US2082736A - Truing apparatus for lapping machines - Google Patents

Description

June 1 1937. H. s. INDGE TRUING' APPARATUS FOR LAPPING MACHINES 3 Sheets- Sheet 1 Filed Sept. 28, 1955 HERBERT 5'. INDG'E W ITNESS JMW Wm. wm

June 1, 1937.

H. S. INDGE TRUING APPARATUS FOR LAPPING MACHINES Filed Sept. 28, 1935 3 Sheets-Sheet 3 Qrwam'tcw HERBERT 5.1m) GE W TNESS Patented June 1, 1937 Herbert S. Indge, Westboro, Mass, assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Appiication September 28, 1935, Serial No. 42,583

7 Claims.

This invention relates to lapping or grinding machines, and more particularly to a lap or grinding wheel truing mechanism.

One of the objects of this invention is to provide a simple, thoroughly practicable truing apparatus for truing the flat operative face of a lap or abrasive wheel. Another object is to provide a truing apparatus for truing the opposed operative flat faces of two opposed lapping or grinding wheels. Another object is to provide a truing apparatus which is capable of truing the two opposed operative faces of a pair of opposed lapping or grinding elements simultaneously.

A further object is to provide a pivotally mounted truing tool carrier for swinging the truing tool or tools through an arcuate path across the operative face or faces of a lap or grinding wheel. Another object of this invention is to provide a pivotally mounted truing tool holder which is rocked through an arcuate path across the face of the grinding wheel by a hydraulically actuated mechanism.

A further object is to provide a hydraulically 5 actuated mechanism for controlling the movement of a truing tool across the face of a lap or grinding wheel, in which the truing speed may be readily controlled. A further object is to provide a hydraulically actuated mechanism for moving a truing tool through an arcuate path across the operative face of a lap, in which both the intake and exhaust of fluid are throttled to definitely control the rate of movement of the truing tool. Other objects will be in part obvi- 35 ous or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown one of various possible embodiments of the mechanical features of this invention,

5 Fig. l is a side elevation of a lapping machine and truing apparatus embodying this invention, having parts broken away to more clearly show the construction;

Fig. 2 is a fragmentary cross-sectional view,

50 on an enlarged scale, taken approximately on the line 2-2 of Fig. 1;

Fig. 3 is a combination cross-sectional view and elevation of the mount for the truing apparatus taken approximately on the line 33 of Fig. 2;

Fig. ,4 is a fragmentary elevation, on an enlarged scale, of the pivotal support for the truing apparatus;

Fig. 5 is a cross-sectional View, on an enlarged scale, taken approximately on the line 5-5 of Fig. 1;

Fig. 6 is a fragmentary cross-sectional view, on an enlarged scale, taken approximately on the line i6 of Fig. l, of the binder mechanism for locking the upper lapping element in any desired position;

Fig. 7 is a cross-sectional View through the control valve, on an enlarged scale, taken approximately on the line l-'! of Fig. 2;

Fig. 8 is a cross-sectional view, on an enlarged scale, taken approximately on the line 8-8 of Fig. 2;

Fig. 9 is a vertical section showing a modified form of mounting for the truing tools;

Fig. 10 is a cross-sectional view, taken approximately on the line lfl-H) of Fig. 9, showing the clamping mechanism for the truing tools; and

Fig. 11 is a fragmentary cross-sectional view taken approximately on the line H-l I of Fig. 9, showing the adjusting mechanism for the truing tools.

In the embodiment of the invention selected for illustration, a lapping machine has been shown comprising a base II adapted to support a lower lap l2 and an upper lap I3. The upper and lower laps are arranged for a relative rotary motion to produce a predetermined lapping operation. In the preferred construction, both the upper and the lower laps are rotated preferably in different directions.

Power may be supplied to the machine in any convenient manner, such as by means of a belt arranged to rotate a pulley l5 keyed to a shaft 16 journaled in bearings ll, l8, l9, and 20 in the base I lof the machine and arranged to rotate both the upper and the lower lap. A worm 2! is fastened to the shaft l6 and meshes with a worm gear 22 keyed to a vertical sleeve 23 which is rotatably supported in a bearing 24 within the base of the machine. The upper end of the sleeve 23 supports a spider 25 which in turn supports the lower lapping wheel E2. The rotary motion applied to pulley i5 is transmitted through shaft l6, worm 2i, worm gear 22, sleeve 23 and spider 25 to rotate the lower lap 52. The details of the mounting for the upper lap have not been shown in detail in the present case, since they are not considered to be a part of the present invention. For further details, reference may be had to my prior Patent No. 1,870,328 dated August 9, 1932.

The lapping elements or wheels I2 and I3, as illustrated, are each formed as an annulus of ceramic bonded abrasive grains made like a grinding wheel, each of which is provided with a substantially fiat abrading or lapping surface for simultaneously engaging and abrading or lapping the opposed faces of a Work piece.

The rotatable upper lap I3 is supported by means of a spider 30 mounted on the lower end of a rotatable spindle 3L The spindle Si is rotatably supported in bearings (not shown) in a vertically movable sleeve 32 which is slidably mounted within a projecting portion 34 of an arm 35. The arm 35 is formed integrally with a Vertically extending column 36 which is fixed to the base II. The lap I3 and spindle 3! may be rotated from any suitable source of power, but as illustrated in the drawings is driven by means of a belt from the shaft I6. A pulley ll] is mounted on the shaft I6 and is connected by means of a belt 4! with a pulley 42 mounted on the upper end of the upper lap spindle M. The belt lI passes over a pair of idler pulleys 43 (only one of which has been illustrated in Fig. l) which are rotatably supported on a transverse shaft M. It will be readily apparent from the foregoing disclosure that rotation of the shaft It by means of driving pulley I5 serve to simultaneously rotate both the upper lap I3 and the lower lap i2.

In order that the laps I2 and I3 may be maintained with proper operative surfaces for producing the desired lapping operation, a suitable truing apparatus is essential to permit a truing of the operative faces of the laps when necessary. In the embodiment of the invention illustrated, a pivotally mounted truing apparatus is provided in which a truing tool is mounted on a rock arm and arranged to be swung through an arcuate path across the operative face or faces of the lap. As illustrated in the drawings, this mechanism comprises a vertically mounted rotatable shaft 50 supported in bearings 5| and 52 on a bracket 53 which is rigidly mounted on the columns 36. An arm 54 is mounted on the shaft 50. The arm 54 is provided with an elongated head 55 which is slotted at 55 and arranged to be clamped in adjusted position on the shaft 53 by means of clamping screws 5'! and 58. The screws 51 and 53 pass through clearance holes in bosses 59 and 66 and are screw threaded into bosses GI and 62 so, that the head 55 may be readily clamped in adjusted position on the ver-v tical shaft 5il. A push screw 65 is screw threaded in a boss 66 and abuts against a boss 5?. This push screw serves to spread or expand the head 55 when it is desired to unclamp the arm 54. An end thrust and locating collar I0 serves to locate the head 55 in the desired position on the shaft 50. The collar It is preferably a split collar and arranged to be clamped in adjusted position on the shaft 59 by means of a clamping screw II. The shaft 5c is rotatably mounted in bearing brackets 5i and 52 which are fixedly mounted on the column 36. A thrust washer or collar '55 which fits on a reduced portion IS on the lower end of the shaft 50 and bears against the upper surface of bearing 52 serves to take up the vertical thrust of the shaft 50 and its associated parts. A similar collar or thrust washer 71 also fits on the reduced portion 76 and is held in adjusted position by a pair of lock nuts I8 and IS. The thrust collars l5 and TI together with the lock nuts 18 and I9 serve as an end thrust bearing to hold the shaft 56 in the desired vertical position.

The outer end of the arm 54 is provided with an enlarged head 80 which is arranged to support a pair of opposed diamonds or truing tools 8! and 82, each of which is separately adjusted relative to the head Sfi. The truing tool 8| is mounted in the end of a spindle 83 which is slidably keyed by means of key 83, in an aperture 85 within head 30. An adjusting screw 86 is screw threaded into a threaded aperture 8'! in the spindie 83 and serves to adjust the position of the spindle 8E and the truing tool 8I relative to the head 89. In order that the screw 86 may be held against endwise movement, it is provided with an enlarged head 89 which fits within a counterbored recess 98 in the head 80 and is held in adjusted position relative thereto by means of a cap or cover plate 9|. The diamond or truing tool 82 is held in a similar spindle 35 which is slidably keyed by means of a key 96 within an aperture 97 within the head 88 and is arranged to be adjusted relative thereto by means of a screw 98 which is screw threaded into a threaded aperture 99 within the spindle 95. The screw 98 is provided with an enlarged head II!!! which fits within a counterbored aperture I Ell in the head 3i] and is held in adjusted position therein by means of a cover plate I02. It is readily apparent from the foregoing disclosure that the diamonds or truing tools BI and 82 may each be adjusted relative to the head by manipulation of screws 86 and 98.

In order that the diamonds or truing tools may be locked in adjusted positions on the head 88, the opposite sides of the head are provided with slots I55 and Iflfi which enable portions of the head to be sprung to bind the spindles 83 and in their adjusted position. A binding screw I Ill passes through a clearance hole in a boss I88 and is screw threaded into a boss I09 t0 clamp the spindle 83 and diamond BI in the desired adjusted position. A binding screw IIIl passes through a clearance hole in boss III and is screw threaded into boss II2 to serve as a clamp for the spindle 95 and the diamond 82 in the desired adjusted position. It will be readily apparent from the foregoing disclosure that the diamonds BI and 82 may be readily and precisely adjusted relative to the head lit by manipulation of the clamping screws Iil'l and H6 and. the adjusting screws 36 and 98.

To attain one of the objects of this invention, it is desirable to provide a suitable power operated mechanism for moving the truing tools across the face of the laps l2 and I3 at a slow uniform rate to true the operative faces thereof to form the desired lapping surfaces. In the preferred construction, a hydraulically actuated mechanism is provided to swing the arm 54 to pass the truing tools 8! and 82 through an arouate path across the operative fiat faces of the lapping wheels. A fluid pressure cylinder I26 is pivotally mounted on a stud IZI which is in turn supported in a bracket i522 projecting from the column 36. A piston I23 is slidably mounted within the cylinder 529 and is connected by means of a piston rod I2 3 with a stud I25. Stud I25 is also connected with one end of a connecting rod I26, the other end of which is pivotally connected to a stud I27. The stud I2? is connected to one end of a rock arm I29, the other end I30 of which is locked to the upper end of the shaft Ell by means of a set screw I3I. It will be readily apparent from the foregoing disclosure that when fluid is admitted to the cylinder I20, causing the piston I23 to move therein, this motion will be transmitted through the connecting rod I24, stud I25, connecting rod I26, to rock the arm I29 which in turn serves to rock the vertical shaft 50 and thereby swing the arm 54 and the truing tools 8| and 82 across the operative faces of the laps I2 and I3.

A fluid pressure system is provided to sup-ply fluid under pressure to operate the piston I23. This system comprises a reservoir II5 within the base of the machine. A pump II6 draws fluid from the reservoir II5 through a pipe I32 and forces fluid under pressure through a pipe I33 to a control valve I34. A pressure relief valve I35 is connected in the pipe line I33 to return excess fluid through an exhaust pipe I36 to the reservoir I I5. The control valve I34 is of a slidable piston type and comprises valve pistons I38, I39, and I40 which are formed integrally with a valve stem I4I. This valve serves as a reversing valve and also a speed control or throttle valve to control the direction and speed of movement of the truing tool or tools across the operative faces of the laps. Fluid under pressure from the pipe I 33 enters a valve chamber I42 formed between the valve pistons I38 and I39 and passes out through a pipe I43 into a cylinder chamber I44 to cause the piston I23 to move toward the right, as viewed in Fig. 2, which serves to rock the arm 54 in a counterclockwise direction. During this movement of the'arm 54, fluid under pressure exhausts from a cylinder chamber I45, a pipe I46, a valve chamber I48 formed between valve pistons I39 and I40 and out through an exhaust pipe I49 and through the pipe I36 into the reservoir H5.

The valve stem MI is provided with an operating knob or handle I50. When it is desired to reverse the direction of movement of the arm 54 so as to cause the truing tools to move in a clockwise direction (Fig. 2), the knob I50 is moved into a position I50a, as shown in broken lines in Fig. 2, which serves to shift the valve pistons I36, I39, and I40 into a reverse position so that fluid under pressure from the pipe I33 will pass through valve chamber I48 between the valve pistons I39 and I40 and through pipe I46 into a cylinder chamber I45 to cause the piston I23 to move toward the left, as viewed in Fig. 2, so as to swing the arm 54 and the truing tools BI and 82 in a clockwise direction through an arcuate path across the operative faces of the laps I2 and I3. During this movement of the piston I23, fluid under pressure exhausts from the cylinder chamber I44 through the pipe I43, the valve chamber I42 between the pistons I38 and I39, and out through a pipe I52 and the pipe I36 to the reservoir II5.

In order that the laps I2 and I3 may be trued to produce the desired lapping surface, it is desirable to provide a speed controlling device for the fluid pressure system so that a slow uniform traverse of the truing tool across the face of the laps may be obtained. This is preferably accomplished by providing a suitable arrangement for throttling the. fluid passing through the control valve I34. In the preferred construction, the valve I34 is provided not only with a longitudinal motion to cause a reversal of the direction of flow of fluid within the system but is also provided with a rotary motion which serves to throttle the flow of fluid through the valve. The valve is so constructed that both the intake and exhaust of fluid are throttled to the same extent to provide a slow uniform movement of the truing tool.

The valve stem MI is provided with a serrated portion I55 which is engaged by a spring pressed plunger I56 so that the valve stem I4I may be readily rotated to the desired position and held in the adjusted position. the fluid passing to and from the control valve, the valve pistons I 38 and I 40 are each provided with throttling grooves I60 (Figs. 2 and 8). There are four openings or holes I59 through the valve sleeve I6I and four grooves I60 which extend longitudinally of the valve piston I40 forming lands I55 therebetween. By rotating the valve stem I4I, the lands I between the grooves I68 may close the valve sleeve openings I59 to a greater or lesser extent to throttle the flow of fluid therethrough. Fig. 8 shows a cross section through the valve taken on the line 8-8 of Fig. 2 through the valve piston I40. The valve piston I38 is similarly provided with grooves and lands so that the fluid entering or exhausting from the valve chamber I42 may also be throttled to the same extent. It will be readily apparent from the foregoing disclosure that by endwise movement of the valve stem I4I, the fluid under pressure within the system may be reversed to move the piston I23 in either direction so as to move the truing tools either in a clockwise or counterclockwise direction across the face of the laps to be trued. By rotating the knob I50 and valve stem I4I, the fluid entering or exhausting from the system may be varied from the maximum to a point where the fluid is entirely out off, that is when the lands I65 (Fig. 8) are turned to entirely block the ports I59 in the valve sleeve I6I. By rotating the valve stem to the desired extent, the speed of movement of the truing tools may be accurately controlled to produce the desired lapping surface.

It may be desirable to arrange the truing tools BI and 82 in axial alignment and diametrically opposed to each other so that both of the laps I2 and I8 may be simultaneously trued. A modified construction has been illustrated in Figs. 9, l0, and 11, in which the truing tools 8| and 82 are arranged diametrically opposite to each other. The arm 54, as shown in Figs. 9, l0, and 11, is provided with an enlarged head ISI having a vertically extending aperture I92 arranged to receive a pair of diamonds or truing tool holders I93 and I94. The truing tool holder I94 is provided with a reduced threaded portion I95 which engages or meshes with a threaded aperture I96 within the diamond holder I93. A pair of binding screws I91 and I98 are arranged to bind the diamond holders I93 and I94 in place on the head. Details of only one of the clamping mechanisms have been illustrated since they are both identical in construction. As shown in Fig. 10,

In order to throttle the clamping screw I9! passes through a clearance hole in a slidably mounted bushing 200 and is screw threaded into a central aperture within the slidably mounted bushing 20I. The bushings 200 and 20I are each provided with a transversely extending fragmentary cylindrical surface 202 and 203 respectively which are shaped to mate with the periphery of the truing tool holder I93 and I94 respectively. It will be readily apparent from the above disclosure that when the screw I9! is tightened, the bushings 200 and 20I are drawn together to clamp the diamond holder I93 in adjusted position.

In order that the truing tools 8| and 82 may be readily and separately adjusted, the inner ends of the truing tool holders I93 and I94 are formed as .a spiral gear 255 and 206 respectively. A pair of spiral gears 251 and 208 mesh with the gears 205 and 205 respectively. Gears 2G1 and 208 are mounted on rotatable shafts 209 and -2I0 respectively and are arranged to be adjusted by knobs ZII and 2I2 respectively. The binding screws I91 and I98 are maintained in a clamped position except during adjustment of the diamonds 8| and 82. If it is desired to adjust the diamond 82, the clamping screw I98 is loosened to unclamp the holder I94 while the clamping screw I81 is in a clamped relationship to hold the diamond holder I93 against rotation. Then the knob M2 is turned to rotate the shaft ZIO, spiral gear 208, spiral gear 295, which serves to rotate the diamond holder I94. This movement rotates the screw I55 within the threaded aperture I96 and due to the fact that the holder I93 is stationary serves to cause an endwise movement of the holder I94 to adjust the diamond 82 as desired.

Similarly, when it is desired to adjust the position of diamond BI, the clamping screw I98 is locked in a clamping position to prevent rotation of the holder I94. The clamping screw I91 is unclamped to permit rotation of the holder I93 and the adjusting knob 2II is rotated to cause a rotation of the spiral gear 201 which serves to rotate spiral gear 265 and thereby cause a rotation of the diamond holder I93. Due to the fact that the threaded projection I95 is held stationary, the threaded aperture I96 is rotated on a fixed threaded portion I95 and causes an endwise motion of the holder I93 to adjust the diamond BI as desired.

The upper lap I3 is arranged to be moved vertically with relation to the lower lap. This may be accomplished either by means of a manually controlled or automatically controlled mechanism. For the sake of simplicity of illustration, a manually operable mechanism has been provided comprising a hand wh eel I10 which is mounted on the outer end of a shaft I1I, the inner end of which carries a gear IBI meshing with a rack bar I 32 on the vertically movable sleeve 32. By manipulating the hand wheel I15, the upper lap may be raised or lowered as desired. This mechanism serves to bring the upper lap into operative relation with the work during the lapping operation and also serves to lower the lap until the operative face of the lapengages the truing tool for a truing operation.

In order that the upper lap may be held against vertical movement in a fixed position during the truing operation, means are provided to lock the sleeve 32 in an adjusted truing position. This mechanism comprises a clamping screw I85 which comprises two slidably mounted bushings I86 and I81 each of which is provided with a partial cylindrical surface I88 and I89 respectively, which engage the periphery of the sleeve 32.. The clamping screw I 85 passes through a clearance hole in the bushing I86 and is screw threaded into an. aperture I53 in the bushing I81. By tightening the screw I85, the bushings I86 and I81 are drawn together to clamp the sleeve 32 in rigid engagement with the projection 34 of'the arm 35 so as to lock the upper lap in a truing position. Truing tool BI may then be oscillated through an arcuate path across the operative face of the lap I3 by oscillating the arm 54 by means of a fluid pressure mechanism.

In the operation of this truing apparatus, the

arm 54 is adjusted vertically on the shaft 50 and clamped in adjusted position by means of the locating collar 10 and the arm is then clamped in position thereon by means of the clamping screws 51 and 58. The lap I2 is then set in rotation and the valve I34 operated by means of the knob I50 serves to pass the truing tool 82 across the operative face of the lower lap. By adjusting the screw 98, the truing tool 82 may be brought into the desired truing relation with the operative face of the lap I2. The truing tool may then be oscillated through an arcuate path across the face of the lap until the lap is trued to the desired extent. By adjusting the position of the truing tool, any amount of material may be trued from the lap as desired.

To true the upper lap I3, the hand wheel I10 is rotated to turn the gear I8I which meshes with the rack bar I82 on vertically movable sleeve 32. By manipulating the hand wheel I10, the upper lap I3 may be lowered until the operative face of the lap engages the truing tool 8|. The sleeve 32 may then be locked in a truing position by means of the clamping screw I85. The truing tool 8I may then be oscillated through an arcuate path across the operative face of the lap I3 by oscillating the arm 54 by means of the fluid pressure mechanism. By turning the adjusting screw 86, the diamond or truing tool 8| may be precisely adjusted relative to the lap I3 to true its operative surface to the desired extent.

In the operation of the modified construction, the truing tool supporting arm 54 is moved so that the diamond 82 is oppositeto the lap I2.

The diamond 82 is then adjusted downwardly to contact with the surface of the lap I2. The upper lap I 3 is then lowered by manipulation of the hand wheel I10 so that the operative surface of the lap I3 is brought into truing engagement with the truing tool 8|. Then, by manipulation of the fluid pressure mechanism, the truing tools may be passed through an arcuate path relative to the laps I2 and I3 to simultaneously true the opposed operative surface of the two laps.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment 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 illustrative and not in a limiting sense.

I claim:

1. An abrasive wheel truing apparatus comprising a rotatable abrasive wheel, a movable truing tool support, a truing tool adjustably mounted thereon, means to feed the truing tool relatively toward and from the operative face of said abrasive wheel, means including a fluid pressure piston and cylinder to move said support to pass the truing tool across the operative face of said wheel, and a control valve for regulating both the direction and speed of movement of the truing tool relative to the operative face of said abrasive wheel.

2. A truing apparatus for a lapping machine comprising a rotatable lapping wheel having an operative fiat face, a movable truing tool support, a truing tool adjustably mounted thereon,

means to adjust the truing tool to feed the tool toward and from the operative face of said lapping wheel, means including a fluid pressure piston and cylinder to move said support and traverse the truing tool across the operative face of said lap, and a single control valve therefor, said valve being movable in one direction to control the direction of movement of the truing tool and movable in a second direction to control the speed of movement of the truing tool relative to said lap.

3. A truing apparatus for a lapping machine comprising a rotatable lapping wheel, a pivotally mounted truing tool support, a truing tool adjustably mounted thereon, means to adjust the truing tool relative to the support to permit feeding the truing tool toward and from the operative face of said lapping wheel, means including a fluid pressure piston and cylinder to swing the support so as to traverse the truing tool across the operative face of said lap, a fluid control valve therefor, and a manually operable means to move said valve in one direction to change the direction of movement of the truing tool relative to the lap and to move said valve in a second direction to hold it in a predetermined position to regulate the speed of movement of the truing tool relative to the operative face of the lap.

4. A truing apparatus for a lapping machine comprising a rotatable lapping wheel having an operative flat face, a movable truing tool support, a vertical pivot for said support, a truing tool adjustably mounted thereon, means to adjust the truing tool to feed the truing tool toward and from the operative face of the lapping wheel, means including a fluid pressure piston and cylinder to swing said truing tool across the face of said lap, a single control valve therefor, and means to move said valve longitudinally in one direction to reverse the movement of the truing tool and to rotate and hold said valve in a predetermined position to control the speed. of movement of the truing tool across the operative face of said lap.

5. A truing apparatus for a lapping machine comprising a rotatable lapping wheel, a pivotally mounted truing tool support, a truing tool adjustably mounted thereon, means to adjust the truing tool to feed the tool toward or from the operative face of the lap, means including a fluid pressure piston and cylinder to move said support to traverse said tool across the face of said lap, a control valve therefor, and means to move said valve longitudinally to reverse the direction of movement of the truing tool relative to the lap and to rotate and hold said valve in a desired rotary position to throttle both the intake and exhaust of fluid to and from said cylinder to control the speed of movement of the truing tool relative to the operative face of said lap.

6. A truing apparatus for a lapping machine comprising a pair of opposed flat relatively rotatable lapping wheels, a movably mounted truing tool support, a pair of opposed truing tools adjustably supported thereon, means to independently adjust each of said tools relative to the support, means including a fluid pressure piston and cylinder which are operatively connected to move said support to simultaneously traverse the truing tools across the operative faces of said lapping wheels, and a control valve for regulating both the direction and speed of movement of the truing tools relative to the operative faces of said lapping wheels.

7. A truing apparatus for a lapping machine comprising a pair of opposed flat relatively rotatable lapping wheels, a movably mounted truing tool support, a pair of opposed truing tools adjustably supported thereon, means to independently adjust each of said tools relative to the support, means including a fluid pressure piston and cylinder which are operatively connected to move said support to simultaneously traverse the truing tools across the operative faces of said wheels, and a control valve in said system which serves when moved in one direction to reverse the direction of movement of the truing tool and when rotated serves to throttle the fluid under pressure to control the speed of movement of the truing tools across said lap.

HERBERT S. INDGE.

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