US2325535A - Drill - Google Patents

Description

July 27, 1943. A. J. NORDBERG 2,325,535

INVENTOR.

July 27,1943 A. J. NORDBERG ed Oct. 28,V 1941 2 Sheets-Sheet 2 Patented July 27, 1943 i,ll\ll'l'EDY STATES PATENT OFFICE f V 1 2,325,535 A DRILL Albert I. Nordberg, Detroit', Mich. Application (lct'ober 28, 1941, Serial No. 416,851v

7.Y Claims;

This invention relates to the manufacture -of rifle barrels and has for its principal objects to provide a new and improved construction of a drill especiallytadapted for such work by means of which the rate ofr production is greatly increased and the cost of manufacture decreased. The drilling ora rie barreL- and particularly barrels for military rifles, has, with the production nfiethods heretofore employed,-been a very diiiicult, time consuming operation that` was capable of being performed only by-the most highly skilled mechanic.' The barrels of military rifles are quite long, usually from .45 to 90 inches in length, and have heretofore been finished by the use of a special drill which must of necessity be longer than the rifle barrel. As the'bore of the barrel must be perfectly straight and smooth, great care must bel employed to prevent the tool from scoring the gun b-arrel as the result of gouging or as a result of the accumulation o-ipchips and consequent seizing of the drill in thebarrel'and like- Wise. great care mustbe exercised to prevent the drill from drifting sidewise during the drilling operation which'would Vresult in the production of a bore thatisnot perfectly straight. Allowable tolerances being ofthe nature'of fractions of one thousandths of an inch; the most meticulous accuracy is required.

It has beenrfound that because of the great length of the; barrel relative to the diameter thereof, barrels couldnot be drilled or bored by the use of an ordinary twist drill or by the use of a boring bar, and it has been the practice for many years to employ a special single iluted drill in which the ute provided for chip clearance extends parallel withV the axis of the drill. Such drills as heretofore used have almost universally been mounted horizontally in special machines which have required the services of highly skilled mechanics for their operation anddue tofthe great length of the drill and its comparatively small diameter, such drills as heretofore used have had but veryslight resistance to torque. Consequently thel operators of the gun barrel drilling machines have had to develop an almost uncanny ability to perceive almostl instantaneously when, in drilling a gun barrehthe torque thrown upon the drill threatened to become great enough, either as a result of chip accumulation or from any other cause, to throw the cutting edge of the drill out of proper alignment or to place strain enough upno the drill as to cause it to break.

a piece of steel tubing, one sidewall of which has been pressed or rolled tokprovideuthe chip clearance flute and to the end of which tubing a piece of tool steel has been brazed or Welded toform the cutting end or bit of the tool. Due tothe manner in which the shank portion of the cutting drill has beenlfabricatedtby pressing in o ne side wall of the tube to` form a chip clearance flute and also to provide an oil passage 'extending longitudinally through the shank, a very definite limitation has of necessity been imposed. upon the thickness of the wall of the tube employed.

Among the'principal objects of the present in-V vention are to` provide a new and improveddrill for the fabrication of rifle barrelsin which the shank portion of the drill is constructed of la tube having a much'thicke'rrtube wall than heretofore employed so that the drill can withstand Aheavier torque strains and to obtain the desired shape of chip clearance iiutewhile insuring an outerconsuflicient volume, all of the above described resuits being obtained as the resultV of a novel method of fabricating the drill shank as will -pr'ersf ently be more fully described.

Another object is to provide a drill of this character ,withA a cutting bit portion formedof the well known tungsten carbide type` of material such as sold under'various trade names as for example Carboloy. f l

A further object is to provide anew and im-4 proved construction of the4 means for combining thel improved type of drill shank with a'phigh speed cutting bit toform4 a unitary structure and to unite the cutting bit portion with the tool shank in such a Way that a smooth continuous outer surface will be formed on the drill and further to provide the cutting bit portion with lands and relieved portionsiadiacent thereto that vwill eiiectu'ally cooperate with the drilled or ,bored portion of the hole to prevent any lateral drifting of the drill Vduring the boring operation While Drills, as heretofore employed for this purpose, W

have consisted of a main shank portion formed of at the saine time'insuring proper clearances lfor effective cutting.

The above and other objects of the invention Wlli appear moreY fully fromthe followinglmore detailed description and by reference to the accompanying 'drawings forming a part hereof, wherein: A A t Fig. 1 is 4.aside elevationrshowing the improved manner inrwhich the drill of the present invention is employed in machining the bore of a 'riile barrel;

"vFiguZ is a plan view of the cutting end of the drill as seen from line 2 2 in Fig. l;

Fig. 3 is a longitudinal section taken along theA line 3--3 of Fig. 2 and showing the component Yparts of the drill united to form a unitary struc- .Fig. l2 is a perspective View of such shank por` tion when in nished condition.

As shown in the drawings the drill bit of the present invention comprises a main shank portion 20 constructed of steel tubing in a manner presently to be described more fully, an yintermediate tool bit holder portion 22 and a" cutting l bit or tip 23. The shank portion 2B of the drill,

'as' clearlys'howrlv in Fig. l2, is provided along substantially; its entire-length" with aflongitul din'ally fextending u'te V2li to'V provide for 'chip clearance. Afterf the r:shank -prtiori` has been fabricated thetool bit holder 22 which may" be constructed of highY carbon steel, is secured to the end of the shank portion 2l? anordinary brazing; as indicated' by'the reference character 25.\-"1`he^intermediate bit holder" portion 2v2 is preferably-made ofv a piece o'f solid barfstocl which at`its-inner end yissquared oir for ready attachment tol the'tool Vshank 2B while the other endfthereof Yis machined out to form va' recess or;V socket 26 into which Athe similarly shaped inner end ofthe cutting bit portion'23 is adapted to be seated. Y `The cutting bit 23 is preferably constructed of; one ofthe highspeed duty compositions-*such as tungsten carbide of the' type known as fBarboloymor the like vand issecureol` to the' bit holder/portion'22 by copperbrazingjfthe recess 23 of the holder'22 and sirnilarlyshaped inner end of the bit23 being provided Yfor the purpose of Ifroviding a greater surface-'area `of Abrazedv `j oints toinns'ure amore:intirnateuniting ofthe parts for Yithstanding `the torquek stresses placed i upon the drill1when-`in^Servicer` llhe bit 23 and holder 22 are provided with a longitudinally'7 'extending hole" 2lL which" forr'ns a conduit' for oil under: pressure' and which is 'in communication with l a conduitfZiif` formed `in the shankportionZ ofthe drill'.` The bit'portion'23 Yofv their drill has its outer end groundito provide a'spec'ial type 'of a' cutting edge 2'9fvsuc'h'as usually employed for gunbarrel drillsandformed byone side of the nnte 3o pro-Imaam the apporti@ 23, The -flute 30j is arranged' in*Y"longitudinal align-l nient with a similar flute :ie-r p'mrnjldedein the holder portion 22' and which'is sirnilarlyaligned with* the similar IiuteZ formed in the shank por; nonzu oftneidrring In "ojrdertoA insure eicient cuttings action of the" tool bitV and, to insure ample lateral" support Vthereof to prevent'sidewisedrifting ofthe cut'- ting" end 'ofthe VYdrilljthe tool'bit portion'ispro vided on that V4side of" the; ute'SG, "the'end of which forms the cutting edgerZSL'witha'land 32 tnefwldth of whiehisof the @merci abouti-2- of anj-inch whilethe opposite side lof the" drill adjacent the jsi'dev` edgeV 33 of "the `flute 33 'is pro. vided'with a wider land 34 and that portion'of the tool bit diametrically opposite from the nnte 30j vis provided with eilanden a 'rneftnreelandsjs g, 34fand135"are the .fulldiainete'rf'of 'the toolbit and ef th-hole to te driuediwhiie those-poni wall of the tube employedforthese'drill,shan

Y @beigelegt new.

of the tool bit between the land 32 and 35 and 34 and 35 respectively are relieved as indicated at 36 and 3l to reduce the frictional contact area between the drill and the hole drilled thereby. The bit holderY portion 22 is also provided with lands and relieved portions similar to those provided in the cutting bit 23.

After the parts 20, 22 and 23 have been united together as indicated in Fig. 3, the ash formed bythe brazing 25 is ground oil? and the parts are thenfpref-erably subjected to a plating or nitriding operation, but preferably chrome plating, which serves'to form a continuous outer ksurface along the three assembled portions and to completely cover the joints between the respective parts formed by the brazing of the bit 23 to theholder 22 and of the latter to the shank 2e, the plated coating being built up to a point a 'few thousandth'sabove the desired nished outer diameter and then being ground down to the exact dimension, the outer plated coating of the parts Vas indicatedlv by the refer'encecharacter 38 being shown in' va somewhat exaggerated form nFgA- ai Y Y In contradistinction to the methods hereto# fore employed for'th'e boring of rifle barrels and in' which the drill was' held in hori'zoiitalposition,V I have found that much better results and a higherrateof production can be procured by holding the drill stationary in any suitable hold"- er vor chuck,v as indicated bythe reference char acter 3.9 in Fig.' l, While the rifle barrel 4S: 'to be' drilled orb'ored 'isrotated rapidly and'fed downwardly' over thedrill' as l'indicated by the arrowinFig.`1.

`In the drilling of the rifle barrels it has always beenv the 'practice to supply oil or other suitable cutting fluid under extremely high pressurethrough the central tubular'part l28 of the drin lShank and' connecting conduit 21 under' Yvery high pressure and to rely upon the pressure of the cuttingy fluid to carry awaythe chips and wash them through theflute'fil to vthe"ba-cl;V edd of the driuff-By mounting `vthe drin' in a vertical positi'onand feeding the gun barreld downwardly VonV to the drill as Yindicated in'Fig. l2 the force of gravity carries the 'chip's'downwardl'y alOngWth the"t fluid 'td be ejectd'jttl'e bcli end of the drill and it is not;'tlf're'refore; ne'ci essa'ry' withv adrillas disclosed and'u'sed' in Eaccordance with-the presentinvention, fto resort to such'-Y extremely higli'ipressures' "for the"c1t4- tingrnuidx' I' 'f f f' As hereinbeiore explained the shank portion 2l] of theeuttin'g anus 'heretofore 'empioy'eafortn drilling'of gun 'barrels liavefa y beerrfc'onl Structed 'of arpie'eefof, tube-st o of which nasrbeen rolled; er pressednwdly "toi ferm me c1earancel nete se;tneefeeftilefwas 'lf' the v s' Moreoveras" the flute portion' wasy forrned'veni; tireiy'b'y A 'reumgendf drawing; tneffi'w "or tri metal produced-a very appreciable "curvature-of the rnetal'fofrthve 'tubeinthose portio'sf't "'eieof immediateiyiedjaeen" the "clearance Vcute wenn resulted 1 in* a* cqirespondmg*aporecitle decrease in diameter offtliesnanl'be1-ow 'the Ede; si'red lnished iln'ension attlfezplaoe1 twhe l`the full dimension offthe drill'y Wasrno'st neededfor a'very decidedfliniitationin the thiikness o lateral supportt preventenfnngend Migrating;

' limi-@Cree 'the ffmlrflaiieh 'Of shank.. inw the desiredcongurationA to' providdthe chipf c af: an@ @die by bending androiiolg the me" 2525,535 ness or the 'wan tute tnatcuid be used for 'drin shanks fabricated in the manner heretofore em" ployed, resulted in a final product which had veryV slighty resistance tothe torque which the drill was called upon to resist in performing its intendedcutting function.

In order to avoid the above' mentioned unde-v sirable featuresand to'providea contour ofthe drillv shank in which the shank would be of the desired full diameter closely adjacentto the chip clearance flute and so that the shank can be constructed of muchiheavier tubing better able to withstand the torque stresses; the Vdrill shank of the present invention" is constructedin the manner indicated Vby the" seriesof views Figs. 6. to l1 of the drawings.` A

In fabricating the 'shank Vportion a relatively thick walledstube ZUJ--aV as shown inV Fig, 6k is employed. This tube then has4 a Vportionveof oneV side wall thereof cut away by any suitable means such; for example, as a' form milling cutter to provide the`converging side wall portionsr or flats Eiland to reduce the tubelalong its entire length to the `form shown in Fig.` 'l of the drawings.V

This operation, it will'jbe seen, reduces the wall El of thetubeadjacent the flats 50 particularly at the'central point thereof lto a thickness approximately one-half of the original thicknessof Ythe tube walk The tube is'next subjected to a rolling operationwhich presses the thin wall portion 5i `of the tube inwardly towards the center thereof and causes'the flats 50 to be merged into a single flat surface 52 which bears the relation of a chord to the original circularrcross .section of the tube. i

The next step in the formation of the shank is to subject' the flat wall 52 Vto a further rolling operation, thereby forcing the thin' wall 5| fur-V ther towardsthe centerline ofthe tube and to` transform the flat Wall 5.2 into the 're-entrant'arcuate or convex wall 53v and tobring the tube tofthe form shown in`Fig. il of,` the drawings. The tube is then 'subjected'to another rolling operation which forces the thin wall 5| thereof slightly past the center of the tube and towards the opposite thicker'wall and to form a pair of fiat-s 54 forming a re-entrant angle and leaving the tube in the condition shown in Fig. l0 of the drawings. e

The next step is to subject the tube to still a further rolling operation in which the wall 5| is pressed still farther towards the opposite side wall and to form the chip clearance flute 24 inV the shank 20, this iiute having side wall portions 25J-a and 33-a which correspond with the similar side walls 29 and 30 of the toolbit portion 23. As the tube leaves the rollers which press the wall 5| downwardly to the position shown in Fig. 11, the tube then is subjected to the action of a group or finishing rolls which engage the outer arcuate surface ofthe tube adjacent the edges of the flute walls 29-a and 33-a, thereby to insure that substantially the entire outer curved surfaces of the tube will be of the required diameter and free from any protuberances; the tube in its nal condition being as shown in Fig. 1l in which the original-cylindrical bore has been. converted from its circular cross sectional form into a somewhat crescent shape which forms the conduit 28 by means of which cutting fluid under end of the shank by a simple butt welding o1' brazing operation as hereinbefore described.

As'will be seen from an inspection of the cross sectional View ofFg. 11 the shank 2B in its final form has the major portion of its arcuate side wall portions 60 of a thickness substantially twice that of the thickness of theside wall portion 5| at the flute'p'ortion of the shank, the major portion of 'the torque reaction being transmitted to the shank in the direction of the arrow A in Fig. 11, is therefore, communicated directly to the thicker sidewall 60 with the'result that a drill providedwith a shank of the type shown in the drawings offers very effective resistance to the torque stresses. t v v' It will also be seen from an inspection of Fig. l1 thatthe opening formed by the crescent shaped conduit 28 Aforms but aminor portion of the cross sectional area of the shank-the major portion thereof being formed of the solid metal of the tube walls. .Due to the greatly reduced area to .the conduit 28 over devices of the type heretofore vAnother feature'ofV great importance in a tool;

shank constructed in accordance with the present invention is that due to the method Of fabricatingthe shank the outer curved surface thereof is maintained at substantially the full diameter up to a point very close to the side walls 29-1-a and 33-a of the flute portion 24 and consequently the shank is of the full dimension of the hole to be' drilled for very much more than the semi-circumference of its circular cross section. This insures that the shank will be in lateral contacting engagement with the bore of the hole to be Vdrilled'closely adjacent to the flute portions thereof at which point-*the need for lateral support is greatest. 1

In using the drill of the present invention it is, ashereinbefore pointed out, preferably supported in a vertical position as indicated in Fig. l of the drawings. The bit portion of the drill hav- 'ing been formed as hereinbefore described and as illustrated in Figs. 2 and 3 of thedrawings and the drill preferably being provided with a high speed duty type of cutting bit or tip, the rifle barrel 40 may be rotated at a speed of rotation many times greater than that employed with the drills as hereinbefore constructed, and consequently it is not necessary in order to get remarkable increased production, to use a heavy feed that would place heavy torque stresses upon the drill. As the chips are cut away by the cutting edges of the tool from the gun barrel, such chips will tend to drop by the force of gravity to the fluted portion thereof and prevent any undesirable accumulation of chips either adjacent the cutting edge of the drill or along the shank portions thereof. However, as an added precaution against chip accumulation, oil under pressure is supplied from a suitable source of fluid pressure through the crescent shaped conduit 28 of the shank 20 to pass therefrom to the hole or conduit 2l provided in the bit holder 22 and bit 23 to be delivered immediately adjacent the cutting edges e of the tool and to wash the chips as they are cut pressure is supplied to the cutting edge of the from the stock backwardly through the fluted portion of the drill.

It will be noted that the thicker curved walls of the shank form a brace for substantially more than half the sides of the flute and which brace 1 extends substantially along the line of the twisttcrciie'reeietent censtrnctien.;

Icieihifr L 1- A, tccl ci the character described ccrnbris# irggfa iubiilerelidnk. dertien Vpreyided with. 'a creleceni sheeedcendnit, d toeren. holder d hifhebeed cntine tcci bit., eachjhayine cen-J enineritwith .seid crescent.. shaped t) Sei tdci ebenki .teel bit he and todi.'

blt. beierrcyided' w. a ccntindonecnter ccetr' between inecrtcrdiie icrcee. .tbiis providing e stiffer, morevv ine' ccyeiiilne. 'the bit holder eindl tool biti,

.2- in, 'n tccl, ci the eharecterdescribed e. tccl. ehenli hei/ine e lcneitndinally extending chip Qleerdncefldie end e substantially centred cree-u cent shaped fluid pressure conduit, the thickness ci tbc Side wall ci Said shnnls alone the arcuate portieri thereof, and ier Substantially there than hel-f. the crees. sectional. circliinierelnee, being ab: lircxirnetely twiceihe thickness ci the Sidefweill et .the` central part ci Seid chipclearance nnte.

3. nv tool of the characterdesc'ribed haring a cutting bit portion end a--tnbuler shank with( e. longitudinally extending chip. clear` c@ Quite brcyided therein, thel thicknese ci the of said shank adjacent the central part of said flute beine. approximately One-heli the thickness ci the cbbccifte side.- We'll ci. Seid ehenh, Seid;

Shenlr beine fcrrned with e vctrlindricdl. portieri..

the, circumferential length ciwnich.. ie ceiibetdne tielly grenier infinite Senn-.circliniierenee- I 4.. 'A tool of the character describedY hav-ing a cutting nerticfn end e. tubular cheek with e len eitndinellyertendine.- chi-p .clearanceiinte end Sibstdntielly' central. crescent shaped; fluid. bres.: eiire cciidiiit brfcrided therein Seti/d Yehnnlsherel ineY e. thickened; b crticn. Side been. ne the ccn're'x side 0f said; creecentehenedccn end eriendine ebbetnntielly irfiihe'l directicn. di they reecticn tcJ the tcrdiie iQrceS. te., which the shanlc portion of said tool is subjeciied and bracing ghe; iii-e101" Dertien. ci the side,- cieeid finte that.; cdrrechcbdb; te the. .ttineedee ci the. bit.; the tcidiie.idrceei vddid nhenkitgecl Side wall f ting rela A ioei of the. cherdcter described comprising.' n cutting. bit eerbied. abit helder portion and a 's .nk portieri. s ecnredtcgether in abrite enshib te. icrm, n n integral structure and. having e; thin outer ceatine extending along the'outer periphery of each oi sad'portions to ll the ereyiees etthepcints. ci union. 'ci Seid editions withjeech, other end thereby ic. formV a smcctneontindodsiend uninterrupted surfaceit?. A drilljoi the character described compris.-

' ine d tubularl Shank. portion, a tcclbit helder egiptrernity of said tool bit; holder member form- Ynreylde. clearance spaces. Y K '75; A drill, of the character described comprisfing a tuhiilar'shank portion, a tool bit', holderV rneinber and' e tc'cl bit,.member. each of Seid members and Said tubular Shank( beine provided yiih a' ccntinueus. longitudinally extending chip clearance, initie and each 0f Seid members. being provi-ded with a land extending' along the outer periphery ci said drill adidcent to eech cuter edge.. di seid finteend ei third land extending vdiene seid. cuter peribheryintermediete the nrst .20; 'daily the full diameter of the hole to be drilled meiiticned two. lends., Seid lands heine` Subsidieby said drill and vthe outerperiphery of said members being relieved' between said lands to member and e tccl bit member, each of seid members and said tubular shank being provided with af continuous. lllgitudnally ,exteilding` vchip clearance finte, one side YQnly'of said flute at the ing @he entire cutting edge of said drill and said tQQl; btmernber and tool bit holder member be- Y ing provided along the periphery of thedrill i., adjacent the cutting edge side of said ute with i e. narrow land and seidperiphery being `provided with, a'rwide land adjacentio the other edge of said flute andy said;` drill being provided with a third. land extending along'the. periphery ci Seid -A members. between. .saidnarrow land and seid Wide lend endthe remainder of the periphery of seid members, between said. lands being relieved to forni clearance., Spaces,

Y Y Y ALBERT J- NORDBERG-

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