US1866082A - Expansion drill bit - Google Patents

Description

July 5, 1932. A. E. CARLSON EXPANSION DRILL BIT 4 sheets-Sheet 1 Filed Aug. 10 1927 III....

y 1932- A. E. CARLSON ,082

' EXPANSION DRILL BIT Filed Aug. 10. 1927 4 Sheets-Sheet 2 J6 5 34 gz 25 41 d6 65 Y Z V July 5, 1932. A. E. cARLsoN 1,366,032

EXPANSION DRILL 1311' Filed Aug. 10. 1927 4 Sheets-Sheet 3 fM/s vrax" WY'TO/PA/EX July 5, '1932. I E, CARLSON 1,866,082

- EXPANSION DRILL BIT Filed Aug. 10 1927 4 Sheets-Sheet 4 7417] GPA/.53.

Patented July 5, 1932 l ANTHQNY\ .E. .GARLSQ1\I, on Losnn-Grmns; GALIEORNIAf ExrANsron nnrLLrm 1 Application filed August 10, 1927'. Serial No. 211,972. r

My invention relatesto'the deep well-drilling: art: andmore particularly to bits: used as it] drills the hole-for it, the drill being withrotary. drilling; equipment.

Such; rotary equipment includes drill 3 pipe? having drill .bitprovidedon its lower end. The drillpipeextends vertically into the-earth andis rotatedby a rotary table of thederrick to cause the bit to form a hole. Asa-he bit employed usually has a fixed diam- 1 at. thebottomeiflthe hole. 'Then; afterthe cement hasl h-ardened, a smaller drill bitiwhich will pass down inside the casing is used" to;

drill through the cement'and deepen the hole.

The deepenedportion of the hole is thenproe' -Vided witha second-casing which. extends through the first casing and 31s cemented 1n placentatherbottom ofthe deepened'portionv H g sltlonsin which they were closer 'together' ofthe hole. The drilling of the hole is then continuedawith astill smaller bit WlllClPWlll pass throughthe second casing. The. hole thus; formed receives athirdand still smaller-s casing Whichxis: extended down through the" secondcasing .Thusgthedril'lin g10f the well continues. until oil is reachedi using-'a'bitof fixed diameter; as above. outlined, each successively deepened portion. of the hole isottsmallen diameter than-the casing through which a bit must be'passed to fornrthat deepened portion Thus, when the "drill bit and stem are. Withdrawn and a casing extended down into this deepened por-Q tion, there is very little spacebetween the from the wellz-bylthis cement. g

It isxan object ofmy invention to provide *anexpansion drillbit which may 'beexp'andedg after passing througha casing or after it has been owered. to the level where itis'toj be operated so-that' the holeiormed-bene aththat casing I may: be: larger than the diameter of I vention areillustrated. 1

\ several formsjofdrill bits enibodyingniyf in 6 It isanother object to provide an expansiondrillbltwliich may-be followedby the casing 7 adapted to be; contracted and withdrawn through this casing. y x

Expansion bitshave been previously pro-- vided, but these have had' a't'endencyto' collect'mud on the 'cutters s'oas to; form. a-liard ball on the bit so; thatthe bit cannotbe Withloeterawhich is larger thanthe'inside diameter of thecasingto be put-in the hole,-:the hole" is formed to a desired depth and the drill: stem; withdrawn, after which; the. casing is extended into the .hole and cemented in place drawn. upward throughthe casing through which it was extended into the well. Thus, 1t isnecessaryto waste a considerable length of time waiting for. the ball Of l jd; formed on the bit to'dissolve so that the bit may be collapsed'a'nd withdrawn through the casing;

It is' a furtherj object of my invention 'to provide an expansion drill" bit which isv adapted to be operated to break up andremove a ball of dirt wheneversuch a' ba-ll starts to form on the bit. I j v Expansion bits heretofore produced .re-1 'quired' the collapsing of'the cutters into: po

than when ext-ended' into' cutting positi'onyin. order that the bit might. be" withdrawn 5 through the casing. Many times such contraction is. made impossible dueto the pres ence ofi detrit us'between the cuttersrwhic hi keeps the cutters separated and'preventstheir. moving into retractedorcollapsed position: It is yet another object of my invention to provide an expansion drill bit in which a space between the cutters isgreater 1 when these are in retracted or'col lapsedj position than when these cuttersare extended po sition.- g I 7 It is of'vi'tal importance to the proper operati'on ofan expansion drill-I'bi-t that" the parts thereof'be fr ee at all tirnes to havefthe proper movement relative to. eachfothera i It i's-a zfurther object of.my invention to provide an expansion drill bit in which this freedon'rofthe parts ofthe bit isrnaint'ain'ed T by a flushingiaction of'a lubricating-sfluidsup plied thereto. r

Further objects :and' advantages -will be made manifest in the following'description 7 and in the accompanying drawings inwhich 5 In the drawings,-' I

Fig. 1 is a side elevational view of one embodiment of my invention with the cutters thereof in extended position. I

Fig. 2 is a view similar to Fig. 1 in whic the cutters are moved to retracted position.

Fig. 3 is a bottom plan view of Fig. 1. 1

Fig. 4 is a bottom plan viewv of F ig. 2.

Fig. 5 is a vertical sectional View taken on the line 55 of Fig. 3. I 3

Fig. 6 is a horizontal sectional view taken on the line 66 of Fig. 5.

Fig. 7 is a vertical sectional view taken on the line 77 of Fig. 3.

Fig. 8 is a horizontal sectional view taken on the line 88 of 7.

Fig. 9 is a vertical sectional view similar to Fig. 5, illustrating cutter parts'of the drill bit shown in Fig. 5, shifted downward into ,zrsecond form of the bit of mylinvention.

Figs. 14 and "15 areihorizontal.sectional views taken on the correspondingly numbered lines of Fig. 13. v, V r I 16 is a bottom plan view of Fig. 13

partially in section for illustrating the niounting of the cutters upon .theirsupports;

- Fig. 17 is a side elevational view of the drillbit, shownin Fig. 13, taken front the same view-point and showing the cutters, thereof disposedin retracted position.

I Referring'specifically to the drawings and particularly to Figs. 1 to 8, and Hand 12, the numeral 20 indicates one embodiment of the drill bit ofgrny invention. This bit includes a body 21 which'has a slight upward taper and which is provided with a threaded 1 pin 22 at its-upper end for securing it to the 7 lower. end of a drill stem. Extending upward into the body 21 are bores '23 which are identical in shape and symmetrically formed onopposite sides of the axis of the body 21.

. The upper end of each ofthe bores 23 is con- 'necte d by a rotary mud passage 24 which leads to the top of the pin 22 so as to connect 5 zwith thesupply passage of the drill stemv to which the pin is attached. Formed in the body 21- so that each connects with the upperportion of one of the bores 23 are two threadeddetent' pinholes 25. The upper portion" of the bores 23 are substantially cylindrical, while'the lower portion is enlarged toward one side thereof. to form a. semiannular frusto-conical cavity 271 I Each cavity-'27 has radial abutment'faces 28 and 29. V

' Extending upward into each ofthe bores 23 is one of a pair of identical cutter supports 36. Each of the supports 36, as clearly shown in Fig. 12, has a cylindrical shank 37 which extends into'the upper portion of the bore 23, the shank 37 being turned down at its upper end to provide a pin 38 and a bearing seat 39. Formed in the shank 37 a slight distance below the bearingseat 39 is an annular detent channel 40. Formed integrally with the lower portion of the shank 37 is a. semi-annularLfrusto-conical shoulder from which a cutter supporting arm 46 extends downward. Formed in the lower end of the leg 46, with its axis disposed in crossing relation with, and to one side of, the axis of the shank 37, is 'acutter pin bore 50. Adapted to be mounted upon the arm 46 is a cutter 51 which, in the present instance, is-shown as a discv cutter. The cutter 51 has a central bearing hole 52 and bearing bushings 53 countersunk into opposite faces of; the cutter 51 and surrounding the hole 52. Passing. through the hole 52 and vthe bushing. 53 and extending in the bore by "a key pin 56 which is driven into a suitable: holebored through thearm 46 and the cutter pin55. .The cutter. .pins are on horizontal axes A-A which are offset a distance B from the-axes C'C of the sup-- ports36;

Extending longitudinally through each cutter support 36 'is a main lubricating fluid passage 60, the upper end of whichis disposed opposlte the lower end of one of the fluld passages 24-forrned inthe bit body 21 and the lower end of which opens from the bottomof the cylindricalshank 37 so that the axis thereof intersectsthe upper. edge of the cutter 51 carried by thatsupport 36. Lateral fluid passages 62are formed in each shank 37 and lead from thecentr'al passage therein to the peripheral surface'of the shank.

Other lateral openings 63 are formed in each shank 37 which lead fr omthe central fluid passage 60 and open on oppositesides of the shoulder 45.

In assembling the bit 20, an anti-friction thrust bearing 65 is placed around the pin 38 on each cutter support 36 so that when the supports'36 carrying the cutters '51 are extended upward into thebores 23, the thrust bearings 65 abut against the upper ends of the bores 23 so as to permitfree rotation of the supports 36 in the bores 23 within the lnnitsdescribed hereinafter. The supports 36 are retained against removal'from the bores 23 by threaded detent pins 68 which are secured into the threaded holes 25 and project into the detent channels 40.

When the supports 36 are thus -.assembled on the body 21, the shoulders 45 are disposed in the cavities 27. As clearly shown-in Fig.

6, the shoulders 45 are formed with their it was extended;

outer frusto-conical surfaces co-aXial with the axis of the shank'37 so-that each shoulder 45 is free to rotate in itsrespective cavity 2'?- as its shank 37 rotatesin a bore 28. This rotation of the shank 37 is limited, however to the angular movement between the posi'-' tion' in which the shoulder 45' abuts against the abuting face 28 and the position inwhich that shoulder abuts against the face 29. As clearly shown in Figs. 3 and 4, the cutters 51 are disposed in extended or cutting position when the shoulders 45 abut against the faces 29, but are disposed in retracted or collapsed position when the shoulders 45 abut against the faces 28. I!

'Theoperation of the bit 20-is as follows: The bit is secured upon the lower endofthe drill stem and advanced downward through a string of Well casin which is slightly-larger than the maximum diameter of the body 21 and while the cutters 51 are in retracted position, as shown in Fig-45.. As the bit passes out of the lower end ofthe'casing and approaches the solid earth at the bottom of the hole, the drill stem is rotatedin a righthand direction which causes the cutters-51 to engage. the earth and rotate the supports 36 ninety degrees, so as to bring the shoulders.

tated, will form. a hole considerably larger than the diameter of the body 21 and also larger than that ofthe casing through which Referring particularly to Figs. 3 and 4, it will be seen that'the'axes C@ are eccentric of the body 21," and fur ther that the axes A. l A are eccentricof the body 21 and also'of axes C-C. Thus thesup ports 86 are of the-trailing orcastor type and when they are rotated on their axes C'C, the axes A-A are rotated-around the axes C-G; therefore when the supports IOiSQtQfIOIH the positionsshown in Fig. 4 intothe positions shown in Fig. 3, the cutters 51 will be swung bodily outward with respect to the body 21, and will= occupy cutting position as shown. While the bit 20 is being lowered to operating position and also while it is being operated, the circulation of lubricating fluid, which in general practice is rotary mud, is maintained at alltimes. Thispasses down through the drill stem, the drill bit passages 24 and 60, and after lubricating the parts of the bit 20,. passes upward "through the easing carrying with it the detritus which has been formed by the boring action of the drill.

Each shank 37 hasatairly loose fit in its respective bore 23 so that rotarymud will i'iow through the lateral passages 62 and downward between the supports 36 andv the bores 23. This keeps this space freefrcm dirt-or other material which might otherwise be forced thereinto-so as to prevent easy r0- tation of the cutter supports 36 when it is desired to swing these to extend or-retract the cutters As shown.particularly in Figs. 8 and 6, a portionoteach oi the cavities 27is open when the shoulders 45' are in either of their entreniepositionsin these cavi- 27 so astomaintain this entirely clear and thus permit the shoulder 15" to be rotated at any time in this cavity for thepurposeor manipulating the cutters of the bit. 1' l i As clearly shown in Figs; 5 and .9, the width of the annular deten-t channel 40'ofeach cut ter support 36 isgreater' than the diameter of the inner portion of 'thedetent pin 68 which projects into this channel, and the detent pin, 68 is. so disposed that when the'weight of thebit is placed upon the cutters thereof, the cutter supports 36 are moved upwardiso that there is a slightspace between the upper :face of the channels 40 and the detent pin 68. Thus, when the weight of the bit 20 is raised from the cutters 51,v the supports 36 drop downward a suiiicient distance so that theiipper face of the channels iO engagesgthe' detent pin. as shown in Fig. 9. This leaves a slight space between each of the shoulders. 45 and the surface of the cavities'27 so that the'lubricating flui d discharged from the lateral passages 62 washes downward-between the O11tQr'1 2CQS'Of. l18 shoulders45 a-nd ad iacentportions of the surfaces of the cavities 27, This .flushes out any, foreign matter ugnichinayihave become lodged inthe space Referring specifically to Figs. 13 50-17 inclusive,.a secondform of thebit ofinv in vention is indicated by the-numeral 80. i The bit has a body 81 which is substantially cylindrical in shape and is providedwith in threaded pin 82 which extends upward there'- from "and which is adapted to connect with the lower end of a drill stem upon which the bit80 is adapted to be supported and operated. Extending downward from the upper .end of the pin" 82 into-the'body 81 areniain body 'fluid passages 84:, the lower end of each of which connects to the upper end of one of a pa r of bores 85 which areidentical and which its are disposed symmetrically. on opposite sides of the axisof the body The bores 85 are formed 'upwardsfrom the lower end of the body'81; and have openings 86 at their lower ends which comunicate laterally with the exteriorof the body 81. Formed at opposite ends ofeach of the openings 86 are abutment faces 87 and 88. Formed centrally'in the y body 8'l-is adetentpin bore 90. Connecting the inner end of the bore 90 with the opposite side .ofthe body 81 is a detent' pin-locking are identical.

' cludes a substantially cylindrical shank 96 which has a .pin 97 of reduced diameter formed at its upper end to'provide a bearing shoulder 98 at the'base thereoffDisposed about the pin 97 to rest against the shoulder V 98 is an anti-friction thrust bearing 100.

E.E.which are offset distances G from the ters of my bit are disposed outwardrfrom the axes of their respective cutter supports in Formed in the outer surface of the shank 96 a slight distance below the shoulder 98 is an annular detentfchannel 101. Formed integrally with the lower portion of the shank 96 is a shoulder 103. Also formed integrally with the shank 96 and extending downward therefrom are cutter supporting arms 105 and 106, the lower ends of which are spaced apart and provided with aligned cutter pin holes 107and 108in which a cutter pin 109-is received and upon which a cutter 110, which in this instance is shown as a disc cutter, is rotatably mounted between the legs 105 and 106. The cutter pins '109 are arranged on axes axesFr F of'the supports 95.

Extending longitudinally through each support 95 is a central lubricating fluid passage 115, the upper end of which is disposed opposite the lower end of the body fluid passage 84 and the lower end of which opens directly'overthe' cutting edge ofthe cutter 1 110 which is mounted uponthat support 95.

Connecting each passage 115 with the ex terior of the shank 96 are lateral passages 120. The central'passage 115-is also connected by laterals 122 to channels 123 which are formed in the peripheralsurfaceof the shank 96 so as to be symmetrically disposed in opposite directions from the axis of the shoulder' 103 whichpasses through the axis of the shank96. H

I In assembling the bit 80, the shanks 96 are extended upward into the bores 85 so that the thrust bearinglOO bears against the upper endof the bore 85. The shanks are then rein place by a machine screw 131 whichextends through the bore 91 formed for that 'urpose. As clearl shown in Fi 14 o osite portions'of the pin'130 projectinto the detent channels ,101 of the cutter support shanks 96 so as to prevent the latter being withdrawn from their respective bores 85.

The shanks 96 have a sufliciently'loose fit within the bores 85 so that rotary. mud supplied to the bit 80 will flow from the body passage 84 and the central cutter support passages 115 through the lateral passages 120 and downward through the space between the support shanks '96 and the inner surface ofthe bores 85. i .Thebit 80 operates in identically the same manner as'the bit 20.- A particularly novel featurerof a bit 80 is the provision of the cavities 86 so that these open outward and sothat there is almost no chance whatever for these to be filled with detritus sons to prevent the operation of the bit. The shanks 96 may be rotated between the positions in which the shoulders 103 contact the abutment faces 87 and the positions in which the shoulders contact the abutment faces 88. In order to wash out any detritus which might be disposed in the open portions of the cavities 86, a constant stream of fluid flows outward through the lateral passages 122 and the semi-annular channels 123' while the shoulders 103 are moving towards one of the abutment faces 87 or 88.

. Another important feature of the bit 80 is theprovision of the arms 105 and'106 upon each of the cutterrsupports'95 as amounting for the cutters 110. -The cutters are thus mounted in an extremely rigid manner so that there is no possibilitythat they could be broken from the bit by strains incident to the ordinary use thereof.

Owing to the fact that the axes of the cutplanes parallel to the cutting edges of the cutters, the cutter are practically selfclosing when the bit is drawn upward into the I ble for any detritus to become lodged between the cutters so as to prevent their being retracted. The greatest'single drawback of the expansion-bits previously devised is thus entirely overcome, as the possibility of the bitbecoming stuck in'expanded position is eliminated.

I claim as my invention:

1. In an expansion drill bit, the combination of: abit body; cutter supportspivotally mounted longitudinally therein; cutters rotatably mounted upon said supports, said supports being swingable about their longitudinal axes tomove said cutters between retracted and extended positions, there being circulation passages in said supports through which lubricating fluid issupplied to said cutters.

2. In an expansion drill bit, the combination of: a bit body having vertical journal recesses formed upwardly therein; cuter supports vertically journalled in said recesses to swing transversely about their vertical axes; cutters rotatably mounted on said supports; means for retaining saidsupports in said recesses; and stop means provided upon V auxiliary ducts are formed insaid supports said body andsaid supports, limiting rotation of said supports on said body between p si tionsin which saidcutters are retracted and position in which said cutters are extended' saidil stop means being so positioned relative to said cutters that the planes of the inner facescf'said cutters will move apart as said cutter supports move-into retractedpos1t1ons.

3, In an expansion dr ll blt, the combmation of: a bit body having recesses formed upwardly therein; cutter supports extending intosaid recesses and" rotatable therein; cutters provlded upon said supports; means' for retaining said supports in said recesses; and stop-means provided upon'said body and said supports limiting rotation of said supports on said body between'positions inwhich said cutters are retracted and positions in which said cutters are extended, there being circulation passages formed in said body and said supports through which lubricating fluid is supplied to said cutters.

4. A combination asin claim 3 1n which which said cutters'are retracted and positions in which said cutters are extended, said supports'having a degree of longitudinal movement in said recesses when said bit is lifted, said movementsettl'ng up a passage between said body and saidsupports, there being lubricating fluid supply means in said body from" which said fluid flushes through said passage until said bit is set down. i

6. In an expansiondrill bit, the

distance apart than the inner faces of said cuttersupports when said cutter supports are swung from retracted into expanded position;

7. In an expansion drill bit, the coriibina-v tion of a body; cutter supports pivoted to saidbody on substantially vertical" axes, saidv cutter supportsbeing all-times swingablebetween retracted and expanded positions;

cutters carried by said cutter supports, said cutters being positioned so that imaginary lines drawn throughtheir centersat right angles to the planes of their cutting edges do not intersect the axis of said cutter supports;

combina-- tion ofza body; a pair of cutter supports atall times swing'ab'l'e on said body on a vertical 1 axis; said cutter supports being swingable substantiallyninety degrees; and cutters carried on said cutter supports in" such positions that the inner faces'of said'cutters are a greater;

and stops for limiting the swing ofsaidcutter I 7 supports; said stops being so positioned that thein'ner portions of said cutters moveapart as said supports swing from expanded to retracted position. V V

8}]?11 an expansiondrill b t, the combination of; a body; cutter supports pivoted to said body on substantially vertical axes, said cutter 'supports beingiatall times swingabl'e; V i

between retracted and expanded positions; rotary cutters carried by said cutter supports, said cutters being offset fromthe axes of said cutter supports; and" stops for limitingthe swing of said cutter supports, said stops being' so positioned that the inner portions of said cutters-will move apa'rt'as said supports swing fromexpan'ded to retracted position;

a 9 In an'expansi'on drill bit, thecombination of: abody; cuttersupports pivoted to said body on substantially vertical axes, said cutter supports being at all times swingabl'e:

between-retracted=and expanded positions; i

cutters carried by; said cutter supports, said cuttersbeing ofl se't'fromthe axes of said cutter supports; andstops'tor limiting the swing of said cutter'supports, said stops being;

so positioned that theinnerportionsof said cutters will move apart'assai'd supports swing from expanded to retracted position.

p '10. In an expansion drill bit, the combination of": "a body; cutter supports pivoted to said body on substantially vertical axes, said cutter supportsbeing 'swingable between re-- tracted and expanded positions; and cutters journalled on said cutter supports, said outters being rotat'able on horizontal axes not intersecting the axes of said cutter supports and-being so positioned that the projecting peripheries rot-said; cutters will provide vertically rotatable engagement means for producing movement of said cutter supports into, retracted positlon when said cutters are moved vertically into engagement with an obstruction;

1'1. In'an expansion drill bit, the combina-' tion ofz a bit bodyhaving recesses formed upwardly therein cutter supports vertically Ii Ournalled: in said recesses and at all times rotatable therein cuttersprovided upon said supports means for retaining said supports in said recesses; {stop meansprovi'ded upon said body and, saId supports, llmlting "rota-i tionof said supports on said ,body between positions in which said cutters are retracted, and positions 1n which Said; cutters are ex-- tended; and means rorisupplying a washing fluid to said stop means.

12., In an expansion drill bit,'the combina-- tionoft abody; cutter supports pivoted tosaid body on substantiallyvertical axes, said cutter supports beingiat all'tilmes swingable between retracted and; expanded positions cutterscarried 'saidcutter supports ;;abut j ment faces on-said body and shoulders on said cutter supports, the :retracted' and" ex- 7 I 13.'I n an expansion to said body on substantially vertical axes,- said cutter supports being swingable between. retracted and'ex'panded positions; and disc panded positions of said cutter supports being thereby determined, there being passages ex-.

tending directly to the spaces between said abutment faces and shoulders for directing flushing fluid thereto.

drill bit, the combination of: a body; cutter supports pivoted cutters rotatable on said cutter supports, said not intersecting the supports.

cutters being rotatable on horizontal axes axes of said cutter 14. In an expansion drill bit, the combination of: a bit body having vertical journal bores formed upwardly therein; cutter supports having vertical pivot shanks extending into said bores and adapted for pivotal movement therein; disc cutters rotatableon saidv supports; means for retaining said supports in said bores; stop means provided upon said body and said supports, limiting rotation of said supports on said body between positions j in which said cutters are retracted and positions in which said cutters are extended; and means for supplying a washing fluid directly to said stop means. c

15. In an expansion drill bit, the combination of: a body; cutter supports pivoted to said body on substantially vertical axes, said cutter supports being swingable between re-.

tracted andexpanded positions; disc cutters carried by said cutter supports; abutment faces on said body; and shoulders on said cutter supports-the retracted and expanded positions of said cutter-supports being thereby determined, there being passages-extending directlytothe spaces between said abutj ment faces and shoulders for directingflushing fluid thereto. V

16. In an expansion drill bit, the combination of :--a body; cutter supports pivoted to said body on substantially vertical axes, said 7 i cuttersupports being'swingable between retracted andexpanded positions; rotary disc cutters operably mounted on said cutter supports, said cutters beingoffsetfrom the axes of said cutter supports; and stops limiting l the swinging movement of saidcutter supports, said cutters and said stops being so positioned relative tov said cutter supports 4 .jthat the inner faces of said cutters will move apart as said cutter'supports move from expanded to retracted position.

-17.'In an expansion drill bit, the combination of: a. body;'cutter supports of the castor type having cylindrical shanks piv- .oted to said body on substantially vertical axes and provided with depending trans versely offset legs swingable, between reposing said cutters wider apart in retracted position than in expanded position.

'19. In anexpansion drill bit, the combination of: a body, cutter supports of the castor type having cylindrical shanks pivoted to said body on substantially vertical axes, and provided with depending transversely offset legs swingable between retracted and expanded positions; and cutters carried by the free ends of the legs ofsaid supports, said cutters being disposed wider apart in the re-.

tracted position of said supports than in the expanded position of said supports.

i 20. In an expansion drill bit, the combination of a body, cutter supports of the castor type having cylindrical shanks pivoted to said body on substantially vertical axes and provided with depending transversely offset legs swingable between retracted and expanded positions; and rotary disc cutters carried by the free ends of the legs of said supports,

said cutters being disposed wider apart in the retracted position of said supports than in the expanded position of said supports.

21. In an expansion drill bit, the combination of: a body; cutter supports of the eastor type having cylindrical shanks pivoted to said body on substantially vertical axes and provided withdepending transversely offset legs swingable between retracted and expanded positions; cutters carried by the'free ends of'the legs of said cutter supports; and

means for disposing the confronting faces of said cutters wider apart in retracted position than in expanded position. r

22. In an expansion drill bit, the combination of: a body; a plurality of cutters having innerportions outlining a space; and

cutter supports for holding said cutters on said body, said cutter supports rotating relative to said body through arcs and, carrying the inner faces of said cutters into greater spaced relationship and at the same time carrying said cutters into retracted positions relative to said body. 7

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 5th day of August, 1927. r

, ANTHONY E. CARLSON.

tracted and expandedpositions; cutters car- 7 ried by the free ends of the legs of said cutter supports; and means for disposing said bit, the was.

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