us2311591 - lathe step threading attachment, 1941

7/27/2019 US2311591 - Lathe Step Threading Attachment, 1941

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Feb. 16, 1943.. F. GROENE ET AL,311,591STEP THREADING MECHANISM

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INVENTORS.WILLIAM F. QROESEBY Ross M .BACON

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Feb. 16, 1943. 2,311,59110 SheetsSheet 8

W. F. GROENE ET ALSTEP THREADING MECHANISM

Filed April 7, 1941

INVENTORS.WILLIAM F . G c R O E N ER O S S M. BA CO NBY

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INVENTORS.V J LLIAM F. qROENEBY ROSS M.33ACON

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2,311,59110 SheetsSheet 9


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Patented Feb. 16, 1943 2 , 3 1 1 , 5 9 1

UNITED STATES PATENT OFFICE2,311,591

STEP THREADING MECHANISMWilliam F. Groene and Ross M. Bacon, Cincinnati,Ohio, assignors to The R. K. Le Blond MachineTool Company, Cincinnati, Ohio, a corporationof Delaware

Application April 7, 1941, Serial No. 387,2489 Claims. (Cl. 10-101)

This invention pertains to step threadingmechanism for use in conjunction with lathesand is particularly related to a step threadingattachment for engine lathe which is adaptedto machining or chasing both external and in-ternal stepped threads on work such, for exam-ple, as breach blocks and breach rings for guns.More particularly this invention pertains to im-provements in step threading mechanism where-by the production of such apparatus is greatlyincreased and wherein is combined ease and ac-curacy of operation with greatly minimizedeffort on the part of the operator in controllingthe apparatus.One of the chief objects of this invention isto provide automatic power operated feed andrapid traverse mechanism for actuating the chas-ing tool in feed and rapid traverse movementsin such a way that the chasing tool is alwaysmaintained in proper position relative to thethreads being chased as it is successively passedover the threads at increasing depths of cut.Another object of this invention is to provide,in conjunction with such actuating mechanismfor the chasing tool, means for automaticallyand accurately stopping the work spindle inproper position at the end of each chasing cutso that the chasing tool may be fed up closelyto a shoulder at the end of the thread or stopit in a drilled hole or other clearance hole atthe end of the chasing cut. It is a further ob-ject in connection with this apparatus that thisautomatic stopping takes place without effortand skill upon the part of the operator whileat the same time providing automatic and muchmore rapid means for effecting the proper stop-ping of the chasing tool and work spindle atthe end of each chasing cut.Another object is to provide a unique tool barsupport having accurate adjustment and move-ment parallel with the direction of feeding ofthe chasing tool relative to these threads to becut, so as to effect very accurate setting of thechasing tool in proper lead position longitudi-nally of the work being chased.Another object of this invention is to set thecutting tool a considerable distance above thecenter line of the lathe, the purpose for thisbeing to provide more jumping clearance for thetool to clear the threads while chasing. Withthis arrangement, the tool clearance is increasedapproximately 50 percent greater than by set-ting the tool in the conventional manner on thecenter line of the lathe. As a result, the spindlespeed of the machine can be increased to there-

by greatly increase the productive output of themachine.A further object is also to provide means foraccurately positioning and limiting the cross5 movement of the step threading attachment whenrapidly removing the cutting tool radially awayfrom the work as it is traversed back to a newstarting position.And again another feature is to provide a1 0 unique tool bar, carrying the chasing tool, whichmay be readily adapted for both internal or ex-ternal positioning of the tool for internal andexternal step threading.Further features and advantages of this in-1 5 vention will appear from the detailed descriptionof the drawings in which:Figure I is a front elevational view of a modi-fied engine lathe incorporating the step thread-ing mechanism of this invention.20 Figure II is a plan view of the apparatusshown in Figure I.Figure III is a left hand end elevation of themachine of Figures I and II particularly show-ing the driving gearing for the feed and rapid25 traverse screw for actuating the step threadingattachment longitudinally of the lathe bed.Figure IV is a vertical transverse sectionthrough the machine and step threading attach-ment on the line IVIV of Figures I, II, V, VI,30 and VIII.Figure V is a horizontal fragmentary sectional

view through the attachment on the line VVof Figures I, IV, and VI.Figure VI is a vertical sectional view from35 the rear of the step threading attachment shownon the line VIVI of Figures II, IV, and VII.Figure VII is a fragmentary sectional view onthe line VIIVII of Figures II, V, and VIII, par-ticularly showing the cross stop mechanism for40 controlling the radial movement of the attach-ment to and from the work by the cross feedhand wheel operating mechanism.Figure VIII is a fragmentary horizontal sec-tion through the reciprocating tool slide shown45 on the line VIIIVIII of Figure VI.Figure IX is a fragmentary section showing the

actuating gear cam indicated by the line IXIXin Figures IV and V.Figure X is a fragmentary view of the actuat-50 ing lug and associated plunger for effecting therapid jumping of the cutting tool for effectingthe step threading operation.Figure XI is a fragmentary diagrammatic viewof the relationship of the step threading tool and55 the work at the beginning of the chasing of the


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2,311,5131smaller diameter thread, in chasing an externalstep thread.Figure XII is a view similar to that of FigureXI but showing the position of work and tool atthe completion of the cutting of the smaller di-ameter thread and at the movement the tool isto be stepped outwardly for the larger diameterthread.Figure XIII is a view similar to Figures XI andXII but showing the position of the tool at theinstant it has been fully stepped for movementoutwardly to begin the cutting of the larger diam-eter thread.Figure XIV shows the relationship of work andtools in cutting an internal step thread with thetool positioned at the beginning of the cutting ofthe larger diameter internal thread.Figure XV is a view similar to that of FigureXIV but showing the cutting tool at the comple-tion of the chasing of the larger diameter inter-nal thread.

Figure XVI is a view similar to that of FiguresXIV and XV but showing the cutting tool afterit has been moved or stepped outwardly and atthe beginning of the cutting of the smaller diam-eter internal thread.This step threading mechanism is shown ap-plied to a typical engine lathe having a bed 1upon which is mounted the usual headstock 2having transmission mechanism for rotating awork spindle 3 journaled in the headstock 2.This headstock transmission is driven by a maindrive motor 4 which drives, through suitablebelted means, the combined brake and clutch pul-ley 5 of the type for example as shown in Pat-ent #1,528,973, dated March 10, 1925, connectedto the input of the headstock transmission in theconventional manner. On the work spindle 3 isappropriately carried the work face plate 6which has appropriate chucking mechanism 7 forcarrying a work piece 3 to be step threaded.On the ways 0 and 10 of the bed I is slidablymounted the lathe carriage II which is arrangedto be fed along the bed on the ways by meansof the lead and rapid traversing screw 12 whichoperates in a threaded nut 13 rigidly fixed to theunderside of the front portion of the carriage 1 I.This screw is provided in this particular instancewith appropriate threads I 2a having the properlead for its rate of rotation to effect the propermovement of the carriage with relation to thethreads 8a and 8b to be cut on the work piece 8.The left hand end of this lead screw 12, Figure I,is journaled in an appropriate bearing 14 againstaxial movement therein and has fixed on its outerend a driving pulley 15 which is connected bysuitable belts 16 to the pulley 17 of the rapidtraverse motor 13 mounted on the bed I of thelathe. Power from the headstock transmissionis connected or disconnected to the lead screw 12through the medium of a single tooth clutch 19appropriately slidably mounted on the shaft 20journaled in an appropriate bearing 21 carried onthe bed I of the lathe. This shaft 20 is driventhrough appropriate change gears 22, 23, and 24from the output shaft 25 of the headstock trans-mission so that the shaft 20 is at all times posi-tively rotated in direct relationship to the rota-tion of the work spindle. By use of the single jawclutch 19, power from the shaft 20 may be con-nected or disconnected to the lead screw 12 inalways the same predetermined relative position,so that no matter when the clutch is disengagedfrom the lead screw 12, reengagement will alwayseffect the proper orientation of the rotary posi-

tion of the lead screw with respect to the spindlerotation of the headstock, thereby keeping thethreaded portion of the work on the work spindlein prompt relationship to the lead screw and the.5 longitudinal position of the carriage on the lathebed. The motor 18 is at all times belted to thelead screw 12 and rotates slowly therewith underthe influence of driving power from the shaft 20when clutch 19 is engaged with the lead screw10 12, the motor 18 only being energized in one di-rection or the other for rapid rotation of the leadscrew 12 when the clutch 19 is disengaged fromthe lead screw. Energizing of the rapid traversemotor 18 for rotation in either direction may be15 electrically effected by the usual electrical con-trol means through the medium of operating the"traverse left" push button 26 or the "traverseright" push .button 27 located on the front of themachine as shown in Figure I. Operation of the90 single tooth clutch 19 is effected by means of thebell crank lever 28 mounted on a suitable shaft29 fixed in the bed I of the machine and whichlever has appropriate means operating in the an-nular groove 39 of the clutch 19 and has its other95 end suitably connected to a solenoid 31 wherebyelectrical operation of this solenoid effects en-gagement or disengagement of the clutch 19 withthe lead screw 12.The stopping and starting of the work spindle

30 3 is controlled by appropriately operating thecombined brake and clutch pulley 5 through thecontrol rod 32 and the yoke 33 on the spindle con-trol rock shaft 34 in the usual manner as shownfor example, in Patent #1,528,973, dated March35 10, 1925, either by rocking the shaft 34 throughthe medium of the manual control handle 35,Figure II, or by means of the control solenoids36 and 37 mounted on the bracket 38 on the rearof the headstock 2. When the solenoid 36 is en-40 ergized it releases the clutch and causes the braketo operate in the pulley 5 thereby substantiallyinstantly stopping rotation of the work spindle 3.When the solenoid 37 is energized it moves theshifter rod 32 to the left, Figure II, effecting en-

45 gagement of the clutch and disengagement ofthe brake in the pulley 5 thereby connecting pow-er from the motor 4 to the headstock transmis-sion to effect rotation of the work spindle 3.Solenoid 35 is rendered operative by contacting50 the spindle stop push button 39 while the solenoid37 is rendered operative by actuating the spindlestart push button 49, as seen in Figure I. A mo-mentary contact button 4I is provided for effect-ing intermittent operation of the solenoid 37 for

55 "inching" or slowly bringing the spindle inter-mittently around to desirable positions for toolsetting.The attachment itself comprises a housing 43,Figure IV, which is slidably mounted on appro-60 priate dove tail guide ways 44 formed on the car-riage I I to permit cross travel movement of the

attachment to and from the axis of rotation 45of the work to be step threaded. Cross travelmovement of the housing 43 is effected through65 the medium of the nut 46 appropriately fixed onthe housing 43 in which operates the usual lathecross feed screw 47 journaled against axial move-ment in a suitable bearing 48 carried on the frontof the carriage 11, the cross feed screw 47 being70 manually rotatable by means of a suitable crossfeed hand wheel 49.Referring particularly to Figure VII, limitationof this cross travel of the housing 43 is accuratelyeffected by means of the automatic cross stop'75 mechanism shown in this figure. This apparatus


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4,311,591mounted in it a sliding splined shaft 96 which isjournaled against axial movement in suitablebearings 97 and 98 in the housing 43, so that thisshaft 96 may at all times be driven from theheadstock transmission for any cross travel po-sition of the housing 43 on the carriage 11 of thelathe. On the front end of the shaft 96 is pro-vided a pinion 99 which is arranged to drive thegear 84 having the cam 83. All of this transmis-sion constituting the bevel gears 93 and 94 andthe pinion 99 are so arranged, in this particularinstance, that the gear 84 and cam 83 rotates inexact synchronous rotation with that of the workspindle in such a way that the gear 84 makesfour revolutions to one revolution of the workspindle 3, it being obvious that there are four setsof step threads on this particular piece of work.Other different types and numbers of stepthreads obviously would require other ratios ofrotation of the gear 84 to the work spindle ro-tation.One of the unique features of this inventionis the setting of the cutting edge 100 of the cut-ting tool 64 a relatively large amount above thehorizontal center line 101 of the lathe in orderto provide more jumping clearance for the toolto clear the thread while chasing. This is bestseen by particular reference to Figures XII andXIII. In the more conventional arrangement thecutting edge 100 of the tool is arranged to re-ciprocate in a direction indicated by the line 102,which passes through the axis of rotation 45 ofthe work and is substantially a radius from thecenter to the cutting edge of the tool. In appli-cant's case however, the reciprocation of the tooltakes place in a line 103 which lies in a horizontaldirection considerably above a horizontal centerline 101 of the lathe so that the line of recipro-cation 103 is not a radius but passes considerablyabove the center of rotation 45 of the work. Inthis way, greater jumping clearance is providedfor the cutting edge 100 of the tool as it can beseen in the old or former method comparingFigures XII and XIII, that the tool is jumpingfrom the smaller diameter thread to the largerdiameter thread, which moves out the radius 102to the position 104 whereas in the applicant'snewer mode of operation, the cutting edge 100 ofthe tool moves along the line 103 out to the posi-tion 105. Noting particularly Figure XIII, thepoint 104 in the older method would be partlyentered into the thread portion 8b, which wouldprevent moving the tool out along this slant ofapproach with the high speed of rotation of thework as is possible in this case, as it can be seenthat the point 105 still does not contact the nextthread 8b to be cut even though rotating at thisrelatively more rapid rate. It has thus been foundthat with this new arrangement that approxi-mately fifty percent greater tool clearance is pro-vided with the consequence increase spindlespeed which can be obtained by this unique ar-rangement.The operation of this step threading apparatusis substantially as follows:

The main drive motor 4 may be started orstopped at any time from the push button sta-tion 106 having the start push button 107 and thestop push button 108. Once the main drive motor4 is started by operating the push button 107, itwill continue to run at a relative high speed, inthis instance 850 R. P. M. or at a relatively lowspeed, in this instance 200 R. P. M. The twospeeds of the main drive motor are controlled bythe relative position of the carriage I I longitudi-

nally of the bed i of the machine. The twospeeds of the motor are electrically controlled bymeans of the main drive feed control limit switch109 located on the front of the headstock as best3 seen in Figure I, which is actuated through asuitable actuating plunger 110 carried in abracket 111 on the ways 9 of the bed I and whichis engaged by the surface 112 of the carriage 11so that this switch 109 will be actuated while the10 carriage is moved longitudinally to the left, asseen in this Figure I. The bracket 111 is so posi-tioned on the ways 9 of the bed that the carriage

will engage its plunger 110 in such a way thatlimit switch 109 will be actuated at the time when13 the carriage has just about moved to the end ofthe chasing cut to be made. Whereupon themotor will be reduced from its high to its rela-tively low speed of rotation. Thus the workspindle 3 is rotating at relatively slow speeds at00 the time of final cutting on the thread to bechased, the purpose of which being to facilitatemore accurate and rapid stopping of the workspindle when the cutting tool has reached theexact end of the thread to be chased., 5 After the main drive motor has been started,the spindle does not rotate until the spindle startbutton a n has been pressed which energizes sole-noid 37 as described, operating the clutch in thedriving pulley 5 to connect driving power from

3 0 the motors to the pulley and to the headstocktransmission to the work spindle 3. The toolcarriage which in this arrangement initiallystarts at the right and feeds toward the left inchasing threads on this particular work piece, is

:33 fed from power from the main drive motorthrough the output shaft 25 of the headstocktransmission and thus through the change gears22, 23, and 24, and its feed screw 12 as described.At this time the single tooth clutch 19, Figure I, is:0 normally held into engagement with the feedscrew 12 by its spring 19a so that the carriage isfed simultaneously with the rotation .of the workspindle 3 from the headstock transmission, themovement of the carriage and the work spindletaking place in synchronous movement. Also the) drive to the cam 83 of the step threading attach-ment is driven through the various splined shaftsand bevel gearing, as pointed out in Figures IVand VI in proper synchronous rotation with the

;0 work spindle so as to effect the proper jumpingposition for the cutting tool of the attachmentduring rotation of the work spindle.As the carriage feeds along to the left, as shownin Figure I the limit switch I0 .9 is actuated as de-scribed near the end of the thread to be chased so5 5 that at the last few revolutions of the work piecebeing chased, the work spindle will be rotated atrelatively slow speed in this particular instanceat about 1 R. P. M.

60 On the headstock 2 is mounted a bracket 113which carries a positioning limit switch 114 whichlimit switch is arranged when it is actuated toenergize solenoid 36 to thereby disengage thedriving power from the main drive motor 4 to

63 the pulley 5 and immediately effects the opera-tion of the brake in said pulley to arrest rotationof the headstock transmission and the associateddrive to the step threading attachment and thecarriage 1 1. This limit switch 114 is actuated by70 a suitable dog 115 carried on the face 6a of theface plate '6 so that it is actuated for each revo-lution of the work spindle 3 and the face platemounted thereon. However, this limit switch 114is not effected though actuated until the limit75 switch 109 has first been actuated by movement


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2,311,591of the carriage 1 1 to substantially the end of thechasing movement. The function of this switchtherefore is that after the limit switch 10 9 hasbeen actuated by movement of the carriage 11thus bringing the motor to the relatively slowspeed of rotation, the limit switch 114 will thenbecome operative just after the switch 10 9 hasbecome operative whereupon the headstocktransmission will be stopped in driving action andinstantly braked against further rotation by op-eration of solenoid 36 through the medium of thecombined brake and clutch in the pulley 5, aspointed out. Furthermore by properly settingthe trip dog 11 5 for the limit switch 11 4 sub-stantially accurate stopping of the work spindlemay be accomplished, as it is rotated at suchrelatively low speed that the rapid operation ofthe solenoid 35 effects the substantial instantbreaking or stopping of the work spindle in a pre-determined desirable position necessary for therunning out of the thread into a drill hole orother movement of the cutting tool up against ashoulder on the work.After the limit switch 11 4 has been tripped andthe work spindle brought to accurate stoppedposition, the hand wheel 49 of the cross feed forthe housing 43 of the step threading attachmentis backed off so as to move the attachment outaway from the work bringing the nut 54 , FigureVII, against the bevel gear housing 52, stoppingthe unit at a proper relieved position. The"traverse right" push button 21 , Figure I, is thenpressed whereupon the solenoid 31 is energizedwhich withdraws the single jaw clutch 19. Theengaging of the clutch 19 through the medium ofits lever arm 23 causes this arm 23 to engage alimit switch 112 which permits transmission ofelectrical power to the rapid traverse motor 18,so that when the button 21 is pressed the motor18 is actuated for rotating the screw 12 in such away as to rapidly rotate it for returning the car-riage 11 to the right shown in Figure I Immedi-ately releasing the push button 27 causes themotor 13 to substantially instantly stop bydynamic braking so as to arrest the carriagein position for another pass over the thread tobe step chased. Pressing the control push button26 can effect the "reverse traverse" of the motor18 and the reverse movement in the carriage 11and the disengagement of the clutch 19 throughthe solenoid 31 so that it is possible to rapidtraverse the carriage more accurately up to posi-tion at the beginning of the thread in traversingthe carriage to the left. As soon as either of thepush buttons 21 or 26 have been released theclutch 19 again automatically engages in the cor-rect position with the lead screw 1 2 through themedium of its automatic operating spring 19a.The cycle of operation may then be repeated byagain pressing the spindle start button 40 , thecutting tool 61 again going through the samecycle of operation with the slow down of thespindle near the end of the thread being chasedand the final stopping of the spindle stopping byactuation of the limit switch 11 4 in proper accu-rate indexed position relative to the cutting tool,whereupon the "reverse traverse" button 27 isagain pressed to return the tool after it has beenwithdrawn by the handwheel 49 to relieve it fromthe thread and it is traversed back to the initialstarting position again.Having thus fully set forth and described ourinvention, what we claim as new and desire tosecure by United States Letters Patent is:1. In a step threading mechanism, a rotatable

work spindle, power means for rotating said workspindle, means for connecting or disconnectingsaid power means from said work spindle and forbraking said work spindle against rotation when5 said power means is disconnected therefrom, atool feeding device having feeding movementrelative to said work spindle, means for feedingsaid tool carrier in a predetermined relationshipto the rate of rotation of said work spindle, a

10 tool on said tool carrier, means for reciprocatingsaid cutting tool in step threading motion in syn-chronism with the rotation of said work spindle,means rendered effective by the movement of saidtool carrier in feeding movement for changing the15 rate of speed of said power means for rotatingsaid work spindle, and means operable by the ro-tation of said work spindle for rendering saidspindle braking device operative for stopping saidwork spindle in a predetermined indexed position20 relative to said cutting tool.2. In a step threading mechanism, a rotatable

work spindle, power means for driving said workspindle, means for connecting or disconnectingsaid power means from the work spindle and for25 braking said work spindle against rotation whensaid power means is disconnected therefrom, acutting tool, and means for feeding said cuttingtool relative to a work piece mounted on saidwork spindle, said feeding means being arranged30 to move said tool carrier at a predetermined rateof travel relative to the rotation of said workspindle, means for reciprocating said cutting toolin step threading movement in synchronism withthe rotation of said work spindle, means for mov-35 ing said tool carrier at a rapid rate of travel rela-tive to said work spindle, means for effecting dif-ferent rates of rotation of said work spindle bysaid power driving means, and means operable bythe rotation of said work spindle for stopping said40 work spindle in a predetermined indexed positionrelative to said cutting tool.

3. In a step threading mechanism, a rotatablework spindle, power means for rotating said workspindle, means for connecting or disconnecting45said power means from said work spindle and forbraking said work spindle against rotation whensaid power means is disconnected from said workspindle, a tool carrier, means for feeding said toolcarrier relative to said work spindle, a cutting tool50 on said tool carrier, means for reciprocating saidcutting tool in step threading movement in syn-chronism with rotation of said work spindle,means rendered effective by the rotation of saidwork spindle at the instant said power means is55 disconnected therefrom for rendering said brak-ing means for said work spindle effective to stopit in a predetermined rotary position.

4. In a step threading mechanism, a rotatablework spindle, a tool feeding carriage movable60 relative to said work spindle, power means forrotating said work spindle at a plurality of dif-ferent speeds, means operable by the movementof said carriage to effect said different rates ofspeeds for said power means, means for connect-65 ing or disconnecting said power means from saidwork spindle and for braking said work spindleagainst rotation when said power means is dis-connected from said spindle, a cutting tool mount-ed on said carriage, means for reciprocating said70 cutting tool in step threading movement relativeto a work piece in said work spindle, means forfeeding said carriage relative to said work spindlein a predetermined rate relative to the rotationof said work spindle, and means operable by the75 rotation of said work spindle, effective when said


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6,311,591carriage has moved to effect a change of speed Insaid power means, for operating said brakingmeans for said work spindle to bring said workspindle to a stop in a predetermined circumfer-entially oriented position.5. In a step threading mechanism, a rotatablework spindle, a tool feeding carriage movablerelative to said work spindle, means for feedingsaid carriage at a predetermined rate of move-ment relative to the rotation of said work spin-dle, a cutting tool mounted on said carriage,means for reciprocating said cutting tool in stepthreading movement in synchronism with therotation of said work spindle, power means fordriving said work spindle at a relatively highspeed and at a relatively low speed, means forrendering said high and low speed effective bythe movement of said carriage, means for con-necting or disconnecting said power means fromsaid work spindle and for braking said workspindle against rotation when said power meansis disconnected therefrom, and means operableby the rotation of said work spindle, when saidcarriage has moved to a position to effect lowspeed operation of said power means, for ren-dering said braking means for said work spindleeffective to stop said work spindle at a prede-termined position relative to said cutting toolon said carriage.

6. In a step threading attachment for lathe,a tool feeding carriage movable relative to awork piece to be step threaded in said lathe, areciprocatable slide movable in synchronized stepthreading movement relative to work piece rota-tion in said lathe, a cylindrical tool bar mountedin said reciprocating slide with its axis parallelto the axis of rotation of said lathe, means foraccurately adjusting said cylindrical tool barparallel to the axis of rotation of said lathe,means for positioning said tool bar around itscircumference in two positions, one position forinternal threading operations and one positionfor external threading operations, and a cuttingtool mounted in the outer end of said tool barfor operation on a work piece in said lathe, andmeans for mounting said cutting tool in saidtool bar by means of the ground surface ofsharpening of said tool so as to accurately lo-cate said cutting tool for both internal and ex-

ternal step threading operations by said tool bar,said cutting edge of said cutting tool beingmounted substantially above a horizontal planepassing through the axis of rotation of the work5 parallel to the direction of reciprocation of saidcutting tool, so as to provide maximum clear-ance for said cutting edge of said , tool when saidwork is being rotated at relatively high speed.

7. In a step threading attachment for lathe,10 a tool feeding carriage movable relative to thework spindle of said lathe, a reciprocating slidemounted on said carriage, means for actuatingsaid slide in step threading movement compris-ing a gear, said gear having a cam on its face,15 a projection on said cam arranged to engage saidreciprocating slide for moving it to and from thework to be step threaded, and a plane surface onthe opposite face of said gear, said gear beingjournaled on a shaft for axial movement along

20 said shaft, and means for axially moving saidgear and its cam axially of said shaft in accurateadjustment so as to effect relative positioning ofsaid reciprocating slide with respect to a workpiece in said lathe, and means for driving said25 gear in accurate synchronous rotation with thework spindle of said lathe.8. In a step threading mechanism, a rotatablework spindle, a tool carrier, a cutting tool mount-

ed on said tool carrier with its cutting edge30 positioned well above the horizontal plane passingthrough the axis of said work spindle, and meansfor actuating said tool carrier during the cutting

operation to reciprocate said cutting edge ofsaid tool, in a plane substantially parallel to said05 first mentioned plane, perpendicular to the axisof rotation of the work spindle.9. In a step threading mechanism, a rotatablework spindle, a tool carrier, a cutting tool mount-ed on said tool carrier with its cutting edge lo-

40 cated well above the horizontal plane passingthrough the axis of rotation of said work spindle,and means for actuating said tool carrier duringthe cutting operation to effect reciprocatingmovement therein in a non-radial direction in a45 plane perpendicular to the axis of rotation ofsaid work spindle. WILLIAM F. GROENE.ROSS M. BACON.

us2311591 - lathe step threading attachment, 1941

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