Патент USA US2132941код для вставки
Oct. 11, 1938. c. G. FLYGARE 2,132,941 ROLL GRINDING'MAGHINE Filed Dec. 24, v1955 ’ 4 sheets-sheet 1 [2:13 \ CHRI. L_?.FLYGHRE @Mmmm Oct. 11, 1938. 2,132,941 c. G. FLYGARE ROLL GRINDING MACHINE Filed Dec. 24, 1955 4 sheets-sheet 2 \\ \ \\ \\\ rm. JMW" . n h - CHRI. E'. Fl YGHRE Oét. 11, 11938. c. c5.l FLYGARE 2,132,941 ROLL GRINDING MACHINE' Filed Dec. 24, 1935 4 Sheets-Sheet 3 oct. 1l, 1938. Q_ G, FLYGARE 2,132,941 ROLL GRINDING MACHINE wel“ /67/07 /oo l /0/ L . F/G'. Ä gmc/MM Ünm. G. FLYGHRE mwmâàzm- anw-W 2,132,941 Patented Oct. 11, 1938 lni'rlazls'l?v OFFICE 2,132,941 UNITED STATES nom. Gammo MACHINE Carl G. Fly‘xare. Worcester, Mall., nsignor to Norton Company, Worcester, Mass., a corpora tion o! Massachusetts Application December u, 193s, serial ne. sur: z claim. (ci. 514s) This invention relates to a grinding machine, and more particularly to a crowning attachment for a roll grinding machine to generate a prede termined crown onthe periphery of 'a roll. One of the objects of this invention is to make a simple, thoroughly practical crowning attach ment for a roll grinding machine._ A further ob ject of this invention is to provide _a roll crown ing attachment for a roll grinding machine in 10 which the wheel slide is rocked toward and froml the axis of the roll. A further object is-to provide a roll crowning attachment in which the grind ing wheel is rocked toward andl from the work axis in timed `:relation with the work table re 15 ciprocation to produce the‘desired crown. An other object is to provide such a crowning ' mately on the line 4--4 lof Fig. 3, showing the table traversing mechanism; ` . Fig. 5 is a fragmentary cross sectional view, on an enlarged scale, showing the backlash elim inating mechanism for eliminating the backlash 5 between the table rack .and the cross shaft; Fig. 6 is va fragmentary sectional view, taken approximately on the line 6-8 of Fig. 2, on an enlarged scale, showing the backlash eliminating mechanism between the worm and worm gear for lo driving the crowning cam; Fig. 'I is a vertical sectional view through the driving gear, on an enlarged scale, showing the means for eliminating the backlash in the gear train; ' 15 Fig. 8 is an end elevation of the backlash elim gear shown in Fig. 7; and attachment which canbe readily disconnected to inating Fig. 9 is a fragmentary sectional view, on an permit truing of the" grinding wheel while the v enlarged scale, taken approximately on the line wheel remains stationary. ' 20 20 A further object' of this invention is to provide - 9_9 of Fig. 8. A roll grinding machine has been illustrated a roll forming attachment in which the grinding wheel slide is rocked toward and from the work in the drawings comprising a base III which sup ports a longitudinally reciprocable work table axis during the relative longitudinal reciproca tion therebetween, in which the crowning device II on the usual flat way I2 and V-way I3. The 25 may be readily disconnected to stop the rocking' vlongitudinally reciprocable table II is provided 25 ' of the grinding wheel and may be readily con _ nected so that the rocking motion is picked up in identically the same position prior to stopping the motion for truing. 30 K Another object of this invention is to provide a roll crowning attachment in which the grind ing wheel is rocked toward and from the work axis by a mechanism actuated by the work table reciprocation, in which backlash is entirely elim 35 inated between the driver and the cam for rock ing the wheel slide. Other objects will be in part obvious and in part pointed out hereinafter. This invention accordingly consists in the fea tures of construction, combinations of elements, and arrangements of parts, as will be exemplified 40 in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims. ‘with a rotatable work support comprising a mo tor driven headstock I6 and a footstock I1 which serve to rotatably support a roll I5 to be ground. The roll I5 may be mounted on centers, as is ‘ common practice in the art, or ii the roll is very 3o massive in construction, it may be mounted in journal rests (not shown), as shown in the prior United States patent to Norton No. 1,096,188 dated May 12, 1914, to which reference may be had for the details of the support for the work. 35 A rotatable grinding wheel 2U is supported on a rotatable wheel spindle 2l which is in turn sup ported on a wheel slide 22. The wheel slide 22 is connected by a pair of aligned studs or trun nions 23 arranged on opposite sides of the wheel 40 slide, and which are supported on a transversely movable intermediate slide 24. The intermedi ate slide 24 is arranged to slide transversely on the base I0 on a pair of spaced slideways 25 (only In the accompanying drawings, in _ which is one of which has been shown). The intermedi- 45 .Ca shown one 'of various possible embodiments of the ate slide 24 is arranged to be moved transversely as mechanical features of this invention, Fig. 1 is a front elevation of a grinding ma-v relative to the base Ill by means of a suitable wheel feeding mechanism. This mechanism may chine embodying this invention; _ Fig'. 2 is a cross sectional view through the be of any well-known type, such as, for example, that shown in the prior United States Patent to 50 50 grinding machine, on an enlarged scale, taken ap Norton No. '162,838 dated June 14, 1994. This proximately on the line 2--2 of Fig. 1; Fig. 3 is a fragmentary elevation, on an en larged scale, having parts broken away to show the table traversing mechanism; 55 ' Fig. 4 is a cross sectional view, taken approxi mechanism may comprise a half nut 28 depend ing from the transversely movable intermediate slide 24. 'I'he half nut 2l mates with a rotatable feed screw 29 which is journaled in bearings 55 2 2,182,941 (not shownl inthe base |0. 'I'he front end of the feed screw 29 is provided with a gear 30 which meshes with a gear 3| ymounted on the rear end of a rotatable- shaft 32. 'I’he shaft 32 is rotatably supported in the base I0 and is pro vided on its front end with a gear 33 meshing with a gear 34> mountw on a rotatable shaft 35, the outer end» of which supports a manually oper able hand feed wheel 36. By rotation of the 10 hand wheel 36, a rotary motion may be trans mitted to the gears above deseribed to rotate the usual manner by means of a reversing lever 6||_which is actuated by reverse dogs 6| and 62 which are adjustably supported in a T-slot 63 on the front of the work table Il. The reverse leverV operates through a load and fire-mechanism 64 to control the movement of the clutch 5| to con trol the direction of reciprocatory movement of the table H. A ì The shaft 51 carries a gear 10 which meshes with a gear 1| mounted on a shaft 12. The shaft 10 12 also carries a gear 13 which meshes with a cross feed screw 29 which serves to cause anl gear 14 mounted on the shaft 42. endwise movement of the’ half nut 26 to feed the intermediate slide 2e and the wheel slide 22 In order that the power reciprocation of the 15 either toward or from the work piece I5 to grind . table I | may be disconnected, a clutch member 15 is interposed between the gear 1| and the gear the roll I5 tc- a predetermined size. I In the grinding of cylindrical rolls for a roll ing mill, it is frequently necessary te produce a roll -which is not a true cylinder but which is 20 vprovided with an outer surface which is formed either concave or convex to a deñection curve or 15. When the clutch is in the position illus trated -in Fig.` 4,'the power reciprecation of the table is disconnected. A yoked member 16 en gages the clutch member E5 and is supported by a longitudinally movable shaft 11 which is actu 20 ated by a lever 1e on the front of _the machine base. When the lever is rocked toward the ma the drawings. the form or crown on the roll I5 chine base, the shaft 11 is moved toward the 25 is produced by rocking the wheel slide 22 about left, as viewed inl Fig. 4, to move- the clutch member '15 in the same direction to engage it 25 its pivot 23 and relative to the transversely mov able intermediate slide 24 as the roll I5 and with a clutch member 19 which is formed in grinding wheel 20 are reciprocated longitudinallyl tegral with the gear 13. When the clutch mem ber 15 is moved into engagement with the clutch relative to each other. . member 19, the'power rotation of the gear 1| is 30 In- the construction illustrated in the drawings, transmitted through the gear 13, the gear 14, the 30 the work supporting table Ii is reciprocated lon pinion 4|, to the rack 40 to reciprocate the table gitudinally relative to the base I0 and the grind ing wheel 20 to traverse the roll being ground || longitudinally relative to the base I0. For past the operative face of the grinding wheel 20. further details of disclosure as to the manual’or 35 The table is provided'with a depending rack power traverse of the table I I, reference may be bar 40 by which the table may be traversed by a had to the disclosure in the above-mentioned 35 otherwise, according to the requirements of the lrolling mill. In the machine, as illustrated in manual or power traverse mechanism, .such as ' that shown in the prior United States patent to Norton No. 762,838 dated June 14, 1904. This 40 mechanism has not been shown in detail, since it is not considered part of the present invention; and reference may be had to the above-men tioned patent for details of disclosure. 45 50 prior patent to Norton. In order to produce a predetermined rocking motion of thewheel spindle 22 to rock the grind ing wheel- 20 toward and from rthe axis of the roll I5, itis desirable to provide a mechanism to time the rocking motion of the wheel with the 40 longitudinal relative reciprocation between the A gear ¿I4 meshes with the rack 40 and is wheel 20 and the roll I5. This is preferably ac mounted lon a rotatable shaft 42 which, may be eomplished by providing a gear 90 which meshes `with the table driving rack _40 on the under side rotated manually by means of a gear 43 mounted vof the table ||. The gear 90 is mounted on a on the outer end of the shaft 42. The gear 43 rotatable shaft 9| which is journaled in bearings meshes with a gear'44 rotatably mounted on a stud 45. A manually operable traverse wheel 46 in the base I0 of the machine. The rear end of the shaft 9| is provided with a gear 92 meshing is mounted on a hub of the gear 44 and con nected thereby, by means c-f which the table || with a gear 93 mounted on a rotatable shaft 94. 50 may be traversed iongitudinally 0f the base I0 VThe shaft 94 also carries a gear 95 which meshes through the gear 44, the gear 43, the shaft 42 and with a gear 96 mounted on 4a rotatable shaft. 91. The shaft 94 and the gears 93 and 95 carried the gear 4i meshing with the rack bar 40. The table |I may be reciprocated longitudinally thereby are supported on a swinging arm 98 by a power operated mechanism, as shown in the which is supported to, rotate on the shaft 9|. pri-or patent above referred to. This mechanism This permits the gear 96 to be changed when may comprise a rotatable power driven shaft 50 desired and the gear 95 to be swung into proper mesh with the gear 96 and locked in mesh there which is driven by a multiple speed drive con with by a . clamping screw 99 which passes 60 tained within the casing 5I, details of'which have not been shown in the present case since they through the bracket 98 and is threaded into a 60 are not considered part of the present invention. portion of the base I0. The outer „end of the For details of this mechanism, reference may shaft 91 is preferably formed as a splined shaft be had to the above-mentioned prior patent. 'I'he >|00 which ’ passes _through a correspondingly 65 rotatable shaft 50 drives a clutch member 5| shaped aperture within a worm I0| which vis ro which is arranged to engage either the clutch tatably supported within a gear easing |02. The 65 member 52 or the clutch member 53 which are gear casing |02 is rigidly fixed to the trans ' formed integral with bevel gears 54 and 55 re versely movable slide 2€. The worm I 0| meshes spectively. 'I‘he bevel gears 54 and 55 mesh with with a worm gear |03 mounted on a transverse 70 a large bevel gear 56 mounted on the front end shaft |04 ,iournaled in bearings |01 and |0:_.-‘= of a rotatable shaft 51. 'I'he large bevel gear; 56 within the gear casing |02. The shaft |04 sup= is rotated in either direction, depending'upon the engagement of the clutch member 5| with either the clutch member 52 or 53. 75 The clutch member 5| maybe shifted the ports a rotatable cam | | 0 which is arranged to engage a rotatable follower roller ||| which is keyed to-a stud |I2. The studl |I2 is rotatably supported in bearings I I3 and |ë‘4 which are held _2,182,941 in a casing I|5 which is rigidly fixed to the rock ing wheel slide 22. The gear casing |52 is provided with an up wardly projecting stop surface ||5 which is ar ranged to be engaged by an adjustable screw ||1 which is threaded into a bracket ||5 which is fastened to the rear end of the rocking wheel slide 22. If it is desired to _hold the wheel slide against rocking motion, the screw |_|1 may be 10 adjusted to raise the rear end of the wheel slide 3 thereto. The nut |35 is provided with a cup shaped extension |35 toward the right. as viewed in Fig. 5, which is provided with an internal thread |31 meshing with a threaded portion |35 on the sleeve |21. It will be readily apparent from the foregoing disclosure that when the nut |35 is rotated while the shaft' 5I is held stationary by applying a wrench to an end portion |45 thereof, rotation of the nut |35 serves through the threads |31 and |35 to cause an endwise movement of the 10 sleeve |21 either to clamp or unclamp the sleeve operative engagement with the cam` ||5, so that |2| to the portion |22 of the shaft 5|. In order to eliminate the backlash. a gear | 45 even though the cam ||5 is rotated by the longi tudinal movement of the work table ||, no rock-r is rotatably mounted on the sleeve |2| and is of 16 ing motion will be transmitted to the wheel the same size and having the same number of teeth as the gear 55. 'I'he gear 55 is provided with slide 22. a plurality of projecting lugs |45 which are ar In orderthat the roll being formed may be ac curately ground to a predetermined crown, it is ranged to be engaged by a plurality of lugs |41 -projecting from the gear |45, the contacting faces essential that the grinding wheel 25 and its sup 20 porting slide 22 be rocked through an identical of the lugs |45 and '|41 being at an angle to the axis of rotation thereof and at an angle slightly path when the table || is reciprocated in either direction. Due to the backlash in the gear drive, greater than the angle of repose. The gear |45 this is a diillcult problem since when the table` is urged toward the right, as viewed in Fig. 5. is reciprocated longitudinally in one direction, by a plurality of springs |55 which extend in 25 the backlash in the gear connection between the apertures |5| in the hub of the gear |45 and are table rack and the cam for rocking the wheel interposed between the gear |45 and a collar |52 slide will be taken up and the wheel will be moved adjustably positioned on the sleeve |2|. The col through one path and when the table is reversed lar |52 may be adjusted longitudinally relative in its direction of movement by the shifting of to the sleeve |2| by means of the threaded col~ 30 the reverse lever 55, the change in direction of lars |53 and |54. By adjusting the collar |52 the movement of the rack 45 serves to first take along the sleeve I2 I, the tension of the spring |55 up the backlash in the gear drive between the may be varied so that the springs cause the sur 22 so that the follower roller ||| is raised from 15 20 25 30 rack 45 and the cam ||5 before the rocking move merit of the wheel slide starts in the reverse di 35 rect‘ion, thus providing a variable which serves to cause the grinding wheel to rock in a different path on its stroke in opposite directions. In order to eliminate this difficulty, a series of backlash eliminators have been provided to take up the 40 backlash between the worm |5| and the cam |||| and to eliminate any backlash in the gear train 52, 53, 55, 55, thus eliminating lost motion so that when the table || is moved- in either direction, an identical rocking motion is transmitted to the grinding wheel 25 when the roll I5 and table ||are reciprocated in either direction. En order to eliminate the backlash between the rack 45 and the gear 55, a suitable mechanism is provided. The gear `55 is keyed by a key |25 to a sleeve |2| which is rotatably supported on a reduced portion |22 of the shaft 5|. The sleeve |2| is rotatably journaled in bearings |23 and |24 which are fixed to the base I5 so as to provide a ñxed rotary support for the sleeve |2|. The sleeve |2| is provided with a plurality of slots |25 at its left-hand end, as shown in Fig. 5, and the outer surface of this end of the sleeve is tapered to mate with an internal conical surface |25 within a rotatable sleeve |21 mounted on a fur ther reduced end portion |25 of the shaft 5|. The sleeve |21 is slidably keyed to the shaft |25 by a key |29. The sleeve |21, when moved toward the right as viewed in Fig. 5, contracts the split end of the sleeve | 2| and clamps it securely to the 65 reduced portion |22 of the shaft 5|. To readily adjust the sleeve |21, a nut |35 is rotatably mounted on a reduced portion v|3| of the shaft 5| and is held in place-thereon by means of thrust washer |32. Thrust washer |33 is inter posed between the inner surface of-the nut |35 and the shoulder on the reduced portion |3| of the shaft 5|. A pair of nuts |34 and |35 serve to lock the nut in adjusted position on the por tion |3| of the shaft 5| so that it is free to rotate 75 thereon but has no endwise movement relative face |41 to slide on the surface |45 so that any lost motion between the gear 55 and the rack 45 is taken up by the rotation of the gear |45 due 35 to 'the vangular thrust of the lugs |45 and |41. The collar |52 is provided with a pin | 55 which fits loosely within an aperture or hole |51 in the hub of the gear |45, so that the gear |45 can rotate relative to the collar |52. By varying the tension 40 of the springs |55, the opposed thrust of the two gears 55 and 45 may be varied so as to eliminate any lost motion and to exert the desired pressure of the gears |45 and 55 on the rack 45 so that the shaft 5| is rotated in unison with the rack when the rack moves in either direction to rotate the gear 55. .A similar backlash eliminating device is pro vided between the worm wheel |53 and the cam |l5. As illustrated in Fig. 6, the worm gear |53 50 is formed in two halves. The part |53 is connected by a key |55 to the shaft |54. The half |5| of the worm gear |53 is rotatably mounted on the shaft |54 and is provided with an outwardly pro jecting lug |52 which engages a correspondingly shaped lug |53 which is formed as an integral part of the collar |54 which is slidably keyed to the shaft |54 by a key |55. The collar |54 is urged toward the right, as viewed in Fig. 6, by a plurality of springs |55 which are contained with 60 in apertures |51 in the collar |54 and which bear against an adjustable collar |55. The collar |55 may be adjusted longitudinally on the shaft |54 by the adjusting collars les and |10. A pin nl is ilxed to the collar |55 and slides within .an en larged aperture or hole |12 within the collar |54 so that the collar |54 can rotate relative to the collar |55. By adjusting the position of the col lar |55, the tension of the springs |55 may be adjusted, so that the lugs |52 and |53 cause the gear section |5| to be rotated relative to the worm gear part |53 which is keyed to the shaft so as to eliminate any backlash between the worm wheel |53 and the worm |5|. A further backlash eliminating device is pro 75 4 2,132,941 vided in the gear train 92, 93 to eliminate any backlash or wear betweenA said gears. As illus trated, the gear 92 is formed as a two-part gear. Gear 92 is keyed to the Vshaft 9| by a key |80. A second part of the gear 92 is formed as an annu lar ring |8| having teeth cut therein to mate with the teeth of the gear 9|. The ring gear |8| fits on a hub portion |82 oi' the gear 92 and may be locked thereto by clamping screws Ii83 and 10 |84 which pass through elongated slots |85 and |86 in the gear ring |8| and are screw threaded into the gear 92. In order to eliminate the backlash between the gears 92 and 93, it is necessary to adjust the ring 15 gear | 8| relative to the gear 92. To facilitate ad justment of the gear | 8| relative to the gear 92, ' the gear ring |8| is provided with a pair of dia metrically opposed conical surfaces |81 and |88 which are countersunk into the outer surface of 20 the gear |8|. A pair of- screws |89 and |90 pass through the conical apertures |81 and |88 and are screwthreaded into the gear 92. Each of the screws> |89 and |90 is provided with a conical sur face | 9| which is shaped so that an _element of 25 its surface coincides with an element of the coni cal counterbored surface |81 or |88. To adjust the gear ring |8| relative to the gear 92,> the screws |83 and |84 are loosened and then by slacking -off on the screw |90 and tightening the 30 screw | 89, the ring gear | 8| may be moved in a counterclockwise direction relative to the gear 92 to eliminate the backlash between the gears. When the required adjustment has been made, the ring gear | 8| and the gear 92 are clamped 35 together by tightening the screws |83 and |84. The tumbler gear 95 may be adjusted to mesh to a greater or lesser extent with the gear 96 by swinging the bracket 98 so that the backlash be-tween these two gears may be eliminated. It will> thus be seen that a driving mechanism 40 has been provided which Iserves to rock the grind ing wheel 20 through a predetermined path. when the table | | is reciprocated longitudinally and moves in either direction to produce a predeter mined concave or convex crown upon the roll be ing ground, depending upon the nature of the cam | I0 which ismounted on the machine. It may be desirable during the truing operation to disconnect the crowning attachment so that the wheel 20 may be trued while it remains sta tionary, that is with the rocking movement there of stopped. This is preferably accomplished by unlocking the sleeve I2| from the shaft 9|. It is desirable that the crowning attachment be dis 55 connectedv in such a way that after a wheel tru ing operation, the crowning attachment may be picked up when the table is in a predetermined I position so that the grinding operation on the roll being ground may be continued and the desired 60 crown produced after the truing operation has ~ been completed. In the preferred construction, an index finger 200 is fixed to the table || and is arranged to be aligned with a fixed point 20| pro jecting from the base |0. An indexing finger 202 similarly projects from the base |0 and is ar ranged to serve as an'index for a graduated scale 203 arranged on the periphery of the sleeve |21. To disconnect the crowning attachment for tru ing so that the crowning movement of the wheel may be picked up at the same point after truing, the table || is traversed until the index finger 200 is aligned with the fixed point 20| on the base |0. The reading of the scale 203 opposite the ñnger 202 is then noted and the sleeve |21 then with 75 drawn to disconnect the sleeve I 2| to stop the rocking movement of the grinding wheel during the truing operation. After the grinding wheel 20 has been trued to the required extent, the table is again moved so that the index finger 200 is aligned with the ñxed index point 20| on the base |0 and a wrenchis applied to the projection |40 of the shaft 9| to rotate the shaft 9| and the sleeve |21 until the predetermined graduation on the scale 203 coincides with the index iinger 202 . at which point the sleeve |30 is rotated to move 10 the sleeve |21 toward the right, as viewed in Fig. 5, to clamp sleeve |2| to the shaft 9| and thereby start the crowning> movement of the grinding wheel in identically the same position as prior to the truing operation. The operation of this machine will be readily apparent from the foregoing disclosure. The table dogs 6| and 62 are adjusted to the desired position to permit a reciprocation of the roll 50 to. pass the face to be ground across the periphery 20 of the grinding wheel- 20. The change gear mechanism on the rear of the machine is then ad justed to the proper gear ratio for producing a crown of the predetermined extent.' A roll to be ground is then placed either on centers on the machine or,'as above stated, on journai°rests (not 25 shown). The roll is then rotated and the recip rocation of the table || started and the grinding wheel 20 is fed into grinding relation with the roll |_5 by manipulation of the manually operable feed 30 wheel 36. The grinding operation may then be continued until the roll has been ground to a predetermined crown and finished. It will thus be seen that there has been pro vided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodi ments may be made of the above invention and as many changes might be made in the embodi 40 ment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as il lustrative and not in a limiting sense. I claim: 1. A roll grinding machine comprising a base, a longitudinally movable Work supporting table thereon, a rotatable work support on lsaid table, means including a rack to reciprocate said table longitudinally, a transversely movable slide, a rotatable grinding wheel, a support for said wheel, pivotal connections between said support and slide, a rotatable cam, a shaft supporting said cam which is rotatably mounted on said slide, a follower roller rotatably mounted on the wheel support and arranged to engage said cam, a worm and worm gear supported on said slide and ar ranged to rotate said cam, means to eliminate the backlash between the worm and worm gear, a. ro tatable shaft in the base, gear connections be 60 tween the table rack and said shaft whereby the shaft is rotated when the table is reciprocated, a backlash eliminator associated with said gearing, change gears connecting the other end of said shaft and said worm, and means to eliminate 65 backlash- in said change gears so that the rocking movement of the wheel slide is accurately syn chronized with the table reciprocation so as to produce a predetermined crown' on the roll being ground. 2. A roll grinding machine comprising a base, a longitudinally movable work supporting table thereon, a rotatable work support on said table, means including a rack to reciprocate said table longitudinally, a transversely movable slide, a ro 2,132,941 I 5 tatable grinding wheel, a wheel spindle to sup port and produce a predetermined crown on the port said wheel, a support for said wheel and roll being ground, means to disconnect said driv spindle which is pivotally mounted on said slide, ing connections to stop the rocking motion of a rotatable cam mounted on the end of said slide, the wheel, and means including a. graduated scale a follower roller arranged to engage said cam and supported on said wheel support, driving connec and index to connect said driving connections so that the wheel is rocked in the same predeter tions between the table rack and said cam where by the cam is rotated in synchronism with the mined path after truing of the grinding wheel. , table reciprocatìon so as to rock the wheel sup CARL G. FLYGARE.