US1861279A - Grinding machine - Google Patents

Description

May 31, 1932. MATHEWSQN 1,861,279

GRINDING MACHINE Original Filed July 19. 19 6 Sheets-Sheet l I. MATHEWSON May 31, 1932.

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MJ.MATHEWSON GRINDING MACHINE Original Filed July 19, 1927 6 Sheets-Sheet 5 May 31, 1932. M. MATHEWSON GRINDING MACHINE Original Filed July 19, 1927 6 Sheets-Sheet 6 Patented May 31, 1932 UNITED STATES PATENT oFi-icr.

MAXWELL I. MATHEWSON', OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO BROWN 86 SI-IARPE MANUFACTURING CGMPANY, A CURPORATION OF RHODE ISLAND GRINDING MACHINE Original application filed July 19, 1927, Serial No; 206,917. Divided and this application filed January 3, 1930. Serial No. 418,214.

The invention relates to grinding machines and more particularly to that type of machine in which the grinding wheel is mounted on a carriage to move toward and away from the work and the work is mounted on a work supporting table to move back and forth longitudinally of the grinding wheel spindle.

The objects of the invention are to reorganize ant improve the construction and operation of the several cooperating elements of a grinding machine to secure a smoother and more efficient operation ofthe machine, to extend still further the automatic operation of the several cooperating elements, and finally to secure a more adequate control of these elements by the operator.

With these objects in view, the invention consists in the devices, combinations and arrangement of parts hereinafter described and claimed.

The several features of the invention and the advantages to be obtained thereby will be readily understood by those skilled in the art from the following description taken in connection with the accompanying drawings in which Fig. 1 is a view in front elevation of a grinding machine embodying the present invention; Fig. 2 is a view in right side elevati on illustrating particularly the motor and connections for driving the machine; Fig. is a view in front elevation of a port on of the machine with parts broken away; Fig. is a. View in right elevation partly in section, taken on the line 4--4 of Fig. 3; Fig. is a detail sectional view of the cross feed control mechanism taken on the line 55 of Fig. 8; Fig. 6 is adetail view of the hand adjustment for the power cross feed mechanism; Fig. 7 is a sectional view in right elevation taken on the line 77 of Fig. 6; and Fig. 8 is a sectional View in right elevation of the cross feed control mechanism taken on the line 88 of Fig. 5.

Referring to the drawings, the machine illustrated comprises a frame 12 on the front portion of which is mounted a work supporting table 14 which is adapted for transverse movement on ways 16 and is provided with a headstock l8 and a footstock 20. A rotary grinding wheel is indicated at 22 setween the work support and the Wheel spindle carriage to drain off the water which is contlnuously poured over the work during the grinding operation.

A power drive is provided for the table 14 including change speed and reversing mechanism which is adapted to drive the table at a number of different speeds. Movement is transmitted from some source of power such as the motor indicated in dotted lines at 30 through a belt 32 onto a driving shaft 34, and by means of a belt 36 from the driving shaft 34 to a pulley 38 on a shaft 40 which is connected with the change speed gearing and the reversing mechanism for the table drive and the headstock drive in the gear box 42. A reciprocating movement is transmitted to the work supporting table from the shaft 40 through a reversing mechanism which comprises the gears 44 and 46 (see Fig. 3) loosely mounted on the shaft 48 and driven in opposite directions by the change speed mechanism from the shaft 40. A gear clutch member 50 is loosely mounted on the shaft 48 between the gears 44 and 46 to engage with one or the other of them and meshes with an idler gear 52 mounted on a shaft 53. The gear 52 in turn meshes with agear 54 which is screw thread-ed for a limited travel on the driving shaft 56 for the power feed to pro vide a dwell at the end of the table travel in each direction. Abutting the end of the driving shaft 56 is a clutch shaft 58 which carries a clutch member 60 adapted to engage with the corresponding member 62 formed on the end of the driving shaft 56 and also has keyed to turn therewith a worm gear 64 which is fixed against endwise movement between two arms of a bracket 66 forming a portion of the machine frame. The table is driven from the worm gear 64 through a corresponding gear 68 carried on a shaft 70 which has secured thereto a gear adapted to engage a rack on the table. This construction is more fully described and illustrated in the inventors pending application, Serial No. 206,917, filed July 19, 1927, for grinding machines, of which the present application is a division.

The mechanism for reversing the table is automatically operated at predetermined points in the travel of the table in each direction by adjustable dogs carried on the table which cooperate with a reversing lever mounted on the stationary frame. The dogs indicated at 83, 84 and 86 are mounted in a T-shaped slot 88 on the table and are constructed and arranged so that they may be readily moved along by the operator and at the same time, are self-locking in position. The reversing lever which cooperates with the dogs is indicated at 98 pivotally mounted at 100 on the machine frame. It is connected at its lower end to the sliding bar 102 and the load and fire mechanism which is generally indicated at 104 for actuating the reversing clutch. The load and fire mechanism is actuated from the reverse lever by means of the yoke 106 which is pivotally connected at 108 to the sliding bar 102. F or a detailed description of the load and fire mechanism, reference may be had to the patent to H. E. Townsend, No. 1,120,762, dated February 23, 1915. The upper end of the reversing lever 98 comprises a block 110 which is adapted to come into contact with the dogs 83 and 86 and is slotted to receive a small detent lever 112 which may be positioned to come in contact with or to avoid the dog 84, as desired.

The connections for driving the table either by power from the driving shaft 56 or by hand comprise the clutch shaft 58 and worm gear 64 meshing wtih the gear 68 connected to the cross shaft as above described. The clutch shaft 58 is provided with the clutch members 60 and 132 and is movable in one direction to engage the corresponding clutch member 62 formed on the abutting end of the driving shaft 56 for the power feed and is movable in the opposite direction to engage W113l11 the clutch member 136 for the hand feet.

The hand feed for the work table comprises a hand wheel 138 mounted on a shaft 140 to which is secured the worm 142 meshing with the worm gear 144 on a shaft 146. The shaft 146 in turn carries a gear 148 which meshes with a gear 150 which is loosely mounted on the clutch shaft 58 and has formed on the face thereof the clutch member 136 previously referred to, to engage the corresponding clutch member 132 on the clutch shaft for driving the table.

Hand control means are provided for moving the clutch shaft 58 to connect the table to the hand or power feed and means are also provided which may be utilized when desired to automatically disconnect the power feed at the end of the table travel in either direction. This mechanism is fully described and illustrated in the applicants pending application above referred to, Serial No. 206,917, and need not here be described.

Several features of the present invention are directed to the provision of a simplified and improved cross feed mechanism for feeding the grinding wheel towards the work antomatically or by hand as the grinding opera tion progresses. The cross feed mechanism comprises a hand wheel for moving the wheel spindle carriage forward or back by hand and a power feed for advancing the wheel spindle -carriage in timed relation to the progress of the grindin operation on the work. With classes of work where the table is reciprocating the wheel spindle carriage is advanced slightly by the operation of the reversing mechanism at each end of the travel of the table. However, where the table is sta- .tionary, the rate of the power cross feed must be determined by some other standard, as for instance, by the rate of rotation of the work. The rate of rotation, however, varies widely in accordance with the setting of the hangs speed gearing for the headstock drive and one feature of the present invention consists in the provision of means for actuating the wheel spindle carriage cross feed from the head stock drive in timed relation to the rotation of the work and entirely independently of any variations in the setting of the change speed gearing which determines the rate of rotation of the work. Another feature of the invention in connection with the cross feed consists of m chanism mounted on a stationary and easily accessible portion of the machine for regulating the rate of the power cross feed in accordance with the nature of the work being operated upon. Other features consist in the provision of a simplified and improved control for throwing the hand and power feeds into and out of operation, and a caliper adjustment for setting the cross feed to turn the work down to size, which can be manipulated by the operator with a minimum of time and effort.

The mechanism for moving the grinding wheel towards and away from the work comprises a feed screw 220 (see 2) which extends toward the rear of the machine frame and engages with an internal thread in the bracket 224 on the wheel spindle carriage 26. On the forward end of the feed screw is secured a gear 226 which meshes with a pinion 228 formed on one end of a rotatable shaft 230 which also carries the hub of a spider 232 which is keyed to turn with the shaft. A hand wheel 234 is loosely mounted on the shaft 230 in front of the spider 232 and is normally connected to rotate therewith by means of the venier adjustment mechanism shortly to be described.

The automatic cross feed mechanism for rotating the spider 232 to advance the wheel by means of a spring 244. The pawl lever is loosely pivoted concentrically with the spider 232 and the hand wheel 234 and at its free end is connected by means of a link 246 to an actuating lever 248. This is in turn connected at its opposite end with a vertical bar 250 which is given a constant throw 7 of reciprocating movement to actuate the power feed.

In order to facilitate the adjustment of the rate of the power feed for the wheel spindle carriage in accordance with the nature of the work, the actuating lever 248 is provided with a fulcrum which is adjustable along the length of the lever to vary the throw given to the free end by the constant throw reciprocating movement of the vertical bar 250. The fulcrum comprises a block 252 which is pivotally mounted on an adjustable slide 254 and engages with a slot 256 formed in the lever. The position of the adjustable slide 254 which determines the effective throw of the lever 248 and the amount of the consequent rotation of the spider 232 for each feeding step is easily controlled by the operator from a knob or hand control 258 through connections '1 which include a shaft 260 and a pinion 262 on the shaft which engages a rack 264 formed on the under side of the adjustable slide 254. The knob 258 is slidably mountedto turn with the shaft 260 by a pin and slot connection and is held seated against a plate 265 by means of a compression spring 266 which is inserted between a shoulder on the knob and a shoulder on the shaft. The plate 265 is provided with a series of holes arranged to register with a pin 267 in the knob 258 so that the slide 254 is locked in adjusted position.

During the reciprocating movement of the work table, the vertical bar 250 is given a reciprocating movement to feed the wheel spindle slide automatically by means of connections from the reversing lever '98 which comprise a cam roll 268 mounted on the vertical bar 250 and the horizontal sliding bar 102 which is secured to the lower'end of the reversing lever and is provided with a cam tical bar 250 to maintain the relatively high position to which it is drawn by the action of a tension spring 270 stretched between the bar and a point on the machine frame. The

movement of .the reversing lever- 98 to reverse the direction of the table at the end of its travel in each direction causes the horizontal bar to move so that the roll 268 riding on the cam groove 269 is forced downwardly to depress the bar 250 against the pressure of its spring 270 and advances the wheel spindle slide a single step. The horizontal bar 102 then returns to its original position as the reversing lever is centered by the action of the load and fire mechanism, thus permitting the vertical bar 250 to rise again under the influence of its spring 27 O. In this manner, a step by step feed is obtained with each re verse in the direction of the table drive.

A reciprocating movement is imparted to the vertical bar 250 to obtain a power feed for the wheel spindle slide when the work table is not in motion by means of connece tions with the headstock drive which comprise a spiral gear 272 mounted on the shaft 218 for the headstock drive. This gear meshes with a corresponding gear 27 4 which is keyed to turn with a shaft 276 and is secured against end movement by abutting portions of the machine frame. 276 is adapted to move lengthwise and is provided with an eccentric 278 which in the forward position of the shaft 276 engages with a cam roll 280 mounted on the vertical bar 250. A hand knob 282 is provided on the forward end of the shaft to permit the operator to move the shaft forward or back to connect or disconnect the power cross feed with the headstock drive. A spring pressed The shaft detent 283 which is adapted to engage with one of the two recesses 284 formed in the shaft tends to hold the shaft adjustably in position. With this arrangement of the parts, a power feed is obtained for the wheel spindle carriage which is in timed relation to the rotation of the work under all conditions since any variation in the setting of'the change speed gearing in the head stock drive to vary the speed of rotation of the work will act through the connections above described to bring about a corresponding change in the rate of feed of the grinding wheel. A substantially constant ratio is thus maintained between the rate of advance of the grinding wheel and-the speed of rotation of thework under varying conditionsto produce the most efficient and satisfactory results in abrading or rinding down the surface of the work.

In the operation of both the hand and the power cross feeds for the wheel spindle carriage, it is-necessary to stop the feeding when the work has been brought down to size. In the present construction, this isaccomplished by means of stops mounted onthe hand wheel 234 which is normally fixed to rotate with the spider 232. The stop for the hand feed comprises an expansible block 286 which is clamped adjustably in position by means of a tightening screw 288 in a groove 290 in the periphery of the hand wheel 234. The block 286 cooperates with a control lever 289 provided with an abutment 291 with which the block engages as hereinafter described. A corresponding stop is provided for the power feed and comprises a plate 292 mounted on the hand wheel to engage with and disconnect the pawl 240 from the ratchet- 236 to disconnect the power feed.

Where the nature of the work requires the use of two or more grinding wheels of different diameters at the same time, itbecomes necessary to true these wheels relatively to each other as well as to secure a true surface on each wheel. \Vith the present construction, this may be done by the operator with a minimum of time and effort by the use of multiple stops which are most conveniently employed in connection with the hand feed. A number of stops such as those indicated at 294 and 296 similar to the stop 286 and corresponding to the additional number of wheel to be trued, are mounted in the groove 290 in the periphery of the hand wheel 234 and are spaced to permit the spindle wheel carriage to be fed towards the trueing tool and stopped in the positions required to maintain the proper difference in the diameters of the respective grinding wheels.

In order to permit the stops 286 and 292 to he set readily and accurately to cause the work to be brought down to the exact size desired. a novel and improved Vernier adjustment is provided for moving the hand wheel relatively to the spider to reset the stops after the work has been brought down approximately to size and the cross feed stopped with the stop 286 in engagement with the abutment 291. The Vernier adjustment comprises a small wheel 298 keyed to a shaft 300 rotatably mounted on the hand wheel 234 and provided at its inner end with a pinion 302 which engages gear teeth 304 formed on the outer periphery of the spider ring 238. The wheel 298 is provided with a spring pressed knob 306 which is adapted to fit into any one of a series of holes formed on a corresponding stationary plate 308 on the hand wheel 234 so that during the normal operation of the machine, the hand wheel and the spider will be held in fixed relation to each other. When it is desired to reset the stops 286 and 292 to permit the wheel spindle carriage to ad- Vance a certain definite amount, the knob 306 is lifted and the vernier wheel 298 is turned through a number of degrees marked on a graduated scale which correspond to the number of thousandths of an inch which remains to be taken off of the work when it is again secured by the knob 306. In order to permit the hand wheel to rotate freely with relation to the spider, the shaft 300 is adapted to be Withdrawn to disengage the pinion 302 from the gear teeth 304, a knurled head 310 being provided on the shaft 300.

A simplified and improved controlling mechanism has been provided to enable the operator more readily to throw the hand and power feeds for the wheel spindle carriage into and out of operation with a minimum of time and effort. The mechanism comprises a three-position lever which may be set for the power feed or the hand feed or in an intermediate neutral position to permit the operator to run the wheel spindle carriage by hand rapidly into or out of operating position.

The control lever is illustrated at 289 pivotally mounted at 312 on the machine frame and is provided with a handle 314. The up per end of the lever forms an abutment 291 which is adapted in one position of the lever to engage with the stop 286 for the hand feed. The lower end of the lever is provided with a cam roll 320 which rides on a cam surface 322 formed on the throw-out lever 324 for the power feed. This lever is pivotally mounted at 326 on the machine frame and is provided at its other end with a cam roll 328 which is adapted to come in contact with and disconnect the pawl 240 for the power feed. The cam surface 322 is held in contact with the roll 320 by means of a tension spring 330 which is stretched between the shoulder 332 on the control lever 289 and a point 334 on the throw-out lever 324. The cam surface 322 takes the form of three steps so that when the upper end of the control lever 289 occupies its inmost position in the path of the stop for the hand feed, the throw-out lever 324 will be depressed to disengage the power feed. In the neutral or intermediate position of the control lever 289, the upper end of the lever will be withdrawn from the path of the stop 286 for the hand feed and the roll 320 will occupy the intermediate step in the cam surface 322 with the power feed still disconnected, the contour of the cam surface and the tension spring 330 acting in conjunction to hold the parts yieldingly in position. The hand wheel may now be rotated at will by the operator to move the wheel spindle carriage rapidly into or out of operating position. In the third position of the control lever 289, the upper end of the lever will be withdrawn to its fullest extent and the cam roll 320 at the lower end of the lever will ride in the lowest portion of the cam surface 322, thus disengaging the throw-out lever 324 from the pawl 240, and throwing in the power feed.

It is desirable during the operation of the power feed to provide a friction device to prevent overthow of the cross feed mechanism in the step by step movement imparted by the pawl lever 242. In the present construction, this is accomplished by means of a brake arm 336 formed on the throw-out lever 324 which is drawn yieldingly into contact with the periphery of the hand wheel 234 by the tension spring 330 when the control lever 289 is positioned for the power feed.

The invention having been thus described, what is claimed is:

1. A grinding machine having, in combination, a grinding wheel, a longitudinally movable work table, a cross feed for the grinding wheel, automatic means controlled by the longitudinal travel of the work table for driving said cross feed, and a second automatic means acting in timed relation to the rotation of the work independently of the travel of the carriage for driving said cross feed to maintain at a substantially constant ratio the rate of advance of the grinding wheel with relation to the speed of rotation of the work.

2. A grinding machine having, in combination, a grinding wheel, a cross feed for the grinding wheel, a longitudinally movable work table, driving mechanism for the table, a reversing mechanism for imparting a reciprocating movement to the table from the driving mechanism, means for rotating the work, automatic means controlled by the table reversing mechanism for driving said cross feed, and a second automatic means driven by the work rotating means independently of the travel of the carriage for driving said cross feed to maintain at a substantially constant ratio the rate of advance of the grinding wheel with relation to the speed of rotation of the work. i

3. A grinding machine having, in combination, a grinding wheel, a wheel spindle carriage on which the grinding wheel is mounted, a work table, cross feed mechanism for moving the grinding wheel towards the work, means for rotating the work, and means actuated in timed relation to the rotation of the work to drive the cross feed to maintain at a substantially constant ratio the rate of advance of the grinding wheel with relation to the speed of rotation of the work.

4. A grinding machine having, in combination,a grinding wheel, a wheel spindle carriage on which the grinding wheel is mounted, a work table, cross feed mechanism for moving the grinding wheel towards the work, means for rotating the work, and means actuated by the work rotating means and in timed relation to therotation of the work to drive the cross feed to maintain at a substantially constant ratio the rate of advance of the grinding wheel with relation to the speed of rotation of the work.

5. A grinding machine having, in combination. a grinding wheel, a wheel spindle carriage on which the grinding wheel is mounted, a work table, cross feed mechanism for moving the grinding wheel towards the work, means for rotating the work, and connections actuated by the work rotating means for intermittently actuating the cross feed mechanism in timed relation to the rotation of the work to advance the grinding wheel at a rate to maintain at a substantially constant ratio the said rate of advance of the grinding wheel with relation to the speed of rotation of the work.

6. A grinding machine having, in combina tion, a grinding wheel, a longitudinally movable work table, driving mechanism for the table, a headstock and a footstock mounted thereon to support the work, means for rotating the headstock to rotate the work, reversing mechanism for the table, automatic means controlled by the reversing mechanism for actuating the cross feed, and a second automatic means actuated by the headstock rotating means for driving said cross feed to maintain at a substantially constant ratio the rate of advance of the grinding wheel with relation to the speed of rotation of the work.

7. A grinding machine having, in combination, a grinding wheel, a cross'feed for the grinding wheel, a ratchet wheel and pawl le- 1 ver for actuating the cross feed, an actuating lever for moving the pawl lever, and a fill? crum for the actuating lever adjustable to secure diflerent rates of feed.

8. A grinding machine having, in combi- Y nation, a grinding wheel, a cross feed'for the grinding wheel, automatic means for actuating the cross feed, an actuating lever through which the automatic means acts to feed the grinding wheel, and a fulcrum for the lever adjustable to secure different rates of feed.

9. A grinding machine having, in combination, a grinding wheel, a cross feed for the grinding wheel, automatic means for actuating the cross feed, a feed lever through which the automatic means acts to feed the grinding wheel, a fulcrum for the lever adjustable to secure difierent rates of feed, and graduated means for adjusting the position of the fulcrum.

10. A grinding machine having, in combination, a grinding wheel, a cross feed for the grinding wheel, a. ratchet wheel and pawl lever for actuating the cross feed, a power drive for the cross feed, an actuating lever through which the power drive operates to actuate the pawl lever, a fulcrum for the feed lever adjustable to secure different rates of feed, and a slide for the fulcrum mounted on the machine frame.

11. A grinding machine having, in combination, a grinding wheel, a cross feed for the grinding wheel, an internal ratchet wheel and pawl lever for actuating the cross feed,

a power drive for the cross feed, an actuating lever through which the power drive operates to actuate the pawl lever, slotted to permit adjustment of the fulcrum, a fulcrum block engaging the slot and slidably mounted in the machine frame, and means for adjusting the block to secure different rates of feed.

12. A grinding machine having, in combination, a grinding wheel, a longitudinally movable work table, a ratchet wheel and pawl lever for actuating the cross feed, a reciprocating member operatively connected therewith, automatic means controlled by the longitudinal travel of the work table for reciprocating said member longitudinally, and a second automatic means adapted to reciprocate the said member in timed relation to the rotation of the work to advance the grinding wheel at a rate to maintain at a substantially constant ratio said rate of advance of the grinding wheel with relation to the speed of rotation of the work.

13. A grinding machine having, in combination, a grinding wheel, a longitudinally movable work table, a reversing mechanism therefor, a ratchet wheel and pawl lever for actuating the cross feed, a feed lever for actuating the pawl lever, a reciprocating member operatively connected therewith, automatic means controlled by the reversing mechanism to reciprocate said member longitudinally, and means operative in the stationary position of the table to reciprocate the said member in timed relation to the rotation of the work to maintain at a substantially constant ratio the rate of advance of the grinding wheel with relation to the speed of rotation of the work.

14. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, a ratchet wheel and pawl lever for actuating the cross feed, automatic means for actuating the pawl lever, a hand wheel for operating the cross feed, and a manually operable cross feed control lever adapted in one position or" the lever to throw out the pawl lever and form a positive stop for the hand feed and in another position of the cross feed lever to permit the operation of the automatic cross feed.

15. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, a ratchet wheel and pawl lever for actuating the cross feed, automatic means for actuating the pawl lever, a hand wheel for actuating the ratchet wheel, and a manually operable cross feed control lever adapted in one position of the lever to disengage the pawl and ratchet and provide a positive stop for the hand wheel, in an intermediate position of the lever to remove the hand wheel stop while holding the pawl and ratchet in intermediate position and in a third position of the lever to permit the engagement or" the ratchet and pawl.

16. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, a ratchet wheel and pawl lever for actuating the cross feed, automatic means for actuating the pawl lever, a hand wheel for actuating the ratchet wheel, a friction brake for the cross feed, and a manually operable cross feed lever for simultaneously throwing the pawl and ratchet and the friction brake into and out of position.

17. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, means for manually operating the cross feed, automatic means for operating the cross feed, a friction brake to prevent overthrow of the cross feed mechanism, and means for moving the friction brake into and out of operation with the cross feed automatic operating means.

18. A, grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, an internal ratchet wheel operatively connected to the cross feed, a pawl lever actuated to give a step by step rotation to the rachet wheel, a hand wheel loosely mounted concentrically with the ratchet wheel and secured normally to move therewith, a stop on the hand wheel, and a micrometer adjustment for turning back the hand wheel relatively to the ratchet wheel to permit a further advance of the ratchet wheel and grinding wheel and cause the work to be ground to the required size.

19. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, a ratchet wheel and pawl lever for automatically driving the cross feed, a

hand wheel loosely mounted concentrically with the ratchet wheel and normally secured to move therewith, a stop on the hand wheel for the hand feed, a cam secured to the hand wheel for disengaging the automatic feed, and a micrometer adjustment for turning the hand wheel back with relation to the ratchet wheel scaled to indicate a corresponding advance of the grinding wheel to permit the work to be brought down to size.

20. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, a ratchet wheel and pawl lever for automatically driving the cross feed, a hand wheel loosely mounted concentrically with the ratchet wheel and normally secured to move therewith, multiple stops adjustably mounted on the hand wheel to stop the hand feed at different intervals, a cam secured to the hand wheel for disengaging the automatic feed, and a micrometer adjustment for turning the hand wheel back with relation to the ratchet wheel scaled to indicate the corresponding advance of the grinding wheel to permit the work to be brought accurately down to size.

21. A grinding machine having, in combination, a grinding wheel, a grinding wheel cross feed, a ratchet wheel and pawl lever for automatically driving the cross feed, a hand wheel loosely mounted concentrically with the ratchet wheel and normally secured to move therewith, a cam surface secured to the hand Wheel for disengaging the automatic feed, and a micrometer adjustment for turning the hand Wheel back With relation to the ratchet Wheel scaled to indicate the corresponding advance of the grinding wheel to permit the Work to be brought accurately down to size.

In testimony whereof I have signed my name to this specification.

MAXWVELL I. MATHEWSON.

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