US2311263A

US2311263A - Dressing device for grinding wheels

Info

Publication number: US2311263A
Application number: US361608A
Authority: US
Inventors: Stewart Gilbert
Original assignee: Ex-Cell-O Corp
Current assignee: Ex-Cell-O Corp
Priority date: 1940-10-17
Filing date: 1940-10-17
Publication date: 1943-02-16
Anticipated expiration: 1960-02-16

Description

4 Sheets -Sheet- 1 Filed 001;. 17, 1940 4 u H E r pa r Ms e w G Feb. 16, 1943. e. STEWART DRESSING DEVICE FOR GRINDING WHEELS Filed Oct. 17, 1940 4 Sheets-Sheet 2 c T N a v N Feb. 16, 1943,.

Filed Oct. 17, 1940 G. STEWART DRESSING DEVICE FOR GRINDING WHEELS 4 Sheets-Sheet 3 ENVEINTO G/7 erf cszfewarfi :1 4,

Feb. 16, 1943. G. STEWART 2,311,263

DRESSING DEVICE FOR GRINDING WHEELS Filed Oct. 17, 1940 4 Sheets-Sheet 4 I J09 49 108 2 10s J11 26 IIT /6 h 45 46 49 14 M8 55 55 J M/J? H I GV/er'fcSfewa r'f CATTOQQYG Fig. 3.

Patented Feb. 16, 1943 tion of Michigan Gilbert Stewart, Detroit, Mich, assiglmr to ex Cell-'0 Corporation, Detroit, Mich., a corpora- Application October 11, 1940, Serial No. 361,608 v 14 Claims.

The invention relates to dressing devices for grinding wheels and the general aim of the invention is to provide a device of this character having improved efficiency and accuracy in operation.

An object of the invention is to provide a dressing device embodying new and improved means for adjusting the device according to the requirements eithe wheel to be dressed.

Another object is to provide a new and improved means ior supporting a plurality pi dressing tools for movement relative to each other and to the grinding wheel.

Another object is to provide novel means for efiecting the movements of the wheel dressins means relative to the grinding wheel through a cycle in which the dressing means is advanced toward the wheel, is moved to dress the wheel, is retracted or withdrawn from the wheel and is returned to an initial or starting position.

Other objects and advantages will become apparent in the following description and from the accompanying drawings in which:

Fig. 1 is a perspective view of a. dressing device embodying the features of the invention.

Fig. 2 is a front view of the device as seen irom the position ofthe grinding wheel.

Fig. 3 is a plan view of the device; omitting the supporting structure for the cradle.

, Fig. 4 is a longitudinal sectional view on a vertical plane taken substantially along the line 4-4 of Fig. 3.

application of Max A. Mathys Serial No. 350,348

filed August 3, 1940. The machine disclosed in said application is adapted for thread grinding operations and in the present application the dressing device has been illustrated and will be described as being arranged to dress a grinding wheel to a thread grinding peripheral contour.

The exemplary device, as may be seen from Fig, 1, embodies an arrangement of several superimposed supporting means and slides including a dresser slide I! for supporting the entire dressing device in operative relation to the grinding wheel li, a dresser base I! which is ad-' iustable to obtain the required setting of the device for different forms 0! threads, a :cradle member or support ii for adjusting the dressing device to the helix angle of the grinding wheel, an approach slide i4 arranged for reciprocatory movement to carry the dressing tools into and away from an operative relation to the grinding wheel, and an actuating slide II movable to traverse the dressing tools carried by the approach slide across the grinding wheel surface to be dressed.

Referring more specifically to the structural relationships, the dresserslide is supported in any suitable manner for set-up adjustments as by a grinding wheel slide it forming a part of the machine structure of the Mathys application as above identified. -As shown in Fig. 4, the plane Fig. 5 is a transverse sectional view on a vertical plane taken along the line 5-4 of Fig. 4.

Fig. 8 is a sectional view on a vertical plane showing details of a dressing tool supporting means and is taken along the line 6-8 of Figs. 7 and 8 are diagrammatic views illustrating various relationships of the dressing tools and the grinding wheel.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail, the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Dressing devices embodying the features of the invention are adapted for association with various types of grinding machines such for exam: ple as that shown and described in the copending upper surface of the dresser slide iii supports a plate I! constituting the dresser base i2. Preferably, the dresser base I! is mounted on the dresser slide I! for relative pivotal adjustment as to enable the dressed mechanism to be properly set to dress a grinding wheel which may be arranged to make cylindrical or tapered cuts. Thus, the dresser slide carries a pivot pin it engaged by the dresser base l2 and such means as spaced clamping plates l9 secured by bolts 20 maintain the desired angular relationship of a dresser base to a dresser slide. The pivot is is located at the forward end of the dresser slide and the vertical axis thereof extends through .a point about which certain of the dresser tools are adjustable. This point will be hereinafter moreparticularly referred to.

At the front and rear ends of the dresser base are upstanding flanges 2| and 22. respectively. having upwardly facing concave ways 23 therein tosupport the cradle member l3. This member is a frame having arcuate front and rear guides 24, 25 complemental to the ways 28 connected by side and intermediate cross bars 28, 21 (Fig. 5). The rear guide 2!. and its 'associated way 23, preferably have an undercut interfitting relation, indicated at 2|, defining the rearward position of the cradle. Th position of angular adjustment of the cradle to the dresser b'ase may be suitably fixed by such means as clamping members 29, "I secured as by bolts ii to the front of the dresser base 12 for bind ing engagement with the front face of the front guide 24. By this adjustment the operator sets the dressing device according to the helix angle of the grinding wheel and the angularity of the adjustment may be suitably indicated by a scale 32 on the front face of guide 24, the edge 33 of the clamp}! being used as an indicator.

The intermediate cross bar 21 is, as may be seen in Fig. 5, of substantial width and has a wide longitudinally extending recess 34 therein. At each side of the recess a rail 35 is secured as by screws 3! and the inner face of each rail hasalongitudinaily extending groove 31.

. slide prevents relative movement of these parts The approach slide H is mounted above the intermediate cross bar 21 and includes, for convenience of manufacture and assembly, lower and

upper sections

38, 39, respectively secured together as by screws 40. The lower section 38 extends between the rails 35 and the side faces thereof have longitudinally extending grooves 4| opposing the grooves 31 in the rails. Interposed between each pair of grooves 31, H, which constitute raceways. is a series ofanti-friction roller elements 42 held in place by a spacer or retainer plate C3 to complete the bearing relationship.

One of the rails, for example; the left hand rail 35, may be laterally adjusted, as by set screws 44, to determine the desired operating relation of the rails, approach slide and hearings in which the frictional resistance to movement of the approach slide relative to the cross bar 21 is at an approximate minimum.

At its rear end the upper section 39 of the approach slide has an upstanding part 45 (Figs.

4 and 5) provided on its upper surface with longitudinally extending undercut or dovetail ways 48 to receive the actuating slide ll. One

surface on the actuating slide that engages one of the undercut ways 46 is defined by a bar 41 in the nature of a gib which is resiliently urged toward the associated ways 46 by such means as springs I! backed by tension adjusting screws ll. The purpose of this arrangement is to enable the frictional resistance to movement of the actuating slide it relative to the approach slide to be adjusted to a point where it is greater than the frictional resistance between the approach slide and the intermediate cross bar 21.

as long as the approach slide is free to move. The permissible movement of the approach slide is relatively short and may be limited in any suitable manner as by pin 60 on the intermediate cross bar engaging a somewhat elongated aperture ii in the lower section 38 of the approach slide.

As soon as the approach slide is moved in either direction to a limit of its movement. continued rotation of the feed screw 55 will move the actuating slide relative to' the approach slide. Hence, considering that the slides are in their retracted or rearward positions, initial rotation of the feed screw 55 will first move the approach slide to its forward limit as shown in Fig. 4, and thereafter continue the forward movement of the actuating slide. Reverse rotation of the feed screw will first move the appreach and actuating slides rearwardly to the limit of movement of the approach slide, and

. finally to return the dressing tools to their initial position.

In the present embodiment, threedressing tools and individually adjustable supporting assemblies therefor are provided comprising, as

may be seen in Fig. 3, two opposed assemblies 2, 63 for dressing the opposite side faces 84, B5 of a peripheral portion of the grinding wheel II and an intermediate assembly 86 for dressing the peripheral face or edge 61 of the wheel.- Each dressing tool assembly includes means for pivotally supporting the toolfor swinging movement relative to the surface of the wheel to be At the rear end of the approach slide is an upstanding bracket ll supportingfa housing ii for the driving mechanism. This mechanism includes a shaft 52 rotatably mounted in the housing ii to extend into a longitudinal bore 53 located centrally of the actuated slide. Rigidly seated in the front end of the bore 53 is a tubular nut 54 engaged by a feed screw 55 on, the end of the shaft 52. Within the housing ii the shaft I52 has a worm wheel 5' secured thereto and engaged by a worm 51 on a drive shaft 58 suitably journaled in the housing. In the present instance power is delivered to the drive shaft II from a motor (not shown) through a flexible drive cable indicated at II in Figs. 1 and 2. A reversible motor is employed for driving the actuating slide in opposite directions.

-Through the relationship of the frictional redressed by that tool.

Referring first to the structure of the intermediate dressing tool assembly 88. a base block 08. Figs. '3 and 4, is mounted on the upper section 39 of the approach slide for pivotal move- 'ment about a pin 89 carried by the approach by opposed set screws 6911 on the block for engagement with a pin 10 carried by the approach slide and extending into a transversely extending slot 11 on the block. Clamping screws 12 or the like rigidly secure the block to the approach slide in any position of adjustment. The block has a longitudinally extending bore 13 supporting a pivot member 14 in a position fixed by a set screw 15.

A supporting member 16 for the dressing tool is in the nature of a swinging bracket having a bifurcated lower end portion providing spaced arms 11 dimensioned to straddle the opposite ends of the pivot member 14. Pivot bearings 18 are seated in opposed recesses provided in the sistances to'movement of the approach and ac- 76 end faces of the pivot member 14, in one of the arms 11 and in a plug 1| carried by the other arm. Spacers ID, or the like, may be interposed between the pivot. member I4 and the arms 11 to protect the pivot bearings. In the present instance, these hearings consist of anti-friction balls. The supporting member near its front .end has an upstanding part 8| which is bored near its upper end, as at 82, to receive the supporting sleeve It in which the dressing tool 84 or diamondholder, is mounted. The axial position of adjustment of the sleeve ll (and consequently of the diamond) may be suitably determined by a micrometer device 8!, the diamond holder being fixed by such means as a back-up screw 86 and a set screw 81.

Toward its rear side, the supporting member 18 carries a rounded head It for engagement with a slot ll formed in a driving cam II. The slot, as shown in Fig. 3, is at an angle to the pivotal axis about which the supporting member It swings, so that longitudinal movement of the cam will swing the supporting member transversely. The driving cam extends over and is secured to the upper surface of the actuating slide it by such means as a clamping screw 8i extending through a longitudinally elongated slot 82 to engage the actuating slide. This arrang'ement enables adjustment of the drivin cam relative to the head ll engaged thereby, to determine the initial position of the intermediate dressing tool.

The oppositely disposed dressing tool assemblies i2, it are substantially alike and it will, therefore, be necessary to describe the structure oi but one assembly. Thus, referring'to Figs. 2, 8 and 6, the dressing tool assembly 83 includes a supporting base 03 which may be formed as an integral upwardly projecting part of the upper section 3! of the approach slide. upper surface of the base is arcuately traversed by a r-slot N and the slots on both bases are formed on radii of equal lengths about a common center point A located within and in close proximity to the perimeter of the grinding wheel and substantially on the center plane thereof. Each slot N is, as shown in 6. engaged by spaced keys 95 secured to, the opposite sides of a block 86; Clamping means 91 on the block 86 positions and accurately maintain the proper relation between the block it and the base 93.

,The block SI carries a pivot member 98 dis posed on an axis which intersects the vertical line through the point A and the construction of the pivot member 9! and its association with a swinging dressing tool supporting member 99 need not be more particularly described since it is Thewheel. A set screw I04 engages the pin ill, and permits pivotal adjustment of the a tool head ll! so as to change the position and the angular contact of the diamond relative to the grinding wheel.

On the upper surface of the support 99 is a rounded head I08 forming part of a ball and socket joint I01 (Fig. 3) by which the swinging support 89 is connected with an actuating rod I08. The pull rod extends rearwardly to a position above the actuating slide II and at its rear end has a ball and socket connection I09 with a slidenut member I I0 adjustable along the length of a longitudinally extending T-slot HI.

The opposed dressing tools N3 of the assem-

q blies

62, 63, may be conveniently adjusted along their associated arcuate grooves 94 to determine the plane of movement of the dressing tools I08 relative to the grinding wheel, these planes being determined by the angles to which the surfaces 64, on the-grinding wheel are to be dressed. The positions of adjustment may be designated by scales H2 or the like on the bases 98 and cooperating indicators Ill on the blocks 96. By adjusting the connections between the actuating rods I08 and the actuating slide IS a proper driving connection between the actuating slide and both

dresser tool assemblies

62, 63 may be readily obtained in all positions of adjustment of these assemblies.

As may be seen in Fig. 2, the three dresser tools are so arranged that one tool will not interfere with either of the other tools in the swinging movement thereof. Thus, the tools are arranged at different vertical levels, the intermediate tool in this instance being at the higher level and the tool head I02 on the right hand assembly 62 being somewhat longer in a vertical direction than the corresponding head on the "assembly 83. The assembly 62 is therefore dis.-

posed above the tool on the assembly 83 and below the tool on the intermediate assembly. It

should be mentioned that the pivotal axis about u I h which the dressing tool on the intermediate assembly, swings, will normally also intersect a vertical line through the point A and that the axis of the pivot pin' i8 about which the dresser base is adjustable with respect to the dresser slide also coincides with this line.

In setting up the machine for operation, the dresser base will be adjusted with respect to the dresser slide according to the form of the thread which is to be ground by the grinding wheel.

substantially the same as that of the 'intermethe supporting member 88 nearest the wheel a vertical bore IN is formed to receive a depending pin III on a tool head ill! in which a dressing tool I" is mounted. A clamping screw IM', or the like, acts with a backing screw! to maintain the dressing tool I03 in position for proper operative engagement with the wheel. The diamond tools are arranged at an angle toward, the periphery of the grinding wheel. Therefore, by rotating the diamond tool I03, after it has become worn, and looking it in a new position by means of the screw IN, a sharp edge or corner may again be presented to the The cradle is positioning according to the helix angle to which the grinding wheel is set. For example, in Fig. 2 the cradle is adjusted to position the tools for dressing a wheel set at a helix angleof 5, Each of the dressing tool assemblies.1s individually adjusted so that each tool will describe a desired path across a surface of the grinding wheel and the several driving connections of the assemblies with the actuating slide are adjusted to locate the initial or starting position of each tool. Thus, the dressing tool on the intermediate assembly 68 is adjusted to a position in which the. diamond will be located initially at one side of the end face 61 (see Fig. 3) for swinging movement on a plane parallel to the desired plane of that face. The opposed assemblies 62. 83 are adjusted along the slots 94 to positions in which the pivotal axis of each assembly is perpendicular to the desired'plane of the associated side face 64 or 65. The actuating rods I08 are adjusted with respect to the actuating slide so that the assemblies .82, 63

will movefrom an-initial position radially outwardly of the end face 61 of the grinding wheel inwardly across the side faces El, 8!. The initial adjustments of the dressing tools are determined with respect to the advanced or forward limit of the approach slide so that in operation the diamonds will be movedby the forward travel of the approach slide into the planes to which the wheel surfaces are to be dressed.

In performing the dressing operation a circuit to the motor which drives the feed screw," is established to turn the feed screw in a direction that will move the actuating slide' forwardly. Because of thegreater friction between the actuating slide and the approach slide than between theapproach slide and the dresser base, the approach and actuating slides will move as a unit untilthe actuating slide reaches its forward limit of travel. At this point, as shown in Fig. 3, the several diamonds are each disposed on the plane tofwhich the grinding wheel surfaces are to be dressed. Continued movement oi the actuating slide (which' movement is relative to the approach slide) will swing each of the dresser .

assemblies

62, 63, 66 in a direction that will carry the diamonds across the corresponding surfaces of thegrinding wheel to dress the wheel. This movement of the diamonds relative to the wheel is illustrated in Fig: '7. It may be noted that the extent of swinging movement of each of the approach slide reaches its rear limit of movement,

the continued travel of the actuating slide will return the tools to their initial positions. It will be evident, therefore, that by the present contion a single driving means having individually adjustable connections with each of the dressing tools, moves the tools through all of their movements relative to the grinding wheel.

The reversal'of the motor for driving the feed screw may be automatic. Thus, as shown in Fig. 3,.a switch, not shown but located in the housing III on the actuating slide, has a contact controlling operator I} I extending therefrom. In the path of travel of the operator I I! and on the opposite sides thereof, are pins H6 and H1 adjustably carried by a bracket H8; The circuit ing, in combination,

, and away from the grinding s,s1 was also serves as the means for effecting the approach and retracting movements of the dressing'tools relative to the grinding wheel. The dressing mechanism may be readily adjusted to dress grinding wheels set for different helix angles or forms of threads.

I claim as my invention:

1. A dressing device for grinding wheels hava support, a base mounted on said support for adjustment about a vertical axis, an arcuate cradle carried by said base for adjustment according to the helix angle of the grinding wheel to be dressed, a first slide carried by said cradle for reciprocatory movement toward wheel, a plurality of dressing tools, means individually supporting each of said dressing tools for adjustment on said slide relative to each other and to the grinding wheel and including pivot means permitting swinging movement of said dressing tools across a surface to be dressed, a second reciprocatory slide mounted on said first slide, individual driving connections between said second slide. and each of the dressing tool supporting means, means for driving said second slide through a reciprocatory stroke, means for imposing a greater frictional resistance to movement between said first and second slides than between said first slide and said cradle, and means for limiting the extent of movement of said first slide.

2. A dressing device for grinding wheels having, in combination, a base, a frame carried by said base for adjustment to the helix angle of the grinding wheel to'be dressed, a first slide carried by said frame for reciprocatory movement toward and away from the grinding wheel,

a plurality of dressing tools, means individually supporting each of said dressing tools for adjustment on said slide relative to each other and to the grinding wheel and including pivot means permitting swinging movement of said dressing tools across a surface to be dressed, a second slide mounted on said first slide, individual driving connections between said second slide and each of thedressing tool supporting means, means for advancing and retracting said second slide, means for imposing a greater frictional resistance to movement between said-first and second slides than between said first slide and said frame, and means for limiting the extent of movement of said first slide.

arrangement is such that when the grinding wheel is to be dressed, a circuit to the driving motor is closed either automatically or by the operator of the machine. The circuit thus established drives. the motor in a direction to move the actuating slide forwardly, which movement continues until the operator 5 strikes pin III to establish a reverse circuit and break a hold ing circuit which has maintained the circuit first established. The return or retracting movement of the actuating slide continues until the operator Ill strikes pin II! to break the last established or reversing circuit.

It will be evident from the foregoing that a 3. A dressing device for grinding wheels having. in combination, a support, a frame carried by said support for adjustment to the helix angle of the grinding wheel to be dressed, a first slide carried by said frame for reciprocatory movement toward and away from the grinding wheel, a plurality of dressing tools, means supporting each of said dressing tools for swinging movement across a surface to be dressed, means for adjusting an opposed pair of said supporting means about a common center, a second slide novel dressing device has been provided in which each of the dressing tools is individually adjustable to dress a grinding wheel to a required cone is are actuated in ing, in combination, a support, a reciproc mounted on said first slide, individual driving connections between said second slide and each of the dressing tool supporting means, means for driving said second slide through a reciprocatory stroke, means for limiting the extent of movement of said first slide, and means for effectini movement of said first slide to a limit prior t1 independent movement of said second slide relative thereto.

4, A dressing device for grinding wheels l'iaii individually supported on said slide for relative swinging movement on different planes, means for adjusting said dressing tools for swinging movement in different angular planes, a second slide mounted on the first mentioned slide, individual driving connections between said second slide and each of the dressing tools for swinging said dressing tools, and driving means for reciprocating said first slide and for moving said second slide to swing said dressing tools.

5. A dressing device for grinding wheels having, in combination, a support, a slide on said support movable toward and away from the grinding wheel, a plurality of dressing tools supported for swinging movement across surfaces to be dressed, means for adjusting said tools to difmeans for supporting each of said dressing tools for swinging movement on a plane parallel to the plane of a surface to be dressed. means for ferent angular planes of movement, a second slide, driving connections between said second slide and each of the dressing tools adjustable in accordance with the difierent positions of said tools, and means for moving said slides.

6. A dressing device for grinding wheels having, in combination, a support, a slide on said support movabletoward and away from the grinding wheel, a plurality of dressing tools supported for swinging movement across a surface to be dressed, a second slide mounted on said first mentioned slide, driving connections between said second slide and said dressing tools, means for driving said second slide movable in the same direction as saidfirst slide, means for limiting the extent of movement of said first slide, and means for imposing a greater frictional resistance to movement between said first and second slides than between said first slide and said support.

'7. In a dressing device for a grinding wheel, the combination of a support arranged to be located adjacent the grinding wheel to be dressed, a pair of spaced members mounted onsald support and disposed one on either side of the grinding wheel, means for adjusting each of said members along an arcuate path about a common center, dressing tools mounted on said members for pivotal movement relative thereto about axes substantially perpendicular to the planes of the surfaces to be dressed by said tools on the grinding wheel, and

common driving means individually and adjustably connected with 'each of said dressing tools. 8. In a dressing device for a grinding wheel, the

combination of a support, a pair of spaced members mounted on said support and disposed one on either side of the grinding wheel, means for adjusting each of said members along an arcuate path about a common center, a dressing tool supported on each member for pivotal movement to traverse the tool across a corresponding surface 7 of the grinding wheel, a third dressing tool pivotally mounted on said-support intermediate said first mentioned dressing tools for swinging movement on an axis paralleling the plane of the grinding wheel, and common driving means individually and adjustably connected. with said dressing tools.

9. In a dressing device for a grinding wheel, v

the combination of a support arranged to be located adjacent the grinding wheel to be dressed, a pair of spaced members mounted on said support and disposed one on either side of the grinding wheel, means for adjusting each of said members along an arcuate path about a common center, a dressing tool supported on each member for pivotal movement relative thereto, a third dressing tool mounted between said dressing tools on said members for movement transversely of the plane of the grinding wheel, said dressing tools individually changing the plane of movement of each tool, a base on which the supporting means is mounted for movement toward and away from the grinding wheel to carry the tools into and out of positions in which their planes of movement coincide with the planes to which the surfaces on the grinding wheel are to be dressed, and driving means for effecting such movement of the supporting means and for swinging said tools through dressing and return strokes.

ll. In a dressing device for a grinding wheel the combination of a plurality of dressing tools, means for supporting each of said dressing tools for swinging movement on a plane parallel to the plane of a surface to be dressed, means for individually changing the plane of movement of each tool, a base on which the supporting means is mounted for movement toward and away from the grinding wheel to carry the tools into and out of positions in which their planes of movement coincide with the planes to which the surfaces on the grinding wheel are to be dressed.

from the grindingwheel to carry the tools into and out of positions in which their planes of movement coincide with the planes to which the surfaces on the grinding wheel are to be dressed, and a single driving means for consecutively moving the supporting means toward the grind ing wheel, moving said tools across the surfaces to be dressed, retracting the supporting means and returning the tools to the starting position thereof.

13. A dressing device for grinding wheels having, in combination, a support, a pair of super-.

imposed slides mounted on said support for reciprocatory movement relative to said support and to each other toward and away from the grinding wheel, a plurality of dressing tools supported on one of said slides for swinging movement across a grinding wheel surface to be dressed, individual driving connections between the other of said slides and each of said dressing tools for effecting swinging movement thereof, and a single driving means for moving said slides together to shift said dressing tools into operative relation to the grinding wheel and for thereafter independently continuing the movement of the slide that is drivingly connected with the dressing tools.

14. A dressing device for grinding wheels having, in combination, a support, a pair of superimposed slides mounted on said support for reciprocatory movement relative to said support and -to each other toward and away from the grinding wheel, a plurality oi dressing tools supported on one of said slides for swinging movement across a grinding wheel surface to be dressed, individual driving connections between 5 the other of said slides and each of said dressin; tools for eiiecting the, swinsing movement thereof, and a, single driving means for shifting said slides as a unit toward and away from a position in which said dressing tools are disposed for operative engagement with the grinding wheel and for thereafter independently continuing the movement of the slide that is drivinsly connected with said dressing tools to swing said dressing tools through dressing and return strokes, and means for so correlating the movements of the slides that their movement as a unit toward or away from the grinding wheel precedes the independent movement of the slide that is drivinzly connected with the dressing GILBERT STEWART.

10 tools.