
18/32
18/32
20/32
20/32
20/32
16/32
16/32
14/32
16/32
16/32
Total Distance
Drilled Inches
24/32
24/32
24/32
22/32
22/32
20/32
18/32
16/32
20/32
16/32
14/32
12/32
16/32
16/32
16/32
12/32
12/32
12/32
12/32
12/32
28/32
28/32
26/32
26/32
26/32
25/32
20/32
20/32
21/32
26/32
22/32
20/32
20/32
20/32
24/32
20/32
18/32
17/32
18/32
18/32
Distance Drilling
Drilling Drilled
Speed
Time Min Per Bit
In./Min.
5
5
5
5
18
19
16
19
360
45
8
General Remarks. This test was carried out in 3137-56 stope at the
Leonard mine. The ground was quartz stringered with chalcocite
similar to that encountered in all previous tests.
j-t_Mi«t--__^_______:
60
Test #2
Gauge
Before
Bit No. Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
561
5-2
5-3
5-4
5-5
1 28/32
1 28/32
1 26/32
1 26/32
1 26/32
1 24/32
1 20/32
1 22/32
1 24/32
1 22/32
1 18/32
1 18/32
1 •20/32
1 20/32
1 22/32
1 16/32
1 18/32
1 18/32
1 18/32
1 18/32
Height
Gauge
Before
After
Drilling Drilling
1 28/32
1 28/32
1 26/32
1 24/32
1 24/32
1 24/32
1 20/32
1 20/32
1 20/32
1 22/32
1 20/32
1 18/32
1 20/32
1 20/32
1 22/32
1 16/32
1 16/32
1 16/32
1 16/32
1 18/32
* Broken, Test #2
Bit Gauge
Total
General Remarks.
1 26/32
1 26/32
1 22/32
1 24/32
1 22/32
1 24/32
1 18/32
1 18/32
1 22/32
1 18/32
1 16/32
1 16/32
1 18/32
1 20/32
1 20/32
1 16/32
1 14/32
1 14/32
1 16/32
1 14/32
1 24/32
1 20/32
1 16/32
1 16/32
1 20/32
1 20/32
1 16/32
1 16/32
1 18/32
1 16/32
1 12/32
1 12/32
1 14/32
1 16/32
1 16/32
1 12/32
1 12/32
1 12/32
1 12/32
1 12/32
1 24/32
1 24/32
1 22/32
1 24/32
1 24/32
1 24/32
1 16/32
1 18/32
1 20/32
1 20/32
1 20/32
1 16/32
1 18/32
1 16/32
1 20/32
1 16/32
1 14/32
1 14/32
1 14/32
1 16/32
Remarks
Broken*
**
** Broken, Test #2
No. Bits Used
In Test
Second
Third
Fourth
Fifth
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
Total Distance
Drilled Inches
Distance Drilling
Drilling Drilled
Speed
Time Min Per Bit
In./tlin.
5
5
5
5
19
17
19
19
365
67.6
5.4
This test was performed following the first hot
milling operation. Drilling was done in 3137-56 stope at the Leonard
mine, The ground was similar to that encountered in proceeding tests.
61
Test #3
Gauge
Before
Bit No. Drilling
Gauge
Height
After
Before
Drilling Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4-5
5-1
5-2
5-3
5-4
5-5
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
24/32
24/32
22/32
22/32
22/32
22/32
16/32
16/32
22/32
18/32
16/32
16/32
18/32
16/32
20/32
24/32
24/32
20/32
20/32
22/32
20/32
14/32
16/32
18/32
18/32
16/32
14/32
18/32
16/32
20/32
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
22/32
22/32
20/32
20/32
20/32
20/32
14/32
16/32
18/32
18/32
16/32
14/32
12/32
14/32
18/32
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
18/32
18/32
16/32
12/32
12/32
14/32
10/32
12/32
14/32
12/32
10/32
8/32
8/32
10/32
14/32
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Remarks
22/32
22/32
20/32
20/32
20/32
20/32
14/32
16/32
16/32
16/32
16/32
12/32
14/32
14/32
18/32
*
•
•
•
•
•Reject, grind #2
Bit Gauge
Second
Third
Fourth
Fifth
Total
No. Bit s Used Total Distance
In Test
Drilled Inches
Distance
DrillinLg Drilled
Time Min Per Bit
0
0
2
6
18
19
7
19
283
19.5
Drilling
Speed
In ./Min,
14.5
General Remarks. This test was carried out following the second
hot milling of the bits. Drilling was done in 3137-56 stope at the
Leonard mine. Conditions were similar to those in preceeding tests.
No second bits were used because previous sharpening had reduced the
bits to such a size that no seconds were available.
62
Test #4
Bit No,
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge
Before
Drilling
Height
Before
Drilling
Gauge
After
Drilling
Length of
Cutting
Edge
After
Drilling
Height
After
Drilling
22/32
22/32
22/32
20/32
20/32
20/32
18/32
18/32
18/32
16/32
18/32
16/32
20/32
18/32
18/32
18/32
18/32
18/32
16/32
16/32
14/32
14/32
14/32
12/32
16/32
16/32
14/32
16/32
16/32
14/32
1 16/32
1 18/32
1 18/32
1 14/32
1 14/32
1 18/32
1 14/32
1 16/32
1 16/32
10/32
12/32
12/32
12/32
12/32
14/32
1 18/32
1 16/32
1 16/32
1 12/32
1 16/32
Remarks
_______
**
_______
_______
_______
**
**
**
• Reject, mill #3
••Reject, mill #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
No. Bits Used
In Test
Total Distance
Drilled Inches
Distance
Drilling Drilled
Time Min Per Bit
Drilling
Speed
In/Min.
0
0
19
19
0
0
6
4
7.6
25
after
General Remarks. This test was performed/the third hot milling.
The test was carried out in 3137-56 stope at the Leonard mine under
conditions similar to those in preceeding tests. No seconds or
third bits were used because previous milling had reduced^ the bit
sizes to such an extent that these two sizes were not available.
Total
190
63
Test #5
Gauge
Before
Bit No. Drilling
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
462
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
1
1
1
1
1
1
18/32
18/32
18/32
18/32
18/32
16/32
Height
Before
Drilling
Gauge
After
Drilling
1
1
1
1
1
1
1
1
1
1
1
1
16/32
14/32
12/32
14/32
16/32
14/32
Second
Third
Fourth
Fifth
Total
16/32
14/32
16/32
14/32
16/32
16/32
14/32
12/32
10/32
10/32
IE/32
12/32
________
1 16/32
1 12/32
1 16/32
1 14/32
* Reject, hot mill #2
••Reject, hot mill #3
Bit Gauge
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
No. Bits Used
In Test
1 16/32
1 12/32
1
1
1
1
1
1
14/32
12/32
10/32
10/32
14/32
12/32
Remarks
Fourth
Fourth
Fourth
Fourth
Fourth
Fifth
_______
He*
_______
_______
_______
***#
**
£$
1 14/32
Fifth
_______
*
_______
*
•** Reject, hot mill #4
****L.osir, test #5
Total Distance
Drilled Inches
Distance
Drilling Drilled
Time Min Per Bit
0
0
5
7
Drilling
Speed
In./l/Iin.
0
0
18
19
223
26.2
8.5
General Remarks. This test was performed following the fourth hot
milling
The test was carried out in 3137-56 stope at the Leonard
mine with ground similar to preceeding tests. No seconds or third
bits were used because previous milling had reduced the bit sizes
to such an extent- that these two sizes were not available.
CHAPTER Xll
BIT RECONDITIONING BY HOT MILLING
The following section of the report contains those tables
pertinent to the sharpening of the bits by hot milling.
As the set of bits was dulled it was returned to the shop
to be sharpened.
Following sharpening the bits were again mea-
sured previous to use in a following test.
Strictly speaking, bit sizes are as followss
Starter-2",
Second-1 7/8", Third-1 3/4", Fourth-1 5/8", Fifth-1 l/2". However, because of the overdrilling and the slight enlargment of the
hole thereby, it is possible for a hole to be drilled without this
hard and fast rule for changing bits.
For this reason any bit
which varied by not more than one-sixteenth inch minus from its
regular size was still classed as that size.
Table #2 is a recapitulation of bit sizes following each
mill.
It gives the percentage of bits which will yield another
service at the same gauge size, and also, the percentages of bits
which moved down one or more sizes.
Hot Mill #1
Bit No.
Gauge After
Sharpening
Height After
Sharpening
Remark!
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Second
Second
Second
Second
Second
Third
Fourth
Third
Third
Third
Fourth
Fourth
Fourth
Fourth
Third
Fifth
Fifth
Fifth
Fifth
Fifth
28/32
28/32
26/32
26/32
26/32
24/32
20/32
22/32
24/32
22/32
18/32
18/32
20/32
20/32
22/32
16/32
18/32
18/32
18/32
18/32
28/32
28/32
26/32
24/32
24/32
24/32
20/32
20/32
20/32
22/32
20/32
18/32
20/32
20/32
22/32
16/32
16/32
16/32
16/32
16/32
Table #2
Bit Gauge
Seconds
Thirds
Fourth
Fifth
Variation
Second to Second
Second to Third
Second to Fourth
Second to Fifth
Second to Reject
Third to Third
Third to Fourth
Third to Fifth
Third to Reject
Fourth to Fourth
Fourth to Fifth
Fourth to Reject
Fifth to Fifth
Fifth to Reject
Percent
100
0
0
0
0
80
20
0
0
80
20
0
100
0
Remarl!
Hot Mill #2
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
Gauge After
Sharpening
Heis-ht After
Sharpeining
Remark
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Third
Third
Third
Third
Third
Third
Fifth
Fifth
Third
Fourth
Fifth
Fifth
Fourth
Fifth
Fourth
24/32
24/32
22/32
22/32
22/32
22/32
16/32
16/32
22/32
18/32
16/32
16/32
18/32
16/32
20/32
24/32
24/32
20/32
20/32
22/32
20/32
14/32
16/32
18/32
18/32
16/32
14/32
18/32
16/32
20/32
_____—
___
_
_______
«*
•
•
-__-_-_
*
*Bits reject by mill operator as being too small for machine to
handle•
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
Variation
Second to Second
Second to Third
Second to Fourth
Second to Fifth
Second to Reject
Third to Third
Third to Fourth
Third to Fifth
Third to Reject
Fourth to Fourth
Fourth to Fifth
Fourth to Reject
Fifth to Fifth
Fifth to Reject
Percent
0
100
0
0
0
50
25
25
0
20
80
0
0
100
Remarks
67
Hot Mill #3
Table #1
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
Gauge After
Sharpening
Height After
Sharpening
Remark.
1
1
1
1
1
1
1
1
1
1
1
1
Third
Third
Third
Fourth
Fourth
Fourth
22/32
22/32
22/32
20/32
20/32
20/32
18/32
18/32
18/32
16/32
18/32
16/32
_______
*•
1 16/32
1 18/32
1 18/32
1 14/32
1 14/32
1 18/32
Fifth
Fourth
Fourth
—__-_
_______
— _
_______
_______
_______
**
**
**
**
4-5
5-1
5-2
5-3
5-4
1 18/32
1 16/32
5-5
»_,„.
i
__
__
Fourth
•
^
*
#
_______
#
• Reject, Mill #2
••Reject, Mill #3
Bit Gauge
Seconds
Thirds
Fourths
Fifth
Variation
Second to Second
Second to Third
Second to Fourth
Second to Fifth
Second to Reject
Third to Third
Third to Fourth
Third to Fifth
Third to Reject
Fojjrth to Fourth
Fourth to Fifth
Fourth to Reject
Fifth to Fifth
Fifth to Reject
Percent
0
0
0
0
0
43
57
0
0
67
0
33
20
80
Remarks
•
•
•
•
•
•Previous milling had reduced the bits to all below the second si2e.
68
Hot Mill #4
Table #1
Bit No.
Gauge After
Sharpening
Height After
Sharpening
Remark
2-1
2-2
2-3
2-4
2-5
3-1
3-2
1
1
1
1
1
1
1
1
3
1
1
1
Fourth
Fourth
Fourth
Fourth
Fourth
Fifth
3-3
_______
_______
1 16/32
1 12/32
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
18/32
18/32
18/32
18/32
18/32
16/32
16/32
14/32
12/32
14/32
16/32
14/32
*•
*•*
***
Fifth
••
••
**
**
1 16/32
Fifth
1 14/32
*
*
*
*
*
_______
_______
_______
_______
•Reject, mill #2
••Reject, mill #3
•••Reject, mill #4
Table #2
Bit Gauge
Seconds
Thirds
Fourths
Fifths
Variation
Percent
Second to Second
Second to Third
Second to Fourth
Second to Fifth
Second to Reject
Third to Third
Third to Fourth
Third to Fifth
Third to Reject
Fourth to Fourth
Fourth to Fifth
Fourth to Reject
Fifth £o Fifth
Fifth to Reject
0
0
0
0
0
0
100
0
0
33
50
17
0
100
Remarks
•
*
•
*
*
* Previous sharpening had reduced the bit sizes to such an extent that
no seconds were available.
69
Hot Mill #5
Table #1
Bit No.
Gauge After
Sharpening
Height After
Sharpening
2_l
—.
2_2
—
_______
2-3
_
_
2_4
—
2-5
3-1
_______
3_2
3_3
_
__
—_
3-4
_______
__-_
3_5
4-1
_
_
_
4-2
4_3
_
___
4-4
__—
_
4_5
5_1
5_2
5_3
5_4
5_5
* Reject, Hot Mill #2
** Reject, Hot Mill #3
*** Reject, Hot Mill #4
**** Reject, Hot Mill #5
***** Lost, Test #5
Remarks
****
*****
****
***•
****
*****
**
***
*****
**
**
*•
**
****
*
*
*
*
*
*
General Remarks. Eight bits renaines from the previous hot mill (#4)
and after usage they were all rejected by the operator as being too
small for his machine to handle. Therefore, hot mill # 5 is not a
sharpening but merely called as such in order to provide a form on
which to tabulate the final results and show what happened to each bit
during the entire course of tests and sharpenings.
CHAPTER Xlll
HAND GRINDING
Still another method of reconditioning detachable bits is
the hand grinding method.
This is perhaps the simplest method of sharpening.
Figure 20 shows a typical hand grinder the specifications
of which are as followst
Overall dimensions
Length in inches
48
Height in Inches
53 l/4
Width in Inches
44 l/4
Maximum Speed of Wheel in R. P. M .
1245
As in other types of sharpening, the operation consists
of first facing and later gauging.
The facing operation is performed by screwing the bit on
a short piece of drill shank and then laying the holder on a
rest with the bit facing the wheel. The holder and bit are
advanced and the bit is held against the abrasive wheel. As
each one quarter of the bit is sharpened, the bit and holder
are rotated so as to sharpen another one quarter of the bit.
After the four cutting edges are sharpened, the gauging operation is performed.
In gauging, the holder is placed in the socket provided
for it and the crank handle is rotated. Meanwhile the edgizr
wheel is advanced by a screw mechanism until contact between
the bit and wheel are made. The rotation of the bit then by
the crank mechanism serves to gauge the bit. Perhaps the greatest advantage of this method is its low first cost.
This type of sharpener is capable of sharpening fifty
bits per hour.
Figure 20
CHAPTER XIV
BIT TESTING
The following section contains the tests performed on
bits which were reconditioned by hand grinding.
Ten standard A. C M . bits of the starter size were selected from the incoming dull bit supply to the Hawkesworth plant.
These bits were handled in testing exactly as the two previous
batches, namelyj
1.
Bits measured for gauge and height,
2.
Bits sharpened.
3. Bits measured again,
4.
Bits put into use underground,
5. Above steps repeated.
73
Test #1
Gauge
Before
Bit No. Drilling
Height
Before
Drilling
Gauge
After
Drilling
Length of
Cutting
Edge
After
Drilling
1
2
3
4
5
6
7
8
9
10
2
2
2
2
2
2
2
2
2
2
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Bit Gauge
Firsts
Seconds
Total
1
1
1
1
1
1
1
1
1
1
26/32
28/32
26/32
26/32
26/32
30/32
26/32
30/32
30/32
28/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
No. Bits Used
In Test
24/32
26/32
24/32
24/32
24/32
28/32
24/32
26/32
28/32
24/32
Total Distance
Drilled Inches
18/32
22/32
20/32
20/32
22/32
22/32
18/32
22/32
26/32
22/32
Height
After
Drilling
Remarks
2
2
2
2
2
2
2
2
2
2
Second
Second
Second
Second
Second
First
Second
First
First
Second
Drilling
Time Min
3
7
O/O
0/0
O/O
2/32
2/32
2/32
0/0
O/O
2/32
0/0
Distance
Drilled
Per Bit
Drilling
Speed
In./^lin
17
18
177
22.1
8.0
General Remarks. This test was performed in 3137-56 stope at the
Leonard mine under conditions similar to those in preeeeding tests.
There were ten starter bits secured from the dull bit supply of
the Hawkesworth plant for this series of tests. The first h&nd
sharpening reduced the size of these to such an extend that of
the ten bits used in the test, seven were seconds and three were
starters,
'HS£MCJS.frk « * - ^
rti_i-fl»ngifr^-~H»r-»--irii*i
ifr'
75
Test #3
Gauge
Before
Bit No. Drilling
Height
Before
Drilling
1
2
3
4
5
6
7
8
9
10
1
1
1
2
1 16/32
1 20/32
1 16/32
1 16/32
1 16/32
1 20/32
1 16/32
1 20/32
1 16/32
1 18/32
30/? 2
30/32
30/32
0/0
> o/o
Gauge
After
Drilling
Length of
Cutting
Edge
Height
After
After
Drilling
Drilling
Remarks
*
•
*
*
*
*
2 0/0
*
I 0/0
*
•Grind #3 had reduced the size of the bits to such an extent that
no further use of these bits was possible. The above table therefore does not represent a drilling test but is merely labeled as
such in order to provide a form on which to tabulate the data.
CHAPTER XV
SHARPENING BY HAND GRINDING
^ e following table contains those tables pertinent to
the sharpening of the bits by hand grinding.
The ten dull start-
were obtained and sharpened once previous to drilling. The
bits were then used underground in each test and sharpened after
each test. By virtue of the fact that the bits were dull when
obtained, Table #1 shows the sizes of the bits before they were
subjected to use.
77
BIT SIZES PREVIOUS TO FIRST HAND GRIMD*
Table #1
R..
0#
I
Z
I
*
5
°
b
'
l8
10
Maximum
Gau e
S
Length of
Cutting
Edge
Maximum
Height
Remarks
1 30/32
0/0
1 30/32
1 30/32
1 30/32
2 0/0
2 0/0
2 0/0
1 26/32
1 28/52
1 28/32
1 26/32
1 24/32
1 26/32
1 24/32
1 28/32
2 2/32
2 2/32
2 4/32
2 4/32
2 2/32
2 4/32
2 2/32
2 2/32
First
First
First
First
First
First
First
First
1 28/32
2 4/32
First
2
2
°/°
tfthe Itrtl r P f S e n t t h e Fmoelalsouwrie * e *th
t s taken on the bits previous
were out S o f ^ ^
»
g
* " r a t hand grind the bits
Follo
Iharn^ K \
T*™ *** dnlled'
^ E testing the bits were
sharpened by hand grinding. Both testing and sharpening followed
the same pattern as practiced on the bits used in th7hot milling
S
and mechanical grinding sections of the report.
Hand Grind #1
Table #1
Bit No,
1
2
3
4
5
6
7
8
9
10
Gauge After
Sharpening
1 26/52
1 27/32
1 26/32
1 26/32
1 26/32
1 30/32
1 26/32
1 30/32
1 30/32
1 28/32
Height After
Sharpening
2/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
2/32
Remarks
Second
Second
Second
Second
Second
First
Second
First
First
Second
Table #2
Bit Gauge
Variation
First
First to First
First to Second
Percent
70$£
Remarks
*
•
•Previous to this sharpening all of the bits were of the first
or starter size. This sharpening reduced seven of the bits to
seconds while three remained firsts. As these are the onlj two
sizes of bits resulting from this grind there are no further
tabulations to be entered under Table # 2 .
79
Hand Grind #2
Table #1
Bit No.
Gauge After
Sharpening
Height After
Sharpening
Remark
1
2
3
4
5
6
7
8
9
10
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
Fourth
Third
Third
Third
Third
Second
Fourth
Third
Third
Third
20/32
24/32
22/32
22/32
22/32
26/32
20/32
24/32
24/32
22/32
2/32
0/0
0/0
_/32
0/0
0/0
0/0
0/0
2/32
0/0
Table #2 *
Bit Gauge
Firsts
Variation
First to First
First to Second
First to Third
First to Fourth
First to Fifth
First to Reject
Second to Second
Second to Third
Second to Fourth
Second to Fifth
Second to Reject
Percent
Remarks
0
33
67
0
0
0
0
71
29
0
0
•The above table represents the bit sizes resulting from the
first hand grind. As yet none of the bits have reached the third,
fourth, or fifth sizes.
8Q
Regrind j fc
Table #1
Bit No.
1
2
3
4
5
6
7
8
9
10
Gauge After
Sharpening
Height After
Sharpening
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
1
2
2
16/32
20/32
16/32
16/32
18/32
20/32
16/32:
20/32
16/32
18/32
30/32
30/32
30/32
0/0
O/O
0/0
30/32
0/0
O/O
Remark
Fifth
Fourth
Fifth
Fifth
Fourth
Fourth
Fifth
Fourth
Fifth
Fourth
a o/o
Table #2*
Bit Gauge
Seconds
Third
Fourth
Variation
Second to Second
Second to Third
Second to Fourth
Second to Fifth
Second to Reject
Third to Third
Third to Fourth
Third to Fifth
Third to Reject
Fourth to Fourth
Fourth to Fifth
Fourth to Reject
Percent
Remarks
0
0
100
0
0
0
57
43
0
0
100
0
*This concludes the regrinding by the hand method. Yftiile no bits
had as yet been reduced to the fifth size, still sharpening had
reduced the gauge of the bits and had not cut metal from the shoulder also. This was caused because all sharpening had been done
by reducing the gauge of the bit while not cutting enough material
from the height. This led to the production of a shoulder on
the bit which when the bits reached the fourth size, protuded past
the wings of the bit. For this reason it would be impossible to
drill with these bits and they had to be discarded.
CHAPTER XIV
CONCLUSION
Reference is made to pages 84, 85, 86, and 87. These pages
list the successive shsxrpenings the bits received until the time
each was rejected as being unfit for further sharpening.
In addition, other statistics are listed which provide
the basis for a comparison of the various methods of reconditioning detachable bits.
It is seen that mechanical grinding gave the most satisfactory results in that of the twenty bits sharpened by this
method, nineteen were reground once, seventeen were reground
twice, seventeen were reground three times, thirteen were reground four times, and four were reground five times before the
set was unfit for use.
Hot milling is secondary in that of the twenty bits sharpened by this method, twenty were reground once, fifteen were reground twice, ten were reground three times, seven were sharpened
four times before the set was unfit for use.
Hand grinding ranked last because of the ten bits sharpened by this method, ten were reground once, ten were reground
twice, and ten were reground three times before the set was unfit for further use.
Figure 24 shows that mechanical grinding is also superior
to both of the other two methods in that the total number of
82
regrinds for this method for the set of bits is seventy as against
fifty three for hot milling and thirty for hand grinding.
In addition, the set of bits mechanically ground drilled
2687 inches before the lot was worthless as against 1421 for
hot milling and 350 for hand grinding.
Drilling speeds also show a further advantage for mechanically ground bits in that the average drilling speeds for the
entire test were 9,96 inches per minute for mechanically ground
bits, 8,80 inches per ninute for hot milling, and 7.60 inches per
minute for hand ground bits.
Further advantages for mechanically grinding are apparent when
one sees the process in proper operation. Among these are:
Much of the work is controlled automatically and poor results
due to the human equation are somewhat eliminated.
Careful
sorting is practiced for height and gauge. There are 42 different
heights into which bits are sorted.
By this method only
a light cut is taken, thereby prolonging the life of the abrasive
wheel and increasing the number of regrinds per bit.
Hot milling on the other hand has two main advantages.
In the first place, the sharpening of bits by this method
is very rapid. A bit nay be sharpened in from 20 to 30
seconds depending u on whether it is of the side hole or center
hole type.
Also, the milling cutter is very long lasting. Records
show from 40,000 to 60,300 bits sharpened before the cutter need
83
be reconditioned.
Among the disadvantages of this method is first, the two
heatings to which a bit nust be subjected, one for sharpening and
one for tempering.
This extra heating needed for milling causes
the bit to scale excessively which is particularly not desireable on the threads of a bit which in the manufacture of the bit
in the first place, are rachined to a very close degree.
In milling, the water hole is partially filled with metal
and this is not entirely cleared.
This coupled with the fact that
a flash is left on the cutting edges and thus not permitting a
sharp surface to chip the ground may be factors which caused the
er drilling rate.
slow-
The first item hindering efficient removal of
cuttings from the drill hole by restricting the flow of vrater, and
the second producing the slightly dull cutting edges.
The reduced number of regrinds is caused by the heavy cut
taken from the bit.
The practice seers to be to set the miller
for the shortest bit of a series and mill others to this
height.
This causes the taller bits of this series to suffer at
the expense of the shorter bits.
Hand grinding on the other hand has the advantage of being
a very simple process with a low initial cost. However it is a
relatively slow process.
Perhaps its greatest fault lies in the excessive cut from the
gauge.
This is demonstrated by the fact that a bit was reduced fully
one gauge size with each sharpening.
84
MECHANICAL GRINDING
NUMBER OF SEARPENINGS
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
#0
#1
#2
#3
#4
^6
#6
2
2
2
2
2
3
3
3
3
5
4
4
4
4
4
5.
5
5
5
5
2
2
2
2
2
3
4
4
5
B
4
4
4
4
4
5
5
5
5
5
2
3
5
2
2
4
4
4
5
2
3
3
3
4
4
5
4
5
2
3
4
3
5
5
5
5
5
5
4
L
R
R
5
R
R
R
L
R
5
5
5
4
L
5
B
5
5
5
5
5
5
5
R
R
5
5
R
R
5
5
R
5
5
5
5
R
L
5
R
#Q
#1
#2
#3
#4
#5
#6
R
Sharpening #0 represents initial gauge of bit previous to testing.
Numbers in each sharpening column represent gauge size to which
bit advanced following sharpening.
In each sharpening column, the point at which R, L, or B occurs
indicates that point at which the bit was rejected, lost or broken.
Figure 21
HOT MILLING
NUMBER OF SHARPENINGS
Bit No.
2-1
2-2
2-3
2-4
2-5
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1
5-2
5-3
5-4
5-5
#e
#1
#2
#3
1*
#5
2
2
2
2
2
3
3
3
3
3
4
4
4
4
3
5
5
5
5
5
2
2
2
2
2
3
4
3
3
3
4
4
4
4
3
5
5
5
5
5
3
3
3
3
3
3
5
5
4
4
4
4
4
5
R
R
R
R
R
R
4
5
5
4
5
4
R
R
R
E
R
3
3
3
4
4
4
R
5
4
4
R
R
R
R
4
R
R
5
R
5
R
#G
#1
#2
#4
#5
5
#3
Sharpening #0 represents initial gauge of bit previous to testing. Numbers in each sharpening column represent gauge size to
which bit advanced following that sharpening.
In each sharpening column, the point at which Roccurs indicates
that point at which the bit was declared unfit for further use
and hence rejected.
Figure 22
86
EAITD GRINDING
NF'BEP. OF SHARPENING
Bit No.
1
2
3
4
5
6
7
8
9
10
#0
1
1
1
I
I
1
1
1
1
1
#1
2
2
2
2
2
I
2
1
1
2
#2
4
3
3
3
3
2
4
3
3
3
#3 #4
5,R
4.3
5,R
5,R
4,R
#o
#1
#2
#3
#5
#6
#5
#5
4,?-
5,R
4,R
5,R
4,R
#4
Sharpening $0 represents i n i t i a l gauge of b i t previous to t e s t i n g ,
Numbers in each sharpening column represent gauge size to which
b i t advanced following sharpening.
All b i t s had to be r e j e c t e d following sharpening # 3 , hence the
double entry in t h a t column.
Figure 23
FINAL COMPitrtiG-N OF SHARP-SIAG AND IWI_i-Ii*G EFFICIENCIES
il_ JH.1KICA.L
G I..A>xiG
0
22
17
15
ii
70
2687
9-96
HOT M I L L I E
o
20
16
12
5
53
14.21
fl.fln
30
0
0
n
n
30
HfiO
A
B
c
P
—i
F
H..ID
G?J:;LIIC
„—Somber of regrinds for bits with initial gauge of
B—ifuober of regrinds for "bits Tilth initial gauge of
C—dumber of regirnda for bits with initial gauge of
D~2iumber of regrinds for bits with initial gauge of
&--in_raber of regrinds for bits with initial gauge of
F—Total number of regrinds for entire set of bits.
G—Total inches drilled per set of bits.
H—average drilling speed for entire test, in inches
0
H
starter sise,
second size,
third size,
fourth size.
fifth size.
per minute.
88
SECTION 111
CHAPTER 1
A COMPARISON OF ROCK DRILL LUBRICATION OILS
Since the rock drilling equipment of a mine represents an
investment of a large sum of money, and as the life of such equipment may be prolonged by efficient lubrication, a study of eight
different oils was undertaken.
Part one of the report deals with moisture resistance tests
which were run at the Central Drill Shop of the Anaconda Copper
Mining Company from March 6 through March 10, 1941, using eight
different oil samples submitted by the A. C M . Mechanical Dept,
The test were made as followst
Four drifter machines were taken apart, wiped dry and
assembled.
The rubber gasket was removed from the water tubes in
each machine which allowed the water mix with the drilling air
and reach all parts of the machine.
The machine was mounted on
the repair stand, a shank put in the chuck and two hundred cubic
centimeters of oil were put in the air inlet of the machine and
the drill operated for one minute to allow the oil to reach all
parts.
The water was then turned on and the drill operated an
additional fourteen minutes, making fifteen minutes of continuous
operation. At the end of the test the hoses were disconnected,
the shank removed from the chuck and the machine was allowed to
stand approximately forty-eight hours, when it was taken apart
89
and each piece inspected for oil film and rust. All parts were
then wiped dry and the drill assembled for the next test.
The oils tested were designated as followst
Sample #1
Sample #2
Sample #3
Sample #4
Sample #5
Sample #6
Sample #7
Sample #8
For business reasons it was necessary to conceal the
names of the oils and they v.-ere designated as above. This section of the report is merely presented to show a satisfactory
scheme for oil testing.
The tables on the following pages show the relative amount
of oil film and rust on each part when the drills wereinspected.
90.
OIL FILM
NAME OF PART
OIL NO. 1
OIL NO. 2:
Front Head (Back End)
Front End (Front)
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls :
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Center)
Cylinder (Back)
Light
Light
Light
None
Very Light
Very Light
Medium
Medium
Medium
Medium
Medium
Medium
Very Light
Very Light
None
Very Light
None
Very Light
Heavy
Medium
Medium
Very Light
Light
Light
Medium
Medium
Light
Medium
Light
Medium
Light
Light
Medium
Light
Light
Medium
NAME OF PART
OIL NO. 3
OIL NO. 4
Front Head (Back End)
Front Head (Front)
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Center)
Cylinder (Back
Heavy
Medium
Medium
Very Light
Light
Light
Medium
Medium
Medium to Heavy
Medium
Medium
Light
Light
Light
Medium
Medium
Light
Medium
Heavy
Medium
Heavy to Medium
Very Light
Light
Light
Medium
Medium
Light
Medium
Medium
Light
Light
Light
Medium
Medium
Light
Medium
91
NAME OF PART
OIL NO 5
OIL NO. 6
Front Head (Back End)
Front Head (Front)
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Back)
Cylinder (Center)
Medium
Light
Light
None
Light
Light
Medium
Medium
Light
Medium
Medium
Medium
Light
Light
Light
Light
Medium
Light
Heavy
Medium
Heavy
Light
Light
Medium
Medium
Medium
Light
Medium
Medium
Medium
Light
Light
Medium
Light
Medium
Light
NAME OF PART
OIL NO. 7
OIL NO. 8
Front Head (Back End)
Front Head (Front)
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Center)
Cylinder (Back)
Heavy
Light
Medium
Light
Light
Light
Medium
Light
Light
Medium
Light
Light
Light
Light
Medium
Light
Light
Medium
Heavy
Light
Medium
Light
Light
Light
Medium
Light
Light
Medium
Light
Light
Very Light
None
Light
Very Light
Very Light
Medium
92
AI'OUNT OF RUST
NAME OF PART
OIL NO. 1
OIL ro. 2
Front Head
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Center)
Cylinder (Back)
Few Spots on Front
Few Spots on Splines
Few Spots on Splines
Several Spots
Few Spots
heavy Rust
Feavy Kust on Splines
Heavy Rust
Few Spots in Ports
Few Spots
Few Spots
Several Heavy Spots
Spots in All Splines
Very Few Spots
None
heavy RustHeavy Rust
One spot on Front
Few Spots on Splines
Few Spots on Splines
Very Few Spots
One Small Spot
Several Small Spots
Few Spots on Splines
Spots on 3 Pawls
Few Spots in Ports
Several Spots
Few Spots
Several Spots
Spots on Splines
None
Several Spots
Heavy Near Exhaust
Fev: Spots
HAKE OF PART
OIL NO. 3
OIL NO. 4
Front Head
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Center)
Cylinder (Back)
Few Spots on Bushing
Few Spots on Splines
Heavy Spots
Few Small Spots
Few Heavy Spots
Very Few Spots
Spots on Splines
Spots on 3 Pawls
Few Spots on Front
Few Small and 3 Heavy
Few Spots
Several Heavy Spots
Few Small Spots
Tone
Hone
Tew Spots
Few Small Spots
Small Spots on Ends
Few Spots on Splines
Several Spots
Fev/ Heavy Spots
Fev/ Small Spots
Several Spots
Spots on Splines
Spots on All Pawls
Four Spots in Ports
Fev; Spots
Small Spots
Few Spots
Spots on Splines
Fev/ Spots
None
Few Spots
None
93
I'AKE OF PART
OIL NO. 5
OIL ^0. 6
Front Head
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Each Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Ring
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)Cylinder (Center)
Cylinder (Back)
1 Heavy Spot
Few Spots
Fev/ Spots
Very Few Spots
Two Small Spots
Several Small Spots
Spots on Splines
Very Little Rust
Several Spots
Few Spots
Very Few Spots
Several Small Spots
Few Spots
Hone
Fev/ Snail Spots
Few Spots
Small Spots in Ports
Fev/ on Bushing
Fev/ Spots
Fev/ Spots
Very Fev/ Spots
Three Small Spots
Fev/ Small Spots
Little Rust
Very Little Rust
Two Spots
Three Spots
Very Fev/ Spots
Very Few Spots
Very Few Spots
None
Fev/ Small Spots
Fev/ Spots
None
NAME OF PART
OIL NO. 7
OIL NO. 8
Front Head
Combination Chuck Sleeve
Chuck Bushing
Anvil Block
Back Head
Ratchet Ring
Rifle Bar
Pawls
Valve Chest
Valve Plug
Automatic Valve
Piston (Back End)
Piston (Splines)
Cylinder (Front)
Cylinder (Liner Bushing)
Cylinder (Center)
Cylinder (Back)
Several Spots
Few Spots
Few Spots
Fev/ Spots
Three Spots
Several Small Spots
Spots on Splines
Very Little Rust
Fev/ Spots
Few Spots
Very Few Heavy Spots
Fev/ Small Spots
Fev/ Spots
None
Very fev/ Spots
Few Spots
Few Spots
None
Few Spots
Few Spots
Fev/ Spots
Two Small Spots
Few Small Snots
Few Heavy Spots
Very Little Rust
Several Spots
Fev/ Spots
Several Small Spots
Few Spots
Several Spots
Few Spots
Several Small Spots
Several Small Spots
Several Small Spots
COPTER 11
UNDERGROUND TESTING FOP. CHARACTER OF OIL MIST AND LUBRICATION
OF MACHINE
General Set-uo.
Foll-v/ing the moisture resistance tests at the
Central Drill Shop the eight oils were tested underground at the
Tramway Mine. Machines used were a drifter and stoper. Eight lubricators were marked corresponding to each different oil, and the same
lubricator used to test a definite oil in both stoper and drifter
runs. Two hundred and fifty cubic centimeters of oil were poured
into the lubricator which v/ss then connected to the air line. A
fifty foot air hose led from the lubricator to the rock drill.
Before drilling twenty five cubic centimeters of the oil sample were
poured into the air hose.
Reference to the sketch included in the report will show the
general lay-out of 3405 XCN v/here the tests were conducted.
Drilling was done with both the drifter and stoper. Three
third steel holes were drilled with each machine for each oil or a
total of six holes for each of eight oils. The twenty four drifter
holes were drilled at an angle of plus one degree while the angle
of the twenty four stoper holes varied from forty to seventy five
degrees.
The proceedure followed in testing each oil was identical and
is as follows.
Previous to drillir.r the machine was taken apart, carefully
inspected and wiped dry.
:he machine was then assembled, lubricator
filled and attached -o th- air li n e .
Twenty five cubic centimeters
W
? B-^N C-° ^ K -° UV-E' ^ ~^°
[ ^rC Fy'lVVi r ^ T hfc~>V5 \EJPTTT K- £"
•r
\
X
^
u
96
of oil poured into the air hose and all hose connections to the
machine completed.
The machine was then operated until three
third steel holes had been drilled. Drilling was then stopped,
the lubricator removed from the line and carefully drained. The
amount of oil being measured and the amount of oil used in each
test was thereby obtained.
The machine was taken apart and in-
spected for the amount of oil film. Each part was carefully
wiped dry and the machine assembled for the following test.
Impinger samples were pulled at location X (See sketch).
The water pressure was 275 pounds and the air pressure 100
pounds.
The flow of water through each machine was 1.93 gallons
per minute through the drifter and 2 gallons per minute through
the stoper. All lubricators were set to permit maximum lubrication.
The data obtained from the test is listed on the following pages.
CHAPTER 111
OIL TEST VJITH DRIFTER
Test #l~Oil Sample #8
Hole
No,
1
2.
3
Drilling
Time
Minutes
Deptn
Of Hole
Inches
Drilling
Speed
In./Min.
6.65
5.81
6.13
60|60|57i-
9.1
10.4
9.4
Total 18.59
178ir
9.6
Pitch
of
Hole
C C . Oil
Used
In Test
C C . Oil
Used
Per Hour
1
1
1
166
536
Remarkst A heavy fog was noticed at the start of drilling. A slight
oil odor and a small amount of oil in the exhaust was also noticed.
The machine -.ran. cool on hole No, 1. The oil odor was more pronounced
during hole No. 2, and the machine was slightly warm at the end of
hole No, 2, The fog was heavy during hole No. 3 with very little oil
in the exhaust. The fog clears in 1,40 minutes.
Test #2—Oil Sample #7
Hole
No.
Drilling
Time
Minutes
Depth
of Hole
Inches
5.48
5,00
5.06
59
62ir
60
Total 15.54
181%
1
2
3
Drilling
Speed
In./Min.
10.8
12.5
11.9
Pitch
of
Hole
C C Oil
Used
In Test
C C Oil
Used
Per Hour
1
1
1
143
552
Remarkst The fog was heavier than that of oil No. 8. A more pronounced oil odor was noticed though not unpleasant. The machine was
cool at the end of hole No. 1. A medium amount of oil shov/ed in the
exhaust. Machine warm, fog slightly heavier, and odor stronger, for
hole No. 2, Machine cool at end of hole 3, oil odor offensive, less
oil in exhaust.
Test #3—Oil Sample #6
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
of Hole
Inches
5,25
5.31
6.14
59
53
60
16.70
172
Drilling
Speed
In./Min.
11.2
10.0
9.8
10#3
Pitch
Of
Hole
C C Oil
Used
In Test
C C Oil
Used
Per Hour
1
1
1
139
4g9
98
So^chJk^°s gaTeahe&vyfog /r mstart -
*»mach^«™»•»
Sh nS at t h e end
St
Ma«M
J
° f h ° l e N0 * U 0 i l 0 d o r -»t unpleasant' FofW C ° 0 1 a t t h e e n d ° f h ° l e N ° ' 2 * 0 i l ° d 0 r b e ° ^ unnleasSr'bushfng to"harndlAt *** ° f ^
* ° # m a C M n e ^ h<>t & r ° U n d Cylin "
Test #4—Oil Sample #5
Hole
No.
1
2
3
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./Min.
6.84
6.71
5.52
65
65
63
9.5
9.7
11.4
Total 19.07
193
10.1
Pitch
Of
Hole
C C Oil
Used
In Test
c.C. Oil
Used
Per Hour
1
1
1
75
236
Remarks:
e 7 as a h e a v
The
._,_. _•• ,, D u r i n S 5 °tl he eN S°t*&1r ttehre rSteel
'
y f °6*
machine was
Durin
the
^HTIOV
^ °5
S
remainder of the run
the machine stayed slightly warn and a faint cup grease odor was
noticed.
Test #5—Oil Sample #4
Hole
No,
1
2.
3
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./Min.
5,00
4.53
5.62
62
59
53
12.4
13.0
9.4
Total 15.15
174
11.5
Pitch
of
Hole
C.C. Oil
Used
In Test
C.C. Oil
Used
Per Hour
50
198
1
1
1
Remarks: The fog of this oil was similar to that of oil No. 8. The
machine was cool at the end of hole No. 1. The fog was very heavy
,mni».,..x odor
_j__
*
during hole No. 2 with a slichtlv
i-ghtly unpleasant
Test #6—Oil Sample #3
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./'in.
4.24
3.87
3.57
61
60
61
14.4
lb.5
17.1
11.64
182
15.6
Pitch
Of
Hole
C C . Oil
Used
In Test
C.C Oil
Used
Per Hour
1
1
1
69
356
99
Remarks: During hole No. 1 a heavy fog was apparent with a faint
cup grease odor though the odor was not unpleasant. The machine was
cool with excess oil in the exhaust. During hole No. 2 the machine
was still cool and some oil was noticed in the exhaust. At the end
of hole No. 3 the machine v/as slightly warm around the front cylinder
bushing.
Test #7—Oil Sample #2
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./Min.
3.73
4.24
3.55
54
65
57
14.5
15.3
16.1
11.52
176
15.3
Pitch
Of
Hole
C.C Oil
Used
In Test
C C . Oil
Used
Per Hour
1
1
1
67
348
Remarks: This sample gave a heavy fog. The fog also had a slightly
unpleasant odor. During hole No. 1 the machine ran cool with excess
oil in the exhaust. During hole No. 2 the machine was still cool.
During hole No. 3 the machine v/as cool, the fog heavy v/ith a slightly
offensive odor. During this run the air pump on the station was running and this may have contributed to the fog.
Test #8—Oil Sample #1
Hole
No.
Drilling
Time
Minutes
1
2
3
4.14
2.94
4.07
Total
11.15
Depth
of Hole
Inches
Drilling
Soeed
In./lin.
47
57
58
11.4
19.4
14.3
162
14.5
Pitch
Of
Hole
C C . Oil
Used
In Test
C.C. Oil
Used
Per Hour
1
1
1
79
426
Remarks: This oil has a slightly unpleasant odor. The fog was heavy
from the start. The machine ran cool on hole No. 1. Though the machine continued to run cool, the fog was slightly irritating to the
eyes and throat.
AiliNTANA -ChO-.
.o _._iUiY.
100
CHAPTER IV
LUBRICATION DATA DRIFTER
NAME OF R R T
OIL #8
0IL# 7
OIL #6
OIL #5
Drill Recip, Time
Imp. Sample Time
Front Head
Chuck Bushing
Com. Chuck Sleeve
Anvil Block
Back Head
Back Head Ports
Rifle Bar
Pawls
Ratchet Ring
Ratchet Ring Ports
Valve Chest
Automatic Valve
Valve Plug
Piston Back End
Piston Splines
Cyl. Front Bore
Cylinder Bushing
Cylinder Bore
Cyl. Counter Bore
18.59
28.00
Very Light
Very Light
Very Light
Light
Medium
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Very Heavy
Heavy
Medium
Light
Medium
Heavy
Medium
15.54
25.85
Very Light
None
Light
None
Medium
Heavy
Medium
Medium
Medium
Medium
Light
Light
Light
Very Light
Very Light
Very Light
Light
Very Light
Light
16.70
27.52
Very Light
None
Very Light
None
Light
Light
Medium
Medium
Medium
Medium
Medium
Medium
Medium
Medium
Light
Very Light
Light
Medium
Light
19.07
29.97
Very Light
None
Light
None
Medium
Heavy
Medium
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Light
Light
Light
Light
Medium
NAME OF PART
OIL #4
OIL #3
OIL #2
OIL #1
11.68
21.20
Very Light
None
Very Light
Very Light
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Light
11.52
23.55
Very Light
Very Light
Very Light
Very Light
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Very Light
Light
Medium
Medium
11.15
21.42
Very Light
Very Light
Light
Very Light
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Light
Light
Medium
Medium
Drill Recip. Time
15.15
Imp. Sample Time
23.59
Front Head
Very Light
Chuck Bushing
None
Com. Chuck Sleeve
Very Light
Anvil Block
Very Light
Back Head
Medium
Back Head Ports
Medium
Rifle Bar
Heavy
Pawls
Heavy
Ratchet Ring
Heavy
TT
Ratchet Ring Ports "eavy
Heavy
Valve Chest
Heavy
Automatic Valve
Heavy
Valve Plug
Heavy
Piston Back End
Medium
Piston Splines
Very Light
Cyl. Front Bore
Light
Cylinder Bushing
Cylinder Bore
Light
Cyl, Counter Bore
Medium
T .1
1
i
-'ediur
-'ediurr
Medium
CHAPTER V
OIL TEST 7/1TH STOPER
T e s t #9—011 Sample #8
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./Min.
7.49
3.96
5.26
58
59
56
7.3
14.9
10.6
16.71
173
10.4
Pitch
Of
Hole
C C . Oil
Used
In Test
C C . Oil
Used
Per Hour
31
111
65
65
70
Remarks: This oil gave a medium fog. The machine was hot at the end
of hole No. 1 v/ith a small amount of oil in the exhaust. At the end
of the run the machine had cooled v/ith a slight amount of oil in the
exhaust. The odor was slightly offensive.
Test #10—Oil Sample #7
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./lin.
6.56
6.29
5.68
58
56
54
8.8
8.9
9.5
18.53
168
9.1
Pitch
Of
Hole
C.C. Oil
Used
In Test
C.C. Oil
Used
Per Hour
69
75
75
97
314
Remarks: This fog was slightly heavier than oil No. 8. The odor was
slightly offensive. The machine was cool at the end of hole No. 1
with some oil in the exhaust. At the end of the run the machine was
still cool with a slight amount of oil in the exhaust.
Test #11—Oil Sample #6
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./Kin.
7.9
8.8
6.86
6.11
4.49
54
54
49
10.9
17.46
157
9.0
Pitch
Of
Hole
C C . Oil
Used
In Test
C C . Oil
Used
Per Hour
99
340
62
60
65
Remarks: The fog was slightly heavier than oil No. 7 v/ith only a
slightly offensive ordor. The machine was cool at the end of hole No. 2.
A small amount of oil in the exhaust. At the end of the run, the
machine was hot around the cylinder bushing and a trace of oil in the
exhaust.
102
T e s t # 1 2 — O i l Sample #5
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
of Hole
Inches
Drilling
Speed
In./Min.
4.95
5.68
5.16
57
39
58->-
11.5
10.4
11.3
15.79
174i-
11.1
Pitch
Of
Hole
C C Oil
Used
In T e s t
C.C. Oil
Used
Per Hour
58
60
60
67
255
Remarks: This fog was slightly heavier than oil No. 8. The machine
was warm around the cylinder bushing during hole No. 2 with some oil
in the exhaust. At the end of the run the machine was warm and no
trace of oil was found in the exhaust.
Test #13—Oil Sample #4
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./^in.
6.85
5.51
4.56
62
59
56
9.1
10.7
12.3
16.92
177
10.5
Pitch
Of
Hole
C.C. OilL
Used
In Test
C.C Oil
Used
Per Hour
47
167
46
54
51
Remarks: This fo g was slightly heavier than oil No. 8 with only a
faint oil odor. The machine v/as slightly warm at the cylinder bushing.
There was considerable oil in the exhaust. At the end of the run the
machine was hot around the cylinder bushing and there was no trace of
oil in the exhaust.
Test #14—Oil Sample #3
Hole
No.
Drilling
Time
Minutes
1
2
3
5.12
5.27
7.62
Total
18.01
Depth
Of Hole
Inches
Drilling
Speed
In./:in.
58
56
62
11.3
10.6
176
9.8
8.1
Pitch
Of
Hole
C.C. Oil
Used
In Test
C.C. Oil
Used
Per Hour
59
52
42
77
256
Remarks: This fog v/as lighter than oil Ho. 8. There v/as a slight cup
grease odor. The machine was cool at the end of hole No. 1 with con-"
siderable' oil in the exhaust. During hole No. 2 the fog increased.
The machine was warm at the end of the run with a trace of oil in the
exhaust. The fog also lessened.
103
Test #15—Oil Sample #2
Hole
Ho.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inche s
Drilling
Speed
In./fin.
5.48
5.62
4.77
63
62
59
11.5
11.0
12.4
15.87
184
11.6
Pitch
Of
Hole
C.C. O i l
Used
In Test
C C Oil
Used
Per Hour
75
284
47
49
55
Remarks: The fog v/as slightly heavier than oil No. 6 with a slightly
unpleasant odor. The machine v/as cool at the end of hole No. 1 with
some oil in the exhaust. The machine remained cool through hole No. 2
with some oil in the exhaust. At the end of the run the machine was
cool with a small amount of oil in the exhaust. The fog was heavy
and slightly offensive.
Test #16—Oil Sample #1
Hole
No.
1
2
3
Total
Drilling
Time
Minutes
Depth
Of Hole
Inches
Drilling
Speed
In./lin.
6.10
9.52
5.27
58
59
59
9.5
6.2
11.2
20.89
176
(.4
Pitch
Of
Hole
C C Oil
Used
In Test
C C Oil
Used
Per Hour
40
45
43
119
342
Remarks: The fog v/as heavier than oil No. 8 and definitely offensive
to nose and throat. The machine was cool at the end of hole No. 1
with considerable oil in the exhaust. The machine was slightly warm
at the end of hole #2 and still oil in the exhaust. During the third
hole the fog became very heavy. At the end of the run, the machine
was cool with a trace of oil in the exhaust.
104
CHAPTER VI
LUBRICATION DATA STOPER
NAME OF PBRT
OIL #8
OIL #7
OIL 46
OIL #5
Drill Recip. Time
16.71
Imp, Sample Time
26.30
Front Head
Medium
Chuck Bushing
None
Com, Chuck Sleeve
Medium
Anvil Block
None
Back Head
Heavy
Back Head Ports
Heavy
Rifle Bar
Heavy
Pawls
Heavy
Ratchet Ring
Heavy
Ratchet Ring Ports Heavy
Flapper Valve
Medium
Valve Chest
Heavy
Piston Back End
Medium
Piston Splines
None Cylinder .
Medium
Cylinder Busning
Light
18.53
28.52
Light
None
Medium
None
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Medium
Light
Light
Medium
Light
17.46
24.93
Medium
None
Medium
Light
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Eeavy
Medium
Medium
Medium
Light
15.79
22.92
Medium
None
Medium
Medium
Eeavy
Eeavy
Heavy
Heavy
Heavy
Heavy
Heavy
Eeavy
Medium
Medium
Medium
Medium
NAME OF PART
OIL #4
OIL #3*
OIL #2
OIL #1
Drill Recip. Time
Imp. Sample Time
Front Head
Chuck Bushing
Com. Chuck Sleeve
Anvil Block
Back Head
Back Head Ports
Rifle Bar
Pawls
Ratchet Ring
Ratchet Ring Ports
Flapper W i v e
Valve Chedt
Piston Back End
Piston Splines
Cylinder
Cylinder Bushing
16.92
25.96
Medium
None
Heavy
Light
Heavy
Heavy
Medium
Heavy
Heavy
Heavy
Medium
Medium
Medium
Light
Medium
Light
18.01
28.15
Medium
None
Heavy
Medium
Heavy
Heavy
Medium
Heavy
Heavy
Heavy
Heavy
Eeavy
Heavy
Medium
Medium
Medium
15.87
25.00
Medium
None
Heavy
Light
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Medium
Light
Heavy
Medium
20.89
34.10
Light
None
Light
None
Heavy
Eeavy
Medium
Heavy
Heavy
Eeavy
Heavy
Ileavy
Light
Light
Medium
Light
•Film of oil on parts resembled a carbon deposit.
105
CHAPTER Vll
SUMMARY AND CONCLUSIONS
C C . of
Oil
Test Oil Per
Sample No. Hour
Comparative Density of Mist
Odor
8
7
6
5
4
3
2
1
8
7
6
5
4
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Faint oil odor
Pronounced oil odor
Slight oil odor
Faint cup grease odor
Slight unpleasant odor
Faint cup grease odor
Slightly unpleasant
Definitely offensive
Slightly offensive
Slightly offensive
Slightly offensive
Faint oil odor
Faint oil odor
Slight cup grease odor
Slightly unpleasant
Irritating to nose
Oil
Sample
Comparative Appearance of Impinger Flasks
Lubrication
of Machine
8
7
6
5
4
3
2
1
8
7
6
5
4
3
2
1
Fairly heavy emulsion
Emulsion slightly heavier than oil 8
Slightly less emulsion than 8
Slightly less emulsion than oil 8
Emulsion same as oils 5 and 6
Slightly less emulsion than oils 4,5,6
Slightly more emulsion than oil 3
Very slight emulsion
Only slight emulsion
Less emulsion than oil 8
Approximately same as oil 7
Approximately same as oils 6, 7
Slightly more emulsion than oils 5,6,7
Approximately same as oil 4
Approximately same as oils 3, 4
Same as oils 2,3,4
Sufficient
Insufficient
Sufficient
Sufficient
Sufficient
Sufficient
Sufficient
•
Sufficient
••
Insufficient
Insufficient
Sufficient
Sufficient
Sufficient
Sufficient
••*
Sufficient
Sufficient
536
552
499
236
198
356
348
426
111
314
340
255
167
256
284
342
Hebvy
Heavier than oil 8
Heavy fog, same as oil 7
Fog heavier than 6, 7, 8
Fog same as oil 8
Heavy
Heavy to very heavy
Heavy
Medium fog
Fog slightly heavier than 8
Fog slightly heavier than 7
Fog slightly heavier than 8
Fog slightly heavier than 8
Fog heavy tc light at end run
Fog heavier than 8
Fog very heavy at end of run
Remarks
• The station pump was operating v/hich may have contributed to the fog.
••Fog caused slight headache an" irritation to nose and throat.
•••Film of oil on parts resembled carbon deposit.
106
Conclusion.
The preceeding page contains the summary of
both stoper and drifter tests.
It is seen that there is a high variation in the cubic centimeters of oil used in the various tests.
There seems to be no direct connection between the amount of
oil used and the lubrication qualities. Test #5 using 198 C.C of
oil #4 gave sufficient lubrication whereas test #2 with oil #7 used
552 C.C, of oil and gave insufficient lubrication.
This is probab-
ly due to the viscosity of the oil. In oils of low viscosity, the
major portion of the oil was blown out the exhaust with an insufficient amount clinging to the parts of the machine. The more iriscous
oils had a greater tendency to stay in the machine and form a good
oil film.
In line v/ith the odor resulting from each test, it was noted
that there v/as some sort of odor with each oil. These ranged from a
faint oil odor to a definitely offensive odor.
?i/hile the oil odor was not unpleasant, those odors noted as
offensive or unpleasant v/ere so designated because they proved irritating to the nose and throat and in some instances caused a slight
headache.
This is significant when it is realized that in each test
only three holes were drilled, and were moredrilling done, as in the
case of mining operation, the odor and unpleasant effects associated
with it might interfere seriously with the efficiency of the miners
Of all samples used, oils 6, 5, 4, 3, 2, and 1 all gave suff-
107
icient lubrication of the machine in both drifter and stoper runs.
It is safe to say then that oils 7 and 8 should be rejected here and
not considered further.
Of the remaining oils, #6 gave good emulsion in the case of
the drifter and poor emulcion in the stoper test. Oil #6 gave good
emulsion for the drifter and poor for the stoper. Oil #4 gave good
emulsion for the drifter and fair emulsion for the stoper. Oil #3
gave fair emulsion in both cases of drifter and stoper. Oil #2 gave
fair emulsion in both cases of drifter and stoper. Oil #1 gave poor
emulsion for the drifter test and fair for the stoper. The quality
of emulsion is regulated by the ability of the oil to mix with the
air and water and hence reach all parts of the machine.
On the basis of the fog, oil #6 was heavy for both stoper and
drifter test, #5 was very heavy for the drifter and heavy for the
stoper. Oil #4 was heavy for both tests. Oil #3 was heavy for drifter and medium for the stoper. Oil #2 was heavy in both cases and
oil #1 was heavy for the drifter and very heavy for the stoper.
In regard to the odor, oil #6 gave a slight oil odor on the
drifter run while the odor was offensive on the stoper run. Oil #5
gave a faint cup grease odor on the drifter test and a faint oil
odor on the stoper run. Oil #4 gave a slight unpleasant odor on the
drifter run while there was a faint oil odor on the stoper test.
Oil #3 gave a faint cup grease odor on both drifter and stoper runs.
Oil #2 was a slightly unpleasant odor in both drifter and stoper
108
tests. Oil #1 had an offensive odor on the drifter run v/hile in the
stoper test the odor v/as offensive to the nose.
In view of the above findings it seems best to recommend
either oil #5 or oil #3 on the basis of the odor as neither of these
two oils proved unpleasant.
On the basis of fog, however, oil #3 was superior to oil
#5 because of the lighter fog produced.
In respect to the emulsion produced, oil ^=5 was superior to
oil #3 and in that #5 gave a good emulsion in contrast to the fair
emulsion produced by oil #3.
In conclusion therefore we may say that either oil #3 or oil
#5 were the most satisfactory v/ith the final choice being made after
further testing to see which is more desirable, the good emulsion and
heavy fog as in the case of oil #5, or the fair emulsion and light
fog as in the case of oil #3.
109
BIBLIOGRAPHY
Mosier, McHenry, "Progress Report on Investigation of Detachable
Rock Drill Bits." U.S. Bureau of Mines, Information Circular 6877.
Berggren, Robert C , ''Hot Milling of Rock Drill Bits." Mining
Technology, Technical Publication 1215, September 1940.
Numerous Unpublished Reports of Investigations of the Engineering
Research Department of Anaconda Coppa* Mining Company.
Mr. Don Edv/in Harvey has satisfactorily completed on this
4 day of June, 1941, all requirements prescribed by the Montana
School of Mines for the degree of Master of Science in Mining
Engineering.
Graduate Committee
(Xi ^YJ^t-Owwx
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