US2252176A - Machine for grinding cylindrical surfaces - Google Patents

Description

Aug. 12, 1941. W. H. HARRIS, JR 2,252,176

MACHINE FOR GRINDING CYLINDRICAL SURFACES Original Filed Dec. 19, 1936 4 Sheets-Sheet- 1 I INVENTOR. n ZZZZdm Harris, 7;?

ATTORNEYS.

I Aug. 12, 1941.

w. H. HARRIS, JR 2,252,176 MACHINE FOR GRINDING GYLINDRIGAL SURFACES Original Filed Dec. 19, 19:56 4 Sheets-Sheet 2 INVENTOR. BY m llz'dm Hay-x715, J7

ATTORNEYS.

Aug. 12, 1941. w. H. HARRIS, JR

MACHINE FOR GRINDING CYLINDRICAL SURFACES Original Filel Dc. 19, 1936 4 Sheets-Sheet 4 Z 2.. 2 M 9 A. W

INVENTOR.

146222142 fi/V rrz ATTORNEYS.

Patented Aug. 12, 1941 om son ammo CYLINDBICAL summons William 11. Harris, in, Detroit, men, asllgnor to Micromatic Hone Corporation, Detroit, Mich, a corporation of Michigan Application December 19, 19st, Serial No. 116,774

Renewed November 15, 1939 12 Claims.

My invention relates to grinding and honing devices and methods and particularly to a machine and method for accurately and rapidly finishing the inside surface of a cylinder.

.It was the practice heretofore to finish cylinders by a honing method wherein the honing tool. was reciprocated during the time it was rotated. Therelative speed of reciprocation. and rotation varied, depending upon the length of stroke and v the peripherial dimension of the tool. The

length ofv stroke varied to conform with the length of the work piece and could be considered as the feed movement between the work and tool. Such a tool is illustrated and described in the F. J'. Jeschke Patent No. 1,944,660 which was assigned to the assignee of thepresent invention.

A method has been evolved for materially improving and standardizing the finishes on the internal surfaces of cylinders by selecting proper ratios between the degree and speed of reciprocation relative to the peripheral speed of rotation of the grinding tool, which ratio may vary, depending upon the type of material which is being operated upon. -In addition to these motions in reciprocation and rotation, a relative feed motion is provided between the work and the tool. This method and apparatus for practicing the method is disclosed in the K. W, Connor application for Letters Patent, Serial No, 16,519, filed April 27, 1936, which has become Pat. No. 2,108,029 and assigned to the assignee of the present invention. v

In practicing th present invention, I employ vide the proper ratio between the peripheral speed and the speed and degree of reciprocation. Means are provided for feedingthe work over the abrading head during the time the head is reciprocating and rotating intimed relation.

To permit the insertion and removal of the work piece over and from the abrading head, the machine is provlded'with a lever for operating a clutch and brake for stopping the rotation of the head and for simultaneously operating means for electing its collapse. This permits the work to be removed without engaging the abrading elements and a new work piece to be inserted over Unique means are provided for producing the reciprocation of the abrading head which may be varied from substantially zero to extremely high Thisiseflcctedbytheuseofapair of pulleys which may be driven at different speeds to produce reciprocation through a wobble plate connection therebetween. By varying the speeds of the pulleys, the speed of reciprocation may be varied.

Accordingly, the main objects of my invention are to provide a machine which accuratelyand rapidly machines a very high polish to the internal surface of a cylinder; tointernally finish a cylindrical member by a machine having a reciprocable abrading head which is rotated in timed relation to the speed of reciprocation; to provide a pair of pulleys which are driven at different speeds with a wobble plate connection for producing the reciprocation of the abrading head which may be varied by changing the relative speeds of the pulleys; to provide a means for collapsing the abrading head preferably at the time when the machine is stopped to permit the work piece to be removed and a new work piece to be inserted over the head which is expanded when the machine is again operated; to provide clutches for controlling the operation ,of the head in rotation and reciprocation and a brake for stopping the rotation of the head immediatelY principles set forth in the above applications in upon its disconnection from the driving means; to provide an element in combination with the abrading head which is reciprocable between stops to regulate the degree of relative feed movement between the work piece and the abrading-head; and, in general, to provide a machine and method for accurately and rapidly finishing the internal surfaoesof a cylindrical element which is rugged in construction, positive in operation, and economical of manufacture.

Other objects and features ot'novelty of my invention will be either specifically pointed out or will becom apparent when referring, for a better understanding of my invention, to the following description taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a'plan view of a'machine embodying features-of my invention, with the cover re- I moved therefrom:

Fig. 2 is a reduced view, in perspective, oi the machine illustrated in Pig. 1, with the cover at tached thereto;

Fig. .3 is an enlarged sectional view or one-half of thetool illustrated in Fig. 1, taken on the line l-lthereoi,fromthefrontendtothe eecilon liner-hereof;

Fig. 4 is an enlarged Sectional view of the rear half of the tool illustrated in Fig. 1, taken on the line 44 thereof from the section line :r-x to the rear end of the tool;

Fig. 5 is an enlarged sectional view of the structure illustrated in Fig. 3, taken on the line 55 thereof;

Fig. 6 is an enlarged sectional view of the structure illustrated in Fig. 3, takenon the line 66 thereof;

Fig. 7 is a sectional view of th structure illustrated in Fig. 1, taken on the line '|-'I thereof;

Fig. 8 is an enlarged broken sectional view of the structure illustrated in Fig. '7, taken on the line 8-8 thereof, and

Fig. 9 is a broken view, in section, similar to that illustrated in Fig. 4, showing a modifiedform thereof.

In the drawings, a machine I is illustrated asbeing of the table or bench type to be employed for machining work pieces having small internal diameters. It is to be understood that this type of machine is shown for the purposeof illustration and that similar structure and methods of operation may be utilized in larger and heavier machines built on bases which rest'directly upon the floor. A base supports a motor l2 and a honing or grinding device l3. The motor I2 is herein illustrated as resting directly upon the base and is bolted or otherwise secured thereto. The tool I3 is herein illustrated as being built on projections extending from and forming part of the base. It is to be understood that the tool itself may be a separate unit to be supported on the base in predetermined relation with the motor.

In the structure illustrated, the base II has a pair of bosses I4 and I5 projecting upwardly therefrom in aligned relation. Suitable strengthening webs l6 may be utilized for further strengthening the bosses and the bed. A shaft I1 is disposed through an aperture I8 inthebearing. boss l5, the shaft being provided with suitable oil grooves l9 through which the engaging surfaces are lubricated.

The shaft has a pulley 2| secured thereto by a pin 22, or other means well known in the art to be suitable, extending through a frontwardly projecting boss 23 on the pulley. A rearwardly extending boss 24 on the pulley supports a thrust bearing 25, the front race 26 of which carries a sleeve 21 over which a spring 28 is positioned to bear against the race 26 with the opposite end of the spring projecting over a shoulder extension 29 of the bearing boss I 5. A thrust is thereby provided to the shaft I9 to the right, as viewed in the figure.

The right hand end of the shaft |9 has a reduced portion 3| which engages needle bearings 32 encased in the end of a sleeve 33 which is provided with an aperture 34 in the bearing boss M. The needle bearings 32 are retained against axial movement within the recess in the end of the sleeve 33 by an end washer 35 secured thereto by one or a plurality of screws 36. The outer surface of the sleeve 33, diametrically disposed to the inner surface containing the needle bearings 32, forms a race-way for a series of needle bearings 31. The needle bearings 31 are encompassed by the'inner surface of a projecting boss 38 on a sec- 0nd pulley 39. The pulley 39 is herein illustrated as being of the same diameter as the pulley 2|- but it is to be understood that the diameters-may vary relative to each other depending upon the once, the shaft 38 will be reciprocated nine times.

which is slidably disposed in engagement with screws 44. The pulley 2| is provided with a finger secured thereto by a threaded extension 46. The projecting end 41 of the finger engages an aperture 48 in the top raceway 49 of the thrust bearing 42.

In the structure thus far described, the shaft I! is supported for rotation in the aperture l8 of the bearing boss |5 with its rear end supported by the needle bearings 4| .within the sleeve 43. The rotation of the shaft is produced through'the op eration of the motor l2 driving a belt 5| through a pulley 52 mounted on the motor shaft. The pulley 39 which is rotatably supported on the needle bearings 31, is supported against axial movement by a thrust bearing 53 which is disposed between the bearing boss l4 and the boss 38 of the pulley. The pulley 39 is driven in rotation by a belt 54 from a pulley 55 which is herein illustrated as being of less diameter than the pulley 52 which drives thepulley 2|. As a result, the pulleys 2| and 39 are rotated at different speeds causing a relative movement to occur between the finger 45 and the pulley 39. As a result of the relative travel between the finger and pulley, the pulleys will be moved apart against the tension of the spring 28 as the finger 45 moves from one position of the tilted race 49 to another position thereof. It will thus be seen that the relative driving speeds of the pulleys 2| and 38 is very important in producing the proper speed of reciprocation to the shaft 28. If the pulley 2| is rotated ten times while the pulley 39 is retained stationary, the shaft would be reciprocated ten times. If, however, the pulley 2| is rotated ten times, while the pulley 39 is rotated If the pulley 2| is rotated tentimes while the pulley 39 is rotated five times, the shaft will reciprocate five times. I

By mounting the bearing 42 in the pulley 39 in 'such a manner that it may be tilted at various angles relative to the face thereof as illustrated in Fig. 9, the degree of reciprocation may likewise be varied at will. The adjustment is effected through the manipulation of the screws 40.

The bearing boss |5 has a reservoir 55 disposed in aligned relation with the aperture |8 communicating with a filling passage 56. A recess 61 is provided on the shaft over which a ring 58 extends to provide lubrication to the oil grooves in a well known manner. Annular grooves 59 are provided at each end of the shaft within the confines of the aperture l8 to seal the surface of the shaft against the egress of lubricant.

The left-hand end of the shaft I1, as viewed in Fig. 3, has a collar-6| threaded thereon and retained in position by a locking nut 62. The collar abuts against a hollow spindle 63 having anvenlarged end 64, the outer surface of which is threaded. A tool spindle 65 is slidably disposed within the spindle 63 and extends forwardly a considerable distance from its front end. A pin 61 is carried by the tool spindle 65 projecting through a slot 66 in the wall of the spindle 63. The pin 61 engages and supports a sleeve 68 the outer surface of the spindle 63. A spring 69 is disposed-between the enlarged end 64 of the spindle 63 and a shoulder on the end of sleeve 68.

desired speed of reciprocation of the shaft. The

Encompassing the spindle 63 at its front end is 2,292,176 a housing'II of annular shape having projecting extensions I2 in cylindrical alignment with the front end, which projections are joined to an annular flange whichmates with a flanged extension I3 of the bearing boss I5 and secured thereto by a plurality of screws I4. The openings 5 between the projecting extensions 12 permit access to an adjustingsleeve IS on the tool.

- The collar 9| on the end of the-shaft II forms a portion of a roller thrust bearingwith an element I9 which is provided with a collar 11' having a plurality of cam surfaces I9 thereon. The.

rear end of the spindle 53 carries a slidable sleeve II having a shoulder 92 at its forward end and a thread on the outer surface of its opposite end.

A threaded sleeve 93 encompasses the sleeve II and forms therewith a double ball race which is assembled by means of a nut'94 retained by a locking nut 95 disposed on the threads of the sleeve 92. The outer surface of the sleeve 93 is provided with threads over which the adjusting nut 19 is threaded. A plurality of recesses 85 are disposed in the end face of a collar 81 having complementary cam faces in engagement with the cam faces I9 on the collar I9. A spring pressed ball 99 carried by the nut I6, engages one of the plurality of the recesses to lock the nut relative to the collar 91 while permitting its adjustment relative thereto. A split spring locking element 88 prevents the movement of the adlusting nut I6 beyond a predetermined point. The sleeve 8| has a pin 99 projecting therethrough and through slots Si in the sleeve 63. The pin engages a nut 92 screwed on the end of a plunger 93 having a head 94 on its forward end. A suitable locking nut 95 secures the nut 92 in fixed ad- .iusted position on the plunger 93. A sleeve 95 has sliding engagement with the plunger 93 and has a flanged end 91 in engagement with the end of the tool spindle 55. A spring 99 encompasses the plunger 93 and sleeve 96 and extends between the flange 91 and the locking nut 95. Through the adjustment of the hand nut 19, the position- -of the tool spindle 95 relative tothe spindle 93 is determined. Such adjustment moves the sleeve II and the pin 99. The change in the position of the pin 99 adjusts the plunger 93 and positions the spindle 65 through the sleeve 96.

purpose of adjusting the abrading head in expansion and retraction. The front portions of the slide I99 form stone carriers I99, while the rear end has projections I99 which are secured to the end of the spindle" by an end cap III secured to the enlarged end 54 thereof. A split annular or garter spring I I2 may be employed to retain the end projections in position.

In operation, the carriers I99 are retainedagainst longitudinal movement while the tool spindle 95 is moved axially which, in view of the sloping surfaces, moves the carrier outwardly to expand the tool when the spindle 95 is moved to the left as viewed in the figure. When the spindle is moved to the opposite direction, the action of thesloping surfaces permits the carriers to move radially inwardly to thereby reduce the diameter of the honing head.

, Suitable abrading elements II3 are secured to the carriers I99, the ends of which are drawn radially inwardby a garter spring II4 projecting over hooked lugs I I5 provided on the ends of the carriers.

Slidably disposed over the housing II is a sleeve H5 having an end cap I" threaded on its front end. A sleeve H9 is also secured to and carried by the gap II'I- disposed internally of the housend of the spring contacting a flange I22 on the housing II. The spring tends to move the two sleeves H9 and H9 forwardly along with the cap The collar 11 is provided with a lug as to which an adjustable link 99 is pivoted. The link is. connected to arm IN on a bell crank I92 which is pinned to a shaft I93, as illustrated more clearly in Fig. 1. When the bell crank is rotated clockwise to-move the link 99 toward the bottom of the drawing as viewed in Fig. 1, the

- collar I3 rotates in counter-clockwise direction causing the cam surfaces I9 thereofoperating on the cam surfaces on the collar 91 to force the collar 91 toward the front of the tool. This will move the sleeve III and pin 99 frontwardly to move the plunger 93along therewith. This movement of the plunger releases the support of the head 94 from the sleeve 91 which will then load the tool spindle 64 because-of the presence of the tension in the spring 98. The bias thus provided to the spindle will cause the spindle to move forwardly, which movement is opposed by the weaker spring 69 operating on the sleeve 59 to which the pin- 9|, carried by thespindle 65, is secured- Suitable means, such as a split annular spring, a garter spring or the like I94, may be employed to retain the pin 51 in position rCative to' the sleeve 59.

The front end' of the spindle 95 ishereln illustrated as being provided with a plurality of T III. For regulating the degree of movement and to position such movement relative to the tool head, I have provided a gauge comprising a thread stem I23 bolted or otherwise secured to the pro- 'jection portion I2 of the housing II by screws I24. Two sets of thumb nuts I25 are disposed on' the stem I23, each pair being spaced from each other an amount equal to the desired limit of reciprocation of the cap H1. The nutsmay be adjusted, when regulating the degree of reciprocation, to position the point where the reciprocation of the cap III occurs relative to the abrading tool. A-stud I29 projects from the sleeve I I9 directly adjacent to the stem I23 between the nuts I25. The stud I29 acting between the nuts I25 limits the degree of reciprocation to the cap I". A slot I2! is provided in the sleeve IIS and also in the end ofv the housing 'II. A tube I29 is carried by the sleeve II9 projecting into the slot I21.

A coolant is delivered through the tube I29 di rectly adjacent to the cap I I9 and a central aperture- I39 provided therein through which the spindle extends. The purpose of the cap I" is to provide a means for assisting the operator in holding and feeding the work piece over the abrading head. The adjustable stop prevents the the position shown, the collar is moved to the right over the abrading elements II3 limited by the engagement of the stud I23 with the right hand pair of nuts I25. The operator releases the pressure on the work piece to permit the spring I2I to force the work piece in the opposite direction limited by the engagement of the stud I25 against the left hand pair of nuts I25. In this manner, the feeding of the work piece over the elements H3 is very accurately adjusted.

Referring to Figs. 1, 7 and 8, I have illustrated the clutch and brake mechanism which controls the starting and stopping of the tool. The motor I2 is provided with ashaft I33 upon the end of which a clutch plate I34 is secured, preferably by a set screw I35. The front end ofthe plate is 4 provided with a hub I33 having oil grooves I33 therein and over which a cylinder I3! is disposed. The pulleys5i and 52 are secured tothe cylinder I31 with the end face I33 of the pulley 52 slightly spaced from the clutch plate I34. The cylinder I3! is provided with a head I39 carrying a spring pressed ball I in its end. The ball is disposed to contact a sloping surface I42 provided on a cam lever I43 which is pinned to the shaft I03.

The cam plate I 43 has a projection I 44 which is disposed adjacent to the hub 33 of the pulley 39.

The projection I44 is provided with a brake material I45 to form a brake shoe of a contour to engage the outer surface of the hub 33. An arm I46 of the bell crank I02 is connected to a link I" which is secured to a foot treadle I43 for controlling the operation of the shaft I03.

position of the flange 9'! relative to the spindle 45. When the collar I1 is rotated, the cam surfaces I9 move the collar 31 to the left, as viewed in Fig. 3, which movement causes a similar movement of the pin 39 and the plunger 93 and places a direct bias of the spring 93 against thespindle 35 and the retrieving spring 39. The adjustment may be such that the abrading elements will en-.

gage the inner surface of the work piece I3I while the flange 91 is slightly spaced from the head 34 of the plunger 93 to permit a feed movement of the elements II3 outwardly until the flange 31 engages the head 94. A proper diameter should then be provided to the work piece. The diameter may be changed in this manner and may be corrected as the elements II3 wear.

A coolant is delivered through the tube I23 directly adjacent to the point of contact between the abrading elements I I3 and the work piece I3I A receptacle I4! is provided below the abrading head of the tool to receive the coolant. The coolant may be delivered to a suitable reservoir from which it may be pumped through a conduit I43 When the treadle is moved down toward the floor, the bell crank is moved inclockwise direction rotating the collar 13 in counter-clockwise direction to produce the extension of the collar 31 and, therefore, the tool spindle 65 which affects the expansion of the elements H3. The movement of the bell crank in this manner causes the shaft I03 to also move in a clockwise direction moving the brake shoe I out of contact with the hub 33 and the cam surface I42 into engagement with the ball I on the head I39. The engagement of the surface I42 with the ball I4I moves the cylinder I31 and pulleys 5| and 52 to the left, as viewed in Fig. 8-, causing the surface I33 to frictionally engage the clutch plate I34.

This produces a driving connection between the shaft I33 of the motor and the pulleys.

Upon releasing the foot treadle I43, the link I4'I will be raised by the spring I49 moving the bell crank in-a counter-clockwise direction and the collar I3 in clockwise direction. This moves the collar 3'! and spindle 65 to the right, thereby collapsing the abrading head by permitting the elements II3 to move radially inwardly. The

counterclockwise movement of the bell crank I02, the shaft I03 and cam plate I 43, moves the cam surface I42 out of engagement with the ball I and permits the cam surface I33 to disengage the cam plate I34. Further movement of the cam plate I43 causes the brake shoe I45 to engage the hub 33. The abradinghead will cease rotation instantly and, since the abrading head has been collapsed, the work may be removed without contacting the abrading elements II3. A new work piece may then be inserted over the abrading elements and the abrading head operated in rotation and reciprocation through the movement of the foot treadle I43.

As the abrading elements II3 wear, because of repeated abrading operations. they may be adjusted radially through the operation of the adlusting nut I3 which moves the pin 33 relative to the tube I23. The conduit is flexible to permit the movement of the tube with the cap III.

In Fig. 2, I have illustrated a cover I49 which encloses the motor and the rear portion of the tool. It is to be understood that the machine thus described is utilized for machining small work pieces. Such work pieces may be grasped in the fingers of an operator and moved over the abrading head while engaging the cap I" and slowly feed back and forth during the time the abrading head is rapidly reciprocating and rotating.

On similar machines or machines for operating on large work pieces, a mechanical feeding device may be employed which may be automatic. A receptacle may be employed for receiving the work piece and moving it along the abrading head between predetermined limits. After a predetermined number of cycles of movement, the machine may be automatically stopped, at which time the work piece can be removed. It is also within the purview of my invention to employ automatically operating means for contracting the abrading elements after the machine operation which functions upon the insertion of a new work piecein the feeding device to expand the abrading elements and start the machining operation.

While I have illustrated and described but a single embodiment of my invention, it will be apchangeaadditions, omissions and substitutions to the camming surface 13 to thereby regulate the may be made therein without departing from the spirit and scope of-my invention'as set forth in the accompanying claims.

I claim as my invention:

1. A grinding machine including, in combination, a base, a spindle rotatable thereon, means for rotating and reciprocating said spindle in timed relation, an abrading head carried by said spindle, abrading elements in said head, means for adjusting said abrading elements to a desired diameter, means for expanding and retracting said abrading elements in said head, and means for retracting said abrading elements and for simultaneously stopping the rotation of said spindle.

2. A grinding machine including, in combination, a base, a spindle rotatable thereon, means for rotating and reciprocating said spindle in timed relation, an abrading head carried by said spindle, abrading elements in said head, means for adjusting saidabrading elements to a desired diameter, means for expanding and retracting spindle, an additional pulley mounted adjacent to said first pulley and rotatable independent thereof, a swash plate carried by one of said pulleys, projecting means-carried by said other pulley contacting said swash plate, a spring urging said contacting means toward said swash head carried by said spindle, means for controlling the feed oi the-work piece relative to said abrading headduring the time it is reciprocating and rotating, and means for delivering a coolant to said abrading head carried by said feed control means which'encompasses the endo! said delivery means.

4. A machine for grinding a work piece including, in combination, a spindle, means for rotating and reciprocating said spindle, an abrading head ing and contracting said abrading head, and a carried thereby, means for expanding and contracting said abrasive head, means providing a limited teed movement to said abrading headto .permit its expansion during the time it is reciprocating and rotating and means encompassing said spindle for controlling the feed of a work piece bver said abrading head during the time it is reciprocated and rotated.

5. A grinding machine including, in combination, a rotatable spindle, a plurality of tapered slots in said spindle, carriers in said slots having tapered surfaces mated with those of said slots, means for retaining said carriers against longitudinal movement, and means for moving said spindle longitudinally to eiiect the contraction and expansion of said carriers.

6. A machine tool including, in combination, a rotatable spindle provided with a plurality of slots having sloping surfaces, a plurality of stoneholders having sloping surfaces mateable with those in said slots, means for retaining said holdera against longitudinal movement, means ior biasing said holders into said slots, and means tor moving said spindle longitudinally to effect the contraction and expansion of said holders.

I. A machine tool including, incombination, a

rotatable spindle, a driving pulley secured to said spindle, an additional pulley mounted adjacent to said first pulley and rotatable independently thereof, a swash plate carried by one of 'said pulleys, projecting means carried by said other pulley contacting said swash plate, a spring urging said contacting means toward said swash plate and means for drivin said pulleys at relative speeds ior cation 0! said spindle.

8. A-machine tool including, in combination, a'

rotatable spindle, a driving pulley secured to said eilecting the rotation and reciproplate and means for driving said pulleys at rela tive speeds for eiiecting the rotation and reciprocation oi said-spindle, a grinding head carried by said spindle, and means for controlling the feeding of a work piece relative to said grinding head !or limiting its degree of movement.

9. A grinding machine including, in combination, an abrading head, a spindle for rotating and reciprocating said head, means for expandcontrol lever for stopping the rotation oi the spindle and for'collapsing said head when'moved in one direction and for expanding said head and starting the rotation of the spindle when moved in an opposite direction.

10. A; grinding machine including, in combination, a base, a rotatable spindle, means ior rotating and reciprocating said spindle, an

abrading head carried by said spindle. means for expanding and contracting said abrading head, a clutch in said driving means, a brake .ior said spindle, and control means for contracting said head, for disconnecting said clutch and applying said brake to said spindle.

11.'A grinding machine, including, in combination, a base, a spindle rotatable thereon and mounted for axial movement, an abrading element on said spindle, a pulley having a swash plate disposed on one face and having its axis aligned with that of said spindle, a pulley on said spindle, a projection on said shaft pulley engaging said swash plate, and a spring for urging said spindle towards said swash plate.

12. A machine tool including, in combination,

-a rotatable element mounted for axial move,-

ment, a pulley in driving relation to' said element, an additional pulley mounted adiacent to said first pulley and rotatable independently thereof, a swash plate, connection between said swash plate and one of said pulleys, means providing connection between said swash plate and said rotatable element such that the element is moved in reciprocation following the slope oi the swash plate, means tor driving said pulleys at relative speeds 'ior eilecting rotation and reciprocation oi said rotatable element. an abrading-element actuated by said rotatable element in rotation and reciprocation, and means ior adlusting the slope of said swash length of the movement of saidelement in reciprocation.

WILLIAM H. HARRIS, Ja.

plate to vary the

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