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Патент USA US2412786

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Dec. 17, 1946.
M; 1.. TUCKER
A 2,412,786
APPARATUS FOR CENTERING SHANKS IN CASTING DIAMOND BITS
Filed Nov. 9,- 1944
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Patented Dec. 17, 1946
2,412,786
UNITED STATES PATENT OFFICE‘)
APPARATUS FOR CENTERING SHANKS IN
CASTING DIAMOND BITS
Mana L. Tucker, Detroit, Mich., assignor to‘ Chi
cago Pneumatic Tool Company, New York,
N. Y., a corporation of New Jersey
Application November 9, 1944, Serial No. 562,227
3 Claims.
(Cl. 22—5S)
I
2
This invention relates to apparatus for casting
composite diamond bits.
‘
The main object of the invention is to provide
apparatus containing a'die in which the diamonds
are properly supported for casting metal or alloy
to encompass them and having means for. accur
ately centering a bit blank over the diamonds so
that the resulting cast bit will run true during
drilling.
'
_ Aiurther object is to provide such a simplev
apparatus‘for casting diamond cutting and drill
ing bits that only very few parts are required
to be assembled to form. the mold for‘ casting,
a centering plug or stud H and a holding ‘cap I2
is passed down upon the plug and screwed upon‘
thread 13 of the bit blank until the‘ upper ‘end
of the latter engages against a radially‘extending
locating flange or projection :l 4 and also shoulder
I5 of the cap engages against the same flange
from above. At the same time the lower end is
of the holding cap rests against shoulder 11‘ on
the bit blank, the latter and the holding cap as
well as the centering plug are thus held in rigidly
assembled
relation;
.
‘
‘
‘
‘
The die or holder 18 is placed in position upon
the vacuum chamber I 9 so as to rest in the'recess
and,vafter casting, to be taken apart to‘release
2| in the upper part of said chamber. The men~
the cast‘bit.
_
.
‘
15 tioned die has an annular groove‘22 (Figs. 6 and
, Other objects and the advantages of the in
7) open to the top with‘a ‘generally concave bot
vention are set forth more fully in detail in the
following speci?cation in conjunction with the
accompanying drawing, in which:
tom 23 perforated by a plurality of holes 24 ex
tending down to the lower surface 25 of said die ‘
and at their upper extremities being adapted to .
,Fig. 1 is a vertical section of the entire appa 20 seat the cutting diamonds 26.“ ‘The vacuum
ratus with a complete cast diamond bit in place;
chamber l 9 is connected to an exhaust pump (not
Fig. 2 is a vertical section of the cast bit after
shown) by pipe 2? and the pump started so that
release from the mold and before trimming;
a partial vacuum is created in chamber L9. The
Fig. 3 is a similar view of the castbit after‘ the
diamonds are individually seated in the upper
excess cast metal has been trimmed oil;
_ ends of holes 24 so that the entire bottom ‘23
Fig. 4 is a vertical section of the bit blank alone
of the annular groove is substantially studded
before applying cast metal or attaching diamonds
thereto;
-
‘
with them, being held in place by the downward
suction through the holes 24 past said diamonds.v
The bit blank assembly previously described is
Fig. 5 is another view of the same bit blank as
39 O set upright on’ die I8 by ‘?tting a central tip or,
seen from the bottom in Fig. 4;
Fig. 6 is a'plan ‘view of the main die of the
pilot portion 28 of the centeringplug ll into a
apparatus; and
central aperture 29 in the die 25 which is con-'
Fig. '7 is a transverse section of the same die
.
- I
centric with the annular groove 22 so that the
taken along the line 1-1 in Fig. 6.
plug stands upright with its shoulder 3| resting’
Heretofore the practice of setting and casting 5:3 Ll on the die upon the annular area 32 around said
diamonds in a group to form a diamond bit has
central aperture, thus ensuring the concentricity
frequently entailed the use or more or less com
of the bit blank with the groove. The ?ask ring
plicated apparatus requiring a large outlay not
33 is also placed in position with its lower recess
only for the equipment but also for skilled labor
portion 34 ?tted upon the top 35 of the die and
to cast the bits. In some cases the bits were 40
the molten metal or alloy 36 poured into thev
made by makeshift methods and means in con
nection with which the molten metal was ?rst
cast and then mounted separately on the bit
blank with the result that all too often the metal
holding the diamonds and the bit blank did not
run concentrically.
In order to overcome these and other disad
vantages and particularly with the foregoing ob
jects in view, it is now contemplated to hold the
bit blank in true concentricity with a portion in
a die serving to support the diamonds and re
ceive the molten metal as will now be set forth
in detail.
upper concave portion 31, and ?owing down over
and encompassing the diamonds 25 and also pass
ing through anchoring holes 38 in the lower re
duced portion 39 of the bit blank. The suction
prevents the diamonds 26 from rising under the
‘buoyant force of the metal which has a greater
speci?c gravity. As soon as su?icient casting
metal has been poured, the exhaust pump is '
stopped and the molten mass is permitted to cool.
As it does, the molten metal shrinks to a very
tight ?t upon reduced portion 39 of the bit blank
and in the holes 38,‘ thereby adhering so ?rmly
Hence, referring again to the accompanying
to the bit that it is virtually integral therewith.
drawing the bit blank In (Fig. 4) is mounted on 55 As soon as the die arrangement is to be disas
"
'
2,412,786
4
sembled the following procedure may be carried
out.
- When the casting is su?cientl'y cool the die [8
and the ring 33 as well as the casting and the bit
‘ blank assembly are removed from the vacuum
chamber and the die cautiously removed from the
casting andthe ?askring, after which the latter
' is removed. Then the holding cap I2 is unscrewed
from threads IS on the bit and removed from the
centering plug II, and thereafter the latter is
withdrawn from within the bit, with said bit ap
pearing substantially as shown in Fig. 2. The cast
metal 4|, 42 is trimmed off preferably by turning
2. Apparatus for casting an accurately centered
diamond drill bit comprising a die having an an
nular recess perforated at the bottom for indi
vidually seating a plurality of diamonds and a
central aperture, means cooperating with said
die for receiving and retaining molten metal in
association therewith during-casting, means for
producing suction through" the perforations in
said annular recess past said diamonds to retain
the latter in position, a centering plug having a
body portion adapted to extend through and sup
port a bit blank in predetermined position above
the die and terminating at one end in a central
tip of reduced diameter, said central tip being
in a lathe to produce a ?nished bit as shown in
Fig. 3, wherein it is evident that the major E01‘:
tion of the cast metal 36 above the portion thereof
adapted-to ?t into the central aperture in said die
actually holding the diamonds has been out
substantially to the inside and outside diameters
the centering plug and serving as a stop for locat- '
43 and 44 of the bit blank to provide drillingclear
ing, the 'bit blank in predetermined position on
ance for the bit.
~ An example'of an alloy, suitable for use as the
casting metal 36 consists of 2 percent beryllium,
0.35 percent nickel and the remainder copper.
In drilling the holes 38 it is often found desir
able to remove the metal between the round hole ,
(which is illustrated) and the lower face of the
reduced extension 39 of the bit blank, thereby
concentric with the annular recess therein, a lo
cating projection ?xed upon the body portion of
said centering plug, and a removable holding
member, co-operating with the locating projec
tion for retaining said bit blank in saidpredetere
mined position and thereby locating said blank
a ‘predetermined distance from said annular re:
cess during the casting operation.
,3. ‘An apparatus for casting an accurately ,cen: '
tered diamond drill bitcomprising vacuum ,oharn,
they. permit the molten metal to ?ow therethrough
ber means, a die supported on the vacuum chains
ber means and in communication therewith, said
die having an annular recessv perforated. at the
more rapidly and with less cooling‘ effect, as com
pared with the closed holes 38.
bottom for individually seating a plurality “of
diamonds and a central aperture-concentric there;
forming a series of downwardly open slots or
grooves. The advantageof the open slots is that
What is claimed is:
.
with, a ?ask ring supported on the die against
1. Apparatus for casting an‘accurately centered
lateral displacement relative thereto and adapted
diamond drill bit comprising a die having an an_
nular recess perforated at the bottom for indi
vidually seating a plurality of- diamonds and a
central aperture, means cooperating with said
die for receiving and retaining molten metal in
to receive and retain molten metal during, the
‘association therewith during casting, means for :
producing suction through the perforations in
said annular recess past said diamonds to retain
the latter in position, a centering plug. having a
body portion adapted to extend through and sup.
port a bit blank in predetermined position above ~
thedieand terminating at one end in a central
tip of reduced diameter, said central tip being
adapted to ?t into the central aperture in said die
concentric with the annular recess therein, and
means upon said centering plug for locating said
bit blank a predetermined distance from said an,
nular recess durinsthe casting operation.
casting operation, a centering plug adapted to
slidably support a hollow externaly threaded bit
blank in a predetermined position above thehdie,
said plug having a pilot portion located in the
central aperture of the die to position the blank
concentric with the annular recess therein, said
plug having a radially-extending ?ange serving. as
stop for locating the bit blank upon'the plug,‘ and
an internally threaded removable cap passed
down upon the plug and adapted to‘ cooperate
with the flange and the externally threaded bit
blank to locate and retain the bit blank in a
proper position relative to the annular recess of
the die during the casting operation,
'
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TUcKEa
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