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Патент USA US2111781

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" Q Patented
'22,’ 19738 ~
2,111,781 _. .
‘ 'sguis‘si'
' w'nu. panama nrrr >
John a. name, Huntington‘ Park. can.‘ a ‘
l’ " ‘Application July 0, is'ss, serial No. sass. *
‘ ‘ isolation.‘ mes-1.1»
This invention‘ relates‘ to a‘ well Pdrilling- tool
' and-relatesl‘more particularly to a ‘drilling bit tor
use in the rotary‘method oi‘well‘ drilling. A gen
.eral object of the invention‘is to' provide rpm;
scraper type cutter-to‘ clear its‘ cutting edge or
mud and‘ cuttinll,
‘The various objects and features of my inven
will be fully understood from the following
5 tical e?ective :‘wellgbit embodying an‘ improved detailed description of a typical
form ‘5 e
'and very eillcient combination of cutters. ‘' ~‘
and application of the invention,’ throughout
Another object otthis invention is to provide which description reference vismat‘le to the ac
f a rotary‘ well drilling bit in which the-outer or‘
peripheral portion oi?the well bore is drilled by
‘10 rotatable cutters of one type and the remaining
inner‘ portion of‘ the bore is :drilled by rotatable‘
rig. " 1 is a. ‘ side elevation . org-theimnroved bit
provided by this invention with a portion in ver- 10
tical ‘cross section" to'ilhistrate‘ the rotatable
cutters of: another typewhereby the maximum‘ mounting clone or the "scraper type ‘cutters
e?iciency of both forms or cutters is obtained.
Fig.‘ 2 ‘is an enlarged i'rsamentary- ‘vertical de- ‘
Another object of this invention is to provide .tailed seamen view taken mbstanti?l! as‘ in
15 a well Abit embodying roller type“ cutters-rotat dicatiad by line 29-! on Fig; ‘1.,
3 is a‘trans- is
ably supported for rotation‘ about substantially
horizontal or‘only partially inclined ‘axes to
lineH onsectional
Fig. i and
14 is aas
cut‘ an, annular channel at the periphery‘oi the
wellbore by‘a rolling and crushing actiomand
mien ormeba-
' The-rotary well-drilling bit oi'th‘e present in-‘
20? embodying scraper type cutters-"supported for vention includes. senerslly.A a shank or
ll, 20
rotation about nearly‘vertical ‘axes to vcut away
‘roller type‘ cutters I i_ rotatabiy' su “
the remaining portion of the‘boreby a scraping crushing
on the body It, and shearing o‘r
Anotheriobjectiof'ithis invention isto provide
The shank or body" "is
to becon- ‘
25 aiw‘ell bit or the character‘mentioned‘inwhich nected with the-lower end “of a‘rotsry
drilling‘ 25
the slightly tilted or ‘nearly verticalshearing type
orshearing' action.
cutters are self-sharpening" through‘ their‘ en?
gagementl with the earth formatio
AnotherAobject of this invention ‘iswto ‘provide
30 a bit of ‘the character ‘mentioned. in which vthe
slightly tilted or 1nearly ‘vertical scraping. type
cutters are‘ forced “to ‘rotate and; ‘therefore,
very e?icientand long.wea.rm‘g_ ‘ ‘V.
Another object of this "invention‘t'is ‘Atoms-wide
A 35 a novel and' highly e?icien't- ‘,forniof rotatable
string. Thebody ll may be integral and may be
generally cylindrical. Means is Aproyidedatthe
upper end of the body l'l-tofa'cllitate its connec-' -
tion with‘the‘ well drilling string. In the'vpa‘r-v
‘ticular case illustrated ‘atapered screw threaded 3d
ll isprovided in the upper end 01 the body
It to- receive spin on the lower end oi’ the drill
' ingstring.""1he.'lower-} end portion or the body
ll maybe enlarged in ‘diameten- "
II is .
"provided with pairs savings or legs is and II‘ to‘ ‘,5
‘‘ cutter for a well‘drilling bit whichcutter is in‘
receive and ‘carry the cutters II and their mount
tended tov be supported for‘ rotation‘ ‘about a v1118s.
In the‘particular embodiment of thejin
;-nearly vertical axis and‘ embodies reaming cutting vention
illustrated‘ there "are two ‘diametrically
teeth toassure its rotation;
‘1 "
opposite‘ pairs oflegsilland II, ‘The legs i4 and‘
A40 Another-“object 01' this invention is to provide I! are integral withvthe'body ll andpmléct 40
a well bit oi’ theucharac’ter mentioned in which
downwardly and outwardly ‘from its'lower ‘end.’
'I'he'legs II are the outer legsl'oi the pairs. and
which are dependably supported at both‘ their may be somewhat thibker than‘ the inner legs I}.
inner and outer ends.
The legs ll and II oi‘ each pair aresub'st‘antially
45‘ Another object oi this invention is to provide parallel‘ and are prqvidedmattheir inner sides 45
a well drilling bit of the‘ characterfmentioned in with ‘opposing ‘raised bearing surfaces‘ it,“ and i 6'‘,
which the nearly vertical rotatable “scraping cut-‘
the crushing ‘roller cutters‘ are mounted or: pins
ters are‘ devoidAof teethat their lo'w‘e'rfends and;
respectively. The lower outer _ corners ‘or the
outer legs II are bevelledto be‘substantially ver
thereforepare not as liable to.‘ failure as‘the‘
tical and ?at shoulders I! are provided on the
‘ .60 toothed nearly vertical‘cutterslheretotore‘introJ
lower ends of the legs I4 and‘ are mrhetanti‘ally'
A. Another object 01’ this invention is‘ toprovide a
well drilling bit of the‘ character‘mentioned in
which astream oi, circulation‘ ?uid‘ is discharged
‘55 A downwardly irom within the lower end oi‘each‘
normal to the surfaces M".
The lower
‘corners oi the legs ll maybe suitably bevelled
away'and ?at shoulders All are ‘provided on the
lower ends of,- these.‘ legs;
' .‘I'hebody n‘ is provided'withsp‘aced
is 55“
to carry the means for rotatably supporting the
cutters i2. In the embodiment of the invention
illustrated there are two substantially diametri
the roller cutters || operate to cut an annular
groove in the periphery of the well bore by a
cally opposite bosses l3 projecting downwardly at
are slightly inclined downwardly and forwardly
The cutters.|2 are an important feature of the
invention being of novel shape and construction. 5
The invention, as illustrated, includes two cutters
i2 which may be .alike in size and shape. The
with respect to the direction of rotation of the
cutters i2 are generally cylindrical though grad
5 the lower end of the body in. The bosses II are
partially cylindrical and their longitudinal axes
crushing rolling action.
bit. Due to the pitch or slight inclination of the '"uated or varying in external diameter. The cut
ters J2 are preferably, though not necessarily. 10
10 bosses i3 they are not directly diametrically op
posite but have their axes at opposite sides of a ‘ tubular. As illustrated in the drawing each cut
diametrical plane. The lower ends of the bosses ter l2 has a central longitudinal opening 30. The
l3 are flat and are normal to their longitudinal upper ends of the cutters ilarefiat and normal.
In accordance withlthe invention the cutters I2
The cutters II are operable by a crushing ac ,»are"'substantially cup-shaped having depressions 15
tion to form an annular cut or channel in the or central sockets'3l in their lower ends.
peripheral portion of the well bore. The cutters
II are in the nature of roller cutters.
The roller
cutters II have central longitudinal openings i9
20 and flat normal ends. Peripheral cutting teeth
23 are provided on the cutters ii.
The teeth 20
preferably overhang or project outwardly beyond
the outer ends of the cutters ||. The innerand
sockets 3| are comparatively large in diameter
and are provided to form or leave annular cut
ting edges 32 at the lower ends of the cutters.
The cutting edges 32 are the principal cutting 20
edges of the cutters l2 and have shearing or
scraping engagement with the earth formation
as will be hereinafter described. The extreme
lower ends of the cutters l2 are bevelled upward
25 ellecl off, as illustrated in the drawing. The ly and away from the cutting edges 32. The 25
teeth 23 may be straight or spiralled, if desired sockets 3| in the lower ends of the cutters I2
or found practical. The two roller cutters Ii provide or leave cylindrical. walls at the lower
may be identical in size and shape.
~ ends of the cutters and the edges 32 occur at the
The invention provides effective dependable lower ends of these walls.
outer corners of the teeth 20 are preferably bev-
30 means for rotatably supporting the roller cutters
The walls or surfaces of the sockets 3| are 30
|I between the spaced legs l4 and IS. The means
hard faced with tungsten carbide, or the like, to
for rotatably supporting the cutters || include
provide the cutters with long wearing cutting
bushings 2|. The bushings 2-|,are tubularrcylini ' edges 32. The sockets 3| are comparatively deep
drical members and are provided at their inner so that the edges 32 are very long wearing. As
the edges 32 scrape along the bottom of the well 35
35' ends with annular thrust'?anges 22. The flanges
22 areadapted to bearagainst the surfaces l5‘. bore the metal behind or ‘surrounding the edges
Extensions or lugs 23 are provided on the thrust 32 being softer than the hard facing comprising
?anges 22 and cooperate with the shoulders |'| the edges 32, wears away, leaving the edges 32
to prevent‘ rotation of’ the bushings 2| and to sharp. Due to the depth of the sockets 3| the
edges 32 automatically remain sharp until the 40
40 transmit upward thrusts directly to the legs I5.
The outer end portions 2| ‘ of the bushings 2| tubular lower walls of the‘ cutter |2 are almost
entirely worn away.
are reduced'in diameter and carry thrust wash
ers 24. The washers 23 are adapted-to bear out
In addition to the cutting edges 32 the cutters
wardly against the thrust surfaces It‘. The |2 are provided with reaming teeth 33. The
upper portions of the cutters l2 are’ enlarged in 45
45 cutters | i are rotatably supported on the bush
ings ‘2| between the ?anges 22 and the washers external diameter and longitudinally extending
'24.‘ In practice the cutters | I may be rotatably grooves 33' are formed in these enlarged portions
supported on the bushings 2| through roller
bearings 25. The ?anges 22 and the washers 24
serve to space the cutters II from the legs I3 and
ii and to transmit end thrusts to the legs;
of the cutters to form or leave the reaming teeth
33. The grooves 33‘ forming the teeth .33 are
preferably of substantial depth to extend into 50
the bodies of the cutters I2. The reaming teeth
Shafts or screws 26 are passed inwardly 33 extend from the upper ends of the cutters |2
through openings 21 in the legs l5 and have their 3 to circumferential lines spaced slightly above the
outer portions threaded in openings 28 in the legs, upper walls of the sockets 3|. In the drawing
‘II. The openings 21 and 28 are inclined down-J, the teeth 33 are shown as straight or axial, it 55
wardly and inwardly having longitudinal axes ‘, being understood that the reaming teeth 33 may
normal with the surfaces Ill and I5“. The be pitched or, spiralled, if desired. The teeth 33
screws 26 are provided at their inner ends with being formed in the enlarged upper portions of
heads 28' bearing outwardly against the legs IS. ‘the cutters i2 have active longitudinal edges for
The headed and threaded screws 26 serve to tie contacting and reaming the side wall of the well 60
together the lower portions of the legs I4 and IS. bore as will be more fully described. The cut
The screws 23 pass through the bushings 2| to ters i2 are preferably carburized throughout
support the bushings between the legs It and IS. their various surfaces, with the exception of the
Notches 29 are provided in the outer sides of the side walls of the sockets 3|,v to have hard inter
legs I‘ at the openings 28 and end parts of the nal as well as external surfaces.
screws 26 are peened into these notches 29 to
Simple, eifective means are provided to rotat
lock the screws against unthreading. The cut
ably support the cutters |2 on the body I0. In
ters || supported as just described are rotatable accordance with the invention the cutters I2 are
about downwardly’ and inwardly inclined axes rotatably supported for rotation about axes which
and project downwardly beyond the lower ends are slightly inclined downwardly and forwardly 70 of the legs i4 and i5 to act on the formation at relative to the direction of rotation of the bit.
the bottom of the well bore and project slightly Sockets or openings 34, having the desired slight
beyond the outer sides of the legs I4 to assist in inclination, enter the bosses l8 from their lower
cutting the bore to gauge. . It is believed that it
ends and extend upwardly into the body i0
will be understood by those skilled in the art how proper. The longitudinal axes of the openings 75
' 2,111,781
on the tool prevent the cutters l2. from being
and a cutter supported on the lowe end of the
subjected toexcessive feed pressures. ‘
‘body for rotation about a nearly. ertical axk,
‘ , The cutters l i ,and, the cutters I2,are depend- . there being an opening in the lower» end of the
ably supported ‘ ‘for independent ‘rotation ‘about
cutter leaving‘ a wall of tubular form which pre
individual axes. ‘The cutters ‘are supported
sents an annular scraping edge. said cutter in- '
so’ that they may be easily ‘and quickly removed
eluding hard‘ facing material lining the said sock
‘ for resharpening or replacement.‘ "The body Ill
et whereby said wall wears away through use to
is subjected to littleor no wear and'the various
maintain said edge sharp.
8. A rotatable cutter for a well drill including,
a cutter body intended to be supported for rota
10 .
vertical axis, said body 10
about "a generally
Having ‘described o y atypical preferred ‘form tion
having an opening
and‘ app cationormy, invention I do not, wish
be limited or restrictedto the speci?c details
forth, but , "wish
provide a cutting edge;
' y
‘9. A rotatable cutter for a well drill including,
a cutter body to be supported for rotation about
my invention.
bit including,
I claim."
a body,“ .
a‘ nearly vertical axis, said body having an open
ing in its lower end
‘a roller cutter rotatably supported on the body
‘ ‘ for rotation about, asubstantially transverse axis
and positioned ‘to make an annular cut in the andiraisedreaming teeth on the periphery of the‘
body above said’ edge.
g ‘
10. A well bit including, a bodyto be rotated in
tatably supported on the body'for rotationabout
an axis inclined downwardly and‘ slightly .i'or a well, ‘a rotatable cutter‘having a scraping edge I
peripheral‘ portion oi’ the "well, and a cutter ro
wardly relative to the ‘direction of rotation vof
at. its lower end and axially extending reaming
the bit and having?a‘scr‘aping edge for acting . teethon its'external surface, and means rotatably ‘
inner portion of the‘ well.‘ .
‘so ‘on'2.the
A rotary ‘well ‘drilling :bit‘including, a
a roller cutter ‘rotatably supported on the body
for rotation about a-substantially transverse axis
and‘ positioned "to make‘an ahnular‘cutirin the
peripheral ‘portion or "thewellyand “a cutter
rotatably supported on the body‘ i'onrotation
about an axis'inclined downwardly and forward
ly relative ‘tothe direction of" rotation of the
bit‘ythe last mentioned cutter having 'a contin
uous scraping edg 'jfor acting on ‘the'linnerpor
40 tionof the well‘bor;
cutter on the ‘lower end of the
. body to rotate about a downwardly and forward
' b
adjacent and substantially par
allelwith the side wall or the bore whereby the
said teethengage the side wall to cause rotation
j 11. A wellbit including, a body to be rotated in
a well, ‘a rotatable cutterlhaving a scraping edge
at‘ its‘lower end and axially extending reaming
teeth on its, external surface 01' greater enective
3.1,‘ A‘ rotary ‘ well drilling bit including, a body,
a roller‘ cutter rotatably supported on the body
‘ ' for. rotation about a substantially‘transverseaxis
and ‘positioned to make an, annular cutin the
peripheral portion or the well, and acutter' ro
tatably supported on
the body for rotation‘a'bout
‘ an axis inclined‘downwa‘rdly and forwardly rel;
ative‘ to the direction‘ of rotation of the‘ bit.‘ the
last mentioned cutter having a‘ continuous scrap
ing edge ‘for acting on' the inner portion ‘of the
well bore, and reaming teeth‘ for contacting “the
, side wall oi’ the bore to effect its rotation.
edge scrapeou the bottom of the bore and to have
its outer ‘peripheral surface adjacent and sub
stantially Darallel'with the side wall of the bore
whereby the" said teeth engage the side wall to
cause rotation 01'. the cutter.
12. ‘A well ‘bit including a body having a ?uid
opening, a pin carried by the body and projecting‘
‘from its lower'end, and a cutter rotatable on the
x 4. A rotary well drilling bit including, a‘ ‘body; pin about a- downwardly and forwardly inclined
and a substantially cylindxicalcutter supported axis,'said cutter having a'socket in its lower end
~55 on the lower end ofthe body for rotation ‘about , leaving an‘annular scraping cutting edge foract
“ an axis inclined
downwardly and forwardly relaV ing on the bottom wall of the bore, said pin ‘hav 55
tive to the‘ direction of rotation of the bit, there ‘ ing an opening, for, conducting ?uid from the
?rst mentioned opening to said socket.
being‘an .opening in the lower end of
the cutter '
leaving a-wall of tubular form'whose lower end
‘13. A'rotary well drill including, a body having
a pair-oispaced depending legs, a pin extend
5. ‘A- rotary well drilling bit including, a body, between said legs to have its ends supported
and a~cutterisupported on the .lower end' 01' the thereby, _a»roller cutter on said’ pin rotatable
bodyjtor rotation about
an ‘axis Iinclined down-‘r about a, substantially transverse axis to act on
presents an annular-‘scraping edge. .
wardly and slightly forwardly‘ relative to the
the bottom wall of the well, and a- scraping cut
direction 01' rotation of the‘ bit, the cutter in-v ter rotatably supported 1 by the body to rotate
cluding an endless. scraping Jedgeon its lower
6. A. rotary well
‘drilling :bit includins, a body.‘
and afcutter supported on the‘ lower end ‘of the
about a ‘slightly downwardly andtorwardly in
clined axis to act on the bottom wall of the well.
14. ‘A rotary well drill including, a body, sub;
stantially diametrically opposite pairs 01' spaced -
body 101- :rotation, .abon'tan axis inclined down , legs projecting from the lower end 01' the body,
wardly and slightly forwardly relative to>the di-" pins supported‘by said‘ legs, roller cutters ‘sup 70
ported on said- pins i’orrotation about down
rection oi rotation ‘or the bit,’ the cutter includ
wardly andginwardly inclined‘axes to have roll
ing an endless, scraping edge on its lower end,
and reamingteeth above, said edge.
ing‘ contact with‘the peripheral portion of the
7. A rotary well ,drillingbit including, a
bore, and cutters rotatabLv supported‘ by the
- body between said-pairs oi’ legs to rotate about
from the chamber 55 to the spaces between the
adjacent legs l4 and I5. The ports 5| are in
and the openings 34 are tapered being of up
clined downwardly and outwardly and direct the
wardly diminishing diameters. The means for circulation ?uid against the cutting teeth 23 of
rotatably carrying the cutters |2 include studs the cutters II. The upper ends of the openings‘
or pins 35 arranged upwardly in the openings 34. 34 are in communication with the ?uid chamber
The upper portions of the pins 35 are tapered to 55. The cutter supporting pins 35 are tubular
properly fit the openings 34.
having central longitudinal openings 52. The
Means are providedv for removably lockingthe upper ends of the openings 52 are in communica
pins 35 in the openings 34. *Transverse openings
with the chamber 55 while the lower ends
of theopenings 52 communicate with the sockets
10 35 are provided in the bosses I3 and intersect-‘or
partially join the openings 34 adjacent their 3|. The openings 52 conduct the circulation ?uid
outermost walleportions.~ The openings 36 are downwardly from the chamber 50 to the sockets
elongate in cross section and have their major 3| to effect the full flushing and cleaning of the
transverse axes incl'ine’d downwardly and out
active cutting edges 32 of the cutters l2. ''
" 34 are normal to the lower ends of the'bosses l3
15 wardly. ’ Notchesflfare provided in the exteriors
In the operation of the bit provided by this '
1 ‘
‘of the pins 35 to complement or communicate invention the body It carrying the various other
‘a with..__the¢ openings 35: Wedges 33 are arranged _ parts of. the tool is connected with the lower
or driven'in the open'ings35qto cooperate with the end of a suitable well drilling string. The drill
notches 31. The end portions or at ~~least ‘the ‘in'g string is lowered into the well and is rotated 20
20 small end portions of the wedges 33 are turned
' over to prevent accidental displacement of the
wedges from the openings 35. The wedges 38 co
operate with the notches 31 to dependably lock
the pins 35 against displacement from the open
25 ings 34 and serve to hold the pins against rota
tion. The pins 35 project downwardly from the
bosses l8 and the cutters | 2 are rotatable on the
projecting portions of the pins. The pins 35
project through the openings 30 in the cutters
30 l2 and have annular ?anges 40 at their lower
ends to prevent displacement of the cutters. The
?anges 40 are preferably received in annular re-.
‘cesses4i in the upper walls of the sockets 3|.
and fed downwardly in the'usual manner to ad
vance the bit into the formation. The roller
cutters II are formed and positioned to cut; a
relatively narrow channel in the earth formation
at the periphery of the well bore. This cut formed 25
by the cutters II is slightly less than the de
sired gauge of the well bore. The cutters || op
erating by a crushing or rolling action take or
transmit a substantial portion of the feed pres
sures on the bit relieving the cutters l2 of ex
cessive feed pressures.
The cutting edges 32 of the slightly tilted cut
ters |2 have scraping engagement with the bot
tom wall of the well bore within the cut made
Hardened thrust washers 42 are preferably in-v
terposed between the upper endsof the cutters
|2 and the lower ends of'the bosses l3. Suitable
by the cutters ill. ‘ The cutting edges 32 being 35
endless or annular have smooth even engage
thesame by a scraping action. As above de
scribed, the side walls of the sockets 3| are hard
faced with tungsten carbide or the like to pro 40
dowels 43 hold the thrust washers 42'against r0~ ’ ment with the formation to effectively cut away
The cutters l2 are rotatably supported on ‘the
pins 35 to rotate about approximately vertical
axes, the axes of rotation of the cutters being
slightly inclined downwardly and forwardly rela
tive to the direct rotation of the bit. Thus the
lower ends of the sockets 3| on the cutters l2
are open and trailing portions of the cutting
edges 32 have shearing or scraping engagement
with the formation at the bottom of the well
vide the cutting edges 32. As the tool operates
the relatively soft metal surrounding and back
ing the cutting edges 32 wears away leaving the
edges 32 sharp. The metal surrounding the
edges 32 trails the edges 32 as they engage the 45
formation and these trailing parts of the cutters
|2 are worn away more rapidly than the edges
bore. The active portionseof the cuttingedges ‘ 32. Further, asmall core may be left standing
32 are in substantially the same horizontal plane between the cutters i2 and the lower outer parts 50
as the edges of the teeth 20 where they contact of the cutters I2 may be worn away due to their
engagement with the core. The lower outer por
the formation. The scraping cutters l2 are po
sitioned and mounted so that their peripheral tions of the cutters |2 are relatively close to the
surfaces are substantially vertical where they are center of the bit and are moving at a relatively
opposed to and adjacent to the side wall of the
55 well bore so that these surfaces move in a circu
lar path larger in diameter than the circular
paths of the outermost surfaces of the bosses l3
and legs |4. Owing-to this disposition of the cut
ters H the reaming teeth 33 come into positive
60 cooperation with the earth formation and are
substantially vertical as they engage the side wall
of the well. The engagement of the reaming
teeth 33 with the side wall of the well bore reams
the bore to gauge and effects the positive rotation
65 of the cutters l2 about their individual axes.
This independent rotation of the cutters l2 ren
ders their edges 32 more effective and long wear
The invention provides means for flushing the
cutters H and I2 of cuttings and mud. A ?uid
chamber 50 is provided in the body II! at the
lower end of its socket l3. The chamber 50 re
ceives the circulation ?uid pumped downwardly
through the drilling string. Ports 5| are pro
vided in the body l5 and extend downwardly
high velocity when they engage the core and,
therefore, wear away rather quickly. This wear
ing away of the metal about the edges 32 auto
matically maintains the edges 32 sharp. Thus
the cutters l2 are self-sharpening through use.
The reaming teeth 33 have a larger effective 60
diameter than the edges 32 and cutters II and
engage the formation at the side wall of the well
bore to cut the bore to the desired gauge. This
reaming engagement of the cutting teeth 33 with
the side wall of the well bore effects the positive 65
rotation of the cutters l2 making the cutting
edges 32 particularly efilcient and long wearing.
It will be noted that the cutters'i2 present end
less or annular principal cutting edges 32 for
acting on the formation at the bottom of the well
bore and do not have projecting blades liable
to breakage or failure. The cutters II and I2
are spaced and related to assure the smooth even
operation of the tool. The roller cutters II in
taking a substantial portion of the down feed 75
‘ downwardly‘ and‘ slightly forwardly inclined aires
16. A rotary well drill including, a body, sul1~ ‘ ‘
to have scraping contact with the bottom‘wall 0t ‘ stantlally diametrically opposite pairs of spaced
‘ the‘ bore.
.15.‘ A rotary well drill including,- a body, sub:
' ‘stantially ‘diametrically opposite pairs of spaced
legs projecting from the lower end of the body,
pins supported by said legs,‘ roller cutters sup
‘ ‘ ported on said pins for rotation about‘downward
‘ ly‘and inwardly inclined axes to have rolling con
tact with the peripheral portion of thebore, and
cutters rotatably supported by the body between
said pairs ‘of legs ‘to rotate about downwardly
and slightly forwardly inclined axes, the last
mentioned cutters having scraping edges at'their
lower ends contacting the bottom wall or the well
and reaming teeth contacting the side wall ‘of
the bore.
legs projecting from the lower end of the body,
plns supported by said legs, roller cutters sup
ported on said pins for rotation about downward
ly and inwardly inclined axes to have rolling con~ ‘
tact with the peripheral portion of the bore, and l >
cutters rotatably supported by the body between
said pairs of legs to rotate about downwardly
and slightly forwardly inclined axes, the last 10
mentioned cutters having annular scraping edges
at their lower ends contacting the bottom wall
of the well,’ and reaming teeth of longer e?ective
diameter than the lower portions of said‘cutters
‘contacting the side wall of the bore.
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