US2277644A - Grinding and polishing machine - Google Patents

Description

March 24, 1942,

w. s. HOWE GRINDING AND POLISHING MACHINE Filed July 28, 1939 v 6 Sheets-Sheet 1 March 24, 1942. w. s. HOWE GRINDING AND romsnme MACHINE 6 Sheets-Sheet 2 Filed July 28, 1959 W. S. HOWE GRINDING AND POLISHING MACHINE Filed July 28, 1939 March 24, 1942.

6 Sheets-Sheet 3 March 24, 1942. w, s, HOWE GRINDING AND POLISHING MACHINE Filed July 28, 1939 Sheets-Sheet 4 GRINDING AND POLISHING MACHINE Filed July 28, 1939 I 6 Sheets-Sheet 5 March 24, 1942. w. s. H'OW E I GRINDING AND POLISHING MACHINE Filed JuIy 28, 1939 6 Sheets-Sheet 6 Ina/M1101 WM'J. M

Patented Mar. 24, 1942 2,277,644 GRINDING AND POLISHING MACHINE William S. Howe, Hinsdale, N. H.,

Production Machine Mass, a corporation of Massachusetts Application July 28, 1939, Serial No. 287,035 Claims. (01. 51-103) The present invention relates to grinding and polishing machines and more particularly to the so-called centreless type in which the work, instead of being mounted upon centres, rests upon a work support, rotating thereon under the combined influence of the grinding and polishing wheel engaging one side or face of the work and of the feed wheel engaging or face.

In such machines the longitudinal feed of the,

work is commonly obtained by giving a slight angular adjustment or tilt to the feed wheel so that the path of movement of the surface thereof across the periphery of the Work is inclined slightly to the plane of rotation of the grinding and polishing wheel. With such a construction the rate of feed may be varied by changing the angle of such inclination, the greater the angle the faster will be the rate of feed, and vice versa.

Since in such a construction the work is ordinarily arranged with its axis parallel to that of the grinding or polishing wheel, it is apparent that due to the inclination of the feed wheel to cause it to feed the work longitudinally past the polishing or grinding wheel, the contact of a cylindrical feed wheel with the cylindrical surface of the work will be not along a line or element of either wheel or work, but will be substantially at a point only. With such a small contact between the parts, the action of the feed wheel, which is primarily a braking or retarding action on the work to compel it to rotate at a peripheral speed much less than that of the grinding or polishing wheel, becomes uncertain, and the intended speed of rotation of the work may not be obtained and may vary from time to time with the result that the action of the grinding wheel becomes variable and uncertain and fine and perfect work is prevented.

In the endeavor to secure a line contact between the feed wheel and the work in order to provide sufficient surface to give perfect. and exact control of rotation of the work, it has been proposed to form the feed wheel with a contacting peripheral surface of the proper and exact concave shape. This, however, requires an exact shaping of the concavity in the feed wheel in accordance with the inclination of the feed wheel, so that for every change in the rate of feed there must be a new shaping or truing of the concave surface of the feed wheel.

The present invention seeks to avoid these ob jections and to provide a feeding element which shall be provided with a flat or plane surface traveling across the face of the work in a plane the opposite side assignor to Company, Greenfield,

:tangential to the work, so that irrespective of the diameter-of the work or the inclination of the path of movement of the surface of the feeding element, one and the same feeding device will always make a line contact with the work, thus giving perfect control of rotation of the latter ,and insuring the highest degree of accuracy in the grindingoperation. To the accomplishment of the above purpose the present invention contemplates a feed member comprising sections connected and arranged to form an endless belt, each section having a contacting face of rigid, unyielding material of such character as to control positively the rotation of the work. A satisfactory construction and arrangement is provided by the use of a flexible belt upon which blocks of abrasive material are secured. Another form comprises holders orcarriers pivotally connected together in link arrangement, each holder being provided with a .1 block of abrasive material securedthereto in a suitable manner. These abrasive blocks are provided with a flat or plane contacting face which ismaintained in proper shape and condition by a suitable truing device carried by the machine. The abrasive feed belt is driven by suitable mechanism, and a platen behind the belt opposite the point of contact with the work maintains the faces of the abrasive members in exact position for precision work.

In the accompanying drawings, Fig. 1 is aside elevation of a grinding machineembodying the present invention, and Fig. 2 is a front elevation of the same; Figs. 3 and 3a are side elevations, on an enlarged scale, of portions of two forms of the abrasive belt; Fig. 4 is a front elevation of one of such forms; Fig. 5 is a front elevation and Fig. 6 an end elevation of one of the abrasive elements of the other construction illustrated in Fig. 3, on a still larger scale; Figs. '7 and 8 are similar enlarged views of the form shown in Fig. 4; Figs. 9 and 10 show another form of abrasive element; Fig. 11' is a side elevation of a portion of the machine with parts broken away to illustrate more clearly certain mechanism; Fig. 12 is a fragmentary side elevation, partly. in section,

' scale; Fig. 13 is a front elevation, partly in secof a portion of such mechanism on an enlarged tion, of such portion; Fig. 14 is a horizontal sectional view on line X-X of Fig. 1 of a por- 'tion of the tilting head, platen, and platen actuating and locking mechanism onan enlarged scale; and Fig. 15 is a side elevation and Fig. 16 a front view showing the truing device for the abrasive belt. Fig. 17 is a part sectional view showing the feed belt tensioning mechanism and Fig. 18 is a sectional view taken on line itl8 of Fig. 17.

The grinding or polishing machine illustrated in Figs. 1 and 2 of the drawings is of a wellknown type, and comprises a grinding wheel 21 mounted upon the shaft 23, which is rotatably supported in the sleeve 25 carried by the arms 27 pivoted near their lower ends on the base 3| of the machine. The grinding wheel is belt driven from the power shaft 29. A protective hood or casing 33 encloses the wheel except at the front where the hood is cut away to permit the wheel to contact the Work. Upon the top of the casing is the truing device, indicated generally at 35, with the tool 3? adapted, when the device is tipped forward upon its pivot 39, to dress or true the face of the wheel 2| after the latter has been moved bodily back into its casing or hood to give space for the truing tool'between the wheel and the feed belt. The truing tool or atttachrnent is constructed and operated in general the same as shown in Fuller Patent No. 2,102,841, December 21, 1937.

To provide for bodily movement of the grinding wheel toward and from the feed belt, the left hand side wall of the casing, as shown in Fig. 11, has an elliptical opening 6! through which passes the bearing sleeve 25 for the wheel shaft. The right hand side of the casing, as shown in Fig. 1, is closed by a side plate 42 detachably secured thereto, such plate being provided with an elongated extension 43 to provide a space into which the end of the wheel shaft with the wheel securing devices extends.

The actuating devices for moving the wheel and its mounting comprise the hand wheel 45 fixed on an inclined shaft having at its lower end ,a screw connection with an extension on the lower projecting end ll of the supporting arm 21, this construction being the same as shown in said Fuller patent.

The locking means for locking the wheel mounting with the wheel in its forward or grinding\;position are shown in Figs. 11, 12 and 13 and comprise a clamping bolt or stud 5| mounted in the hood-supporting member 53 bolted to the base of the machine, with a spline or key to permit relative movement axially of the bolt. The headed end of the bolt extends through an arouate slot 55 formed in the pivoted arm 21 carrying the sleeve 25 which supports the grinding wheel shaft 23. The opposite end of the stud is externally threaded as at 5'1 and carries the nut or threaded sleeve 59 upon which is clamped the end of the actuating lever El. The adjustment of the locking nut or sleeve 59 on the threaded end of the bolt or stud 5| is such that when the actuating lever 8| is swung in a clockwise direction, the swinging arm 2! is clamped firmly against the fixed member .53 to hold the grinding wheel and its supporting mechanism. in

.fixed position. When the actuating arm BI is swung in a counterclockwise direction, the clamping nut is loosened and the swinging arms 21 are then free to be moved upon their pivotal supports to carry the grinding wheel either forward to its grinding or backward to its truing position.

The arm 6| is actuated by the operator by means of a, hand lever 63 clamped upon the horizontal shaft 65 mounted upon a bearing on the frame of the machine, which shaft also carries the arm 61 fixed thereon and connected at its upper end by the link 69 to the actuating arm 6 I. An adjustable stop screw H is. mounted in a web on the supporting member 53 in position to engage the lever SI and to prevent it from contacting with the main driving shaft 29. Normally, the lever 6| does not contact the stop screw H, the adjustment of the clamping sleeve or nut 59 on the bolt or stud 5| being such that 1e arm 2? is clamped securely against the fixed member 53' before the lever 6| reaches the stop H.

The feed unit comprises the endless abrasive feed belt 81 carried upon an upper and a lower roll or wheel 83 and 85, respectively, rotatably supported in the head 81 carried by the feed carriage 89, and arranged to be tilted laterally thereon about the horizontal bearing or support 59 to vary the rate of feed of the work. A clamping hand screw 9| passing through the slot -93 in the upstanding portion of the feed slide and threaded into the head 8'! secures the head in its adjusted tilting position upon the feed slide, the scale 94 indicating the extent or degree of tilt of the head.

Preferably, a second clamping or securing device is provided in the form of a headed bolt 95 passing through the slot 96 in the lower part of the upstanding portion of the feed slide and threaded into the tilting head 81 beneath the pivot 96. Ordinarily, the upper clamping hand screw 9i is sufiicient to hold the tilting head securely in its angular adjustment, the headed bolt d5 being tightened only enough to guide or support the lower part of the head without interfering with the tilting movement. If desired, however, the headed bolt 95 may be set up tightly with a wrench so that the head will be doubly secured in position.

The feed belt is driven from the power shaft through the pulley 97, belt 99, and pulley ml fixed upon the shaft of the speed reducing unit m3. From this unit, power is transmitted through the universal joints I05 and I0! and the telescoping connection I99 and worm and gear H! to the shaft H3 of the upper belt supporting roll or wheel 83.

The universal joints and the telescoping connection are required because of the necessity of adjusting the feed belt not only toward andfrom the grinding wheel to accommodate different diameters of work, but also at the proper angle or tilt to regulate the rate of feed. The adjustment toward and from the grinding wheel is acco plished by means of the hand wheel M5 on a threaded shaft 28! for moving the feed slide 89 upon suitable guides or ways on the feed slide support ill secured to the frame or base 34 of the machine.

In order to back up or support the feed belt opposite the work and grinding wheel, the tilting head 37 is provided with a platen I21 slidingly mounted in the head for movement toward and from the grindiz g wheel, but normally locked in its advanced or working position. The platen is formed with a shank or slide portion 523 which is mounted in a suitable guideway in the head 87. The end of this shank is provided with a rack l 25 engaged by a small segmental gear r26 on the shaft 52?. A handle @29 having the hub 13.0 on the shaft provides for the withdrawal of the platen away from the work and the grinding wheel when the lever is moved in a counterclockwise direction, as viewed in Fig. 1, by the operator. Movement of the platen towards the work is secured by means of a coil spring l3! surrounding the shaft IZI (see Fig. 14.), one end of which spring is fixed to the head 8'! while the other one is connectedto the sleeve I32, loose upon the end of the shaft. A tension adjusting screw I34 carried by the lateral extension I35 from the hub I3!) is arranged to engage the abutment arm I35 on the sleeve I32.

The above described construction and arrangement is such that the platen is normally urged toward the feed belt by the tension of the spring I3 I the amount of which may be varied by means of the adjusting screw I34. The platen may be retracted against the action of the tension spring by means of a backward or left hand movement of the handle I29, as viewed in Fig. l. A stud I31, extending into the side wall of th tilting head with its end extending into a slot I38 in the shank of the platen, limits the extent of movement of the platen toward and from the grinding wheel.

While under certain conditions of rough grinding and polishing it may be desirable to leave the platen under the control of the coiled spring so that the platen may yield, Without breaking, in case the work should present an abnormally high place, ordinarily the platen will be locked in fixed position by means of the threaded screw. Preferably, the end of the stud I31 is cone-shaped to extend into a correspondingly shaped recess I39 at the end of the slot 433 so that when the stud I31 is screwed inwardly by its winged head I30, the recess I39 Will center itself on such cone and the platen will be securely locked invariably in the same position. A knurled clamping nut MI is provided for locking the stud in position.

In order to secure the proper tension upon the feed belt when the machine is in operation, and to provide sufhcient slackness so that a belt may be removed from or placed upon the rolls or wheels 83 and 85, the upper'roll 83 is made adjustable in the tilting head 81 to permit movement toward and from the roll 85 mounted in fixed position in said head. Preferably, the upper roll 83 is yieldingly mounted so that it will automatically maintain the desired tension on the belt at all times when the belt is in operation, a compression spring acting to move this roll away from the fixed roll 35, but yielding to permit movement of the adjustable roll toward the fixed roll.

In the construction illustrated in the drawings, see Figs. 17 and 18, this is accomplished by mounting the bearing housing 2H for the shaft or spindle II3 of the upper roll 83 fixedly in the auxiliary slide 233 which is vertically movable upon the gibs or guideway 245 on the main slide 241, being supported thereon by the compression spring 249. A screw 25I extending upwardly through the lug or foot 253 on the main slide projects a short distance within the lower end of the coiled spring to maintain the latter in proper position. Thus, the upper roll 83 is free to'rise and fall upon or with respect to the main slide 241 by the expansion and compression of the supporting spring 2 39, as occasion may require.

The main slide 2 51, while normally held in fixed position upon the casing 261 of the tilting head 81, is vertically adjustable thereon. As shown in Fig. 17, an extension 255 is secured to the top of the main slide 241 by means of a bolt 251 and carries in the free end 259 a vertical threaded spindle MI having at its upper end the adjusting knob 263. The lower end of the spindle passes through a threaded opening in the shoulder or ear 265 extending laterally from the casing 261' of the tilting head.

not rotated, the main slide will be held in fixed position on the casing 261 of the tilting head 81. By rotation of the spindle 26 I, the main shaft I I3 may be raised or lowered, as desired, with respect to the tilting head, and when the main slide is raised, the spring 249 will be compressed and further tension given to the feed belt. On the other hand, if the main slide is lowered, the compression of spring 243 will be diminished and a corresponding decrease in the tension of the feed belt will result. If the main slide be lowered sufliciently through the rotation of the spindle 26I, all tension will be removed from the belt so that further rotation of the spindle will lower the upper roll 83. In this manner sufiicient clearance may be provided for the removal of the feed belt from the rolls for replacement or repair.

If the spindle 26I is so long that its end contacts with the bearing housing 24I before spring 2 19 is relieved of all compression, the continued lowering of the spindle will, by its abutting on the bearing housing, carry down with it such housing and the upper roll and other attached parts.

The spindle 26, in addition to its function of adjusting the spring 269 and of lowering the upper roll 83, has the additional function of limiting the upward movement of the bearing housing 24I and the upper roll under the action of spring 249.

By the above described arrangement with yieldingly raised upper roll 83, a uniform tension is maintained upon the feed belt. This is particularly advantageous where the machine is operating to do rough grinding and the platen I2I, instead of being locked on the head, is yieldingly pressed against the feed roll. If now an abnormally high place comes opposite the abrasive wheel or the feed belt, the platen may yield rearwardly and any slackness which tends to result from such rearward yield of the platen will be instantly taken up by the rise of the upper roll 83 under the action of spring 269; As soon as the high spot has passed and the platen moves back toward the abrasive wheel, the upper roll 83 will descend slightly against the compression of such spring. Thus provision is made for the yielding of the parts to avoid breakage or damage to them, while still maintaining the proper operative tension upon the belt.

In certain types of work where a plunge cut, so-called, is required, as where the surface to be ground or polished is of smaller diameter than the adjacent surfaces, it is of advantage to provide for the quick advance of the feed belt to- So long as the knob 263 and its spindle 23I are ward, and its withdrawal from, the work. This is accomplished by providing one of the bars, namely, 21I, upon which the feed carriage 83 is mounted to slide toward and from the work, with a series of rack teeth 213 engaged by a pinion 215 upon the inner end of short horizontal shaft 211, having fixed on its outer end the actuating handle 219. When this handle is actuated by the operator in a clockwise direction, as viewed in Fig. 1, the feed carriage will be advanced toward the work, and when the handle is turned in an anti-clockwise direction, the feed carriage is retracted.

In order to prevent the feed screw 28I of the feed carriage from' interfering with the quick advance and retraction of the carriage by the handle 219, the feed screw is rotatably mounted in a plain bearing on the rear of the table, through which the .screw or shaft has limited axial movement. The outward limit is determined by the flange 283 fixed on the shaft on the inner side of the bearing, and the inward limit by the stop collar 285 .adjustably mounted on the threaded outer end 281 of the shaft on the outer side of the bearing. By adjustment of the feed screw and stop collar any desiredlimit for the inward movement of the feed carriage may be obtained with a larger or smaller amplitude of movement as desired.

The work support consists of a narrow blade or plate N2 mounted upon the holder I43 on the arm or lever I45, pivoted midway its ends upon the stud I41 in the upper end of the lever I49.

This latter lever is carried upon parallel links I5I and I53, both pivoted to fixed parts of the machine. The link I53 is provided with a downward and from the grinding wheel, but to a lesser degree, and at the same time is raised and lowered so that the work support will be positioned to bring the axis of the work, whatever its diameter, into the same plane substantially normal to the surface of the grinding wheel at the point of contact.

In order to provide for finer adjustments'of the work support where, for example, a small diameter of the work is being ground, the end of the work supporting lever I is slotted and a clamp screw HSI provided which permits slight rotational movement of the work supporting lever I45 on its stud I41.

The endless abrasive belt with which this machine is provided comprises a series of blocks of abrasive material. These abrasive blocks may be constructed and connected in different ways; for example, as shown in Fig. 3, and in Figs. 5 and 6, the blocks I'II are fastened directly to a flexible belt or band H3 of metal or other suitable material by means of bolts I'i5 having their heads embodied in the abrasive material when the blocks are formed by casting, and with their threaded ends passing through openings in the band with nuts IT! on such ends. Preferably, the abrasive blocks are formed with interlocking inclined edges, i. e. V-shaped as shown at I19 and Iil, to avoid any objectionable gap being formed between adjacent blocks which might cause a pounding action as the joints passed across the work, with consequent impairment in the operation of the machine.

While such a belt may be driven merely by frictional contact with a driving roll or wheel in the tilting head, preferably it is positively driven by means of teeth formed on the driving roll or wheel which engage suitably positioned driving members on the inner face of the band. Such a construction is illustrated in Figs. 9 and 10, where the abrasive blocks are mounted upon carriers or supports I35, having on their inner faces a roll IBI pivotally mounted in the brackets I88.

Still another form of lag belt construction is shown in Fig. 3a and in Figs. 4, 7 and '8, where carriers or supports for the abrasive blocks are provided with laterally extendingpins or studs I9I having a groove I93 adjacent their ends. 'The blocks are connected together to form an endless lag belt by means of side bars or links I95 with the internally recessed ends I91 retained on the pins by the well known groove and spring ring construction. Such a link belt is driven by the upstanding teeth I99 on the periphery of the driving roll or wheel, which teeth extend into recesses 2! in the bottom or inner faces of the carriers for the abrasive blocks.

The truing device or dresser for the abrasive blocks, as shown in Figs. 15 and 16, comprises a rotarygrinding tool 293 mounted upon the shaft extension of the electric motor 265, which is fixed upon a base or support having a dovetail guideway upon the dovetail or guide 201 of the dresser for the grinding wheel, being interchangeable therewith when it is desired to true the faces of the abrasive blocks. At such times the support for the truing device is swung forwardly into the position shown in Figs. 15 and 16, and carried across the face of the abrasive blocks by means of the feed handle 2 while the feed belt is being driven in its normal manner. When not in use, the truing device with the wheel truing tool or the belt grinding tool will be tipped backwardly on the hood of the Wheel, as shown in Fig. l, where it will be out of the way during the regular grinding operations.

By the use of these link belts formed with the plane feed surface of hard abrasive material, the work is controlled in an exact and positive manner, the abrasive material with its line contact on the work giving it a certain and secure grip on the work so that the rotation of the same is always at the desired speed. The abrasive blocks, having a substantial thickness, provide for long and continued use before they are so reduced in thickness by wear as to require replacement, and throughout such use the same sharp, abrasive surface is always presented to the work with no loss of effectiveness in controlling the rotation and feed thereof. Furthermore, such blocks, being rigid and unyielding, and being backed up by the platen, cause the work to be definitely and exactly presented to the grinding wheel. As a result, more exact and perfect grinding may be secured than with prior constructions, and no re-shaping or facing of the feed element is required for changes in diameter of the work or the rate of feed.

While in the accompanying drawings and in the foregoing specification a preferred embodiment of the present invention has been shown and described, it is to be understood that the invention is not limited thereto but may be embodied in many other forms and arrangements, and the various parts thereof may be changed .in their form and design, all within the language of the claims.

Having thus described the invention, what is claimed is:

1. In a centreless grinding machine, the combination with a rotating grinding wheel, of a feed belt for engaging the work on the opposite side thereof from the grinding wheel to control the rotation of the work, a work support located between the wheel and the belt for supporting the rotating work, supporting devices for the belt, and means for driving the belt at a substantially less lineal speed than the peripheral speed of the grinder, the feed belt comprising an endless series of separate feeding elements angularly movable with respect to one another to permit flexing of the belt on the supporting devices, each element being provided with a flat, work engaging face of rigidly held abrasive material.

2. In a grinding or polishing machine, a rotating wheel for operating on the work, a feed belt, means for actuating the wheel and belt, a platen for the belt on the-opposite side thereof from the wheel, means for moving the platen toward and from the belt and wheel comprising a rack connected to the platen, a gear engaging the rack, a coiled spring for rotating the gear in a direction to move the platen toward the belt and wheel, and an operating handle connected with the gear for rotating the same.

3. In a grinding or polishing machine, a rotating wheel for operating upon the Work, a feed belt, means for supporting and actuating the wheel and belt, a platen for the belt on the opposite side thereof from the wheel, means independent of the belt supporting means for moving the platen toward and from the belt and wheel, and locking devices including a conical ended recess and a longitudinally movable conical ended member arranged to enter the recess with the end of the member positioned in the end of the recess to lock the platen in a predetermined position.

4. In a grinding or polishing machine, a rotating wheel for operating upon the work, a. feed belt, means for actuating the wheel and belt, spaced rolls for supporting the belt, one of said rolls being spring mounted to maintain the desired tension on the belt, and a platen for the belt positioned opposite the rotating wheel and adjustable toward and from the wheel independently of the belt supporting rolls.

5. In a grinding or polishing machine, a rotating wheel for operating on the work, a feed belt, means for actuating the wheel and belt, a platen for the belt on the opposite side thereof from the wheel, yielding means for urging the platen toward the belt, and spaced rolls for supporting the belt, one of said rolls being spring mounted to maintain the desired tension on the belt irrespective of the deflection of the belt by the platen.

6. In a grinding or polishing machine, a rotating wheel for operating upon the work, a feed belt, means for actuating the wheel and belt, a carriage for the belt, a feed screw for adjusting the carriage toward and from the work, and means, including a rack and a pinion for quick adjustment of the carriage toward and from the work.

7. In a grinding machine, the combination with a rotating grinding wheel of a feed belt for engaging the work on the opposite side thereof from the grinding wheel to control the rotation of the work, a work sup-port located between the wheel and belt for rotatably supporting the work, supporting devices for the belt to cause its work contacting portions to travel in linear paths inclined to the plane of rotation of the wheel to feed the work, and means for driving the belt at a substantially less linear speed than the peripheral speed of the grinding wheel, the feed belt comprising a flexible band and a series of work feeding elements of fiat, rigid, abrasive material secured to the face of the band.

8. In a grinding machine, the combination with a rotating grinding wheel of a feed belt for engaging the work on the opposite side thereof from the grinding wheel to control the rotation of the work, a work support located between the wheel and the belt for rotatably supporting the work, spaced rolls for supporting the belt to cause it to travel in a plane inclined to the plane of rotation of the wheel to feed the work, and means for driving the belt at a substantially less linear speed than the peripheral speed of the grinding wheel, the feed belt comprising an endless series of work feeding elements having flat, rigid, work engaging abrasive faces, and pivoted links connecting adjacent elements.

9. In a grinding machine, the combination with a rotating grinding wheel of a feed belt for engaging the work on the opposite side thereof from the grinding wheel to control the rotation of the work, a work support located between the wheel and the belt for rotatably supporting the work, spaced rolls for supporting the belt to cause it to travel in a plane inclined to the plane of rotation of the wheel to feed the work, means for driving the belt at a substantially less linear speed than the peripheral speed of the grinding wheel, the feed belt comprising an endless series of separate feeding elements angularly movable with respect to one another to permit flexing of the belt on the supporting rolls, and means on the faces of the elements opopsite the, work engaging faces for positively actuating the belt.

10. In a grinding machine, the combination with a rotating grinding wheel of a feed belt for engaging the work on the opposite side thereof from the grinding wheel to control the rotation of the work, a work support located between the wheel and the belt for rotatably supporting the work, spaced rolls for supporting the belt to cause it to travel in a plane inclined to the plane of engaging faces of rigid abrasive material the contiguous edges of such material on adjacent elements being inclined with respect to the path of movement, such elements providing continuous feeding movement to the belt.

WILLIAM s. HOWE.

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