US2195055A - Honing tool - Google Patents

Description

Mai-ch 26, 1940.

D. A. WALLACE HONING TOOL Filed Aug. 21. 193'! 3 Sheets-Sheet 1 M 3% mm mm I INVENTOR n 4144 fl l4 dZldze.

March 26, 1940. D. A. WALLACE 2,195,055

*aoume TOOL Filed Aug. 21, 1937 3 Sheets-Sheet 2 2 as I INVENTOR TORNE Ya March 25,1940. WALLACE 2,195,055

HONING TOOL Filed Aug. 21, 1937 3 Shuts-Sheet 3 INVENTOR W WWKZQQ TORNEYS.

Patented Mar. 26, 1940 UNITED STATES,

PATENT orrlca HONING TOOL David A. Wallace, Detroit, Mich assignor to Chrysler Corporation, Highland Park, Miclu, a corporation of Delaware Application August 21, 1937, Serial No. 160,198

19 Claims. (Cl. 51-218) creased, either progressively or in steps a pre- My invention re tes to honing tools and particularly a simplified tool wherein the radial movement of a single abrading element positively effects the engagement of 'a plurality of elements with the wall of the cylinder to be machined.

It has been the practice heretofore to expand a plurality of abrading elements radially of the axis -of the tool by cones or similar elements which produce a sliding engagement on an inclined plane through mechanical adjusting elements. When wear occurred on 'one' stone a greater amount than on the other, due to the softer bond and abrading material, such stone became 15 inefiective to cooperate in producing the machining operation and an unbalanced condition occurred to the abrading head.

In practicing my presentinventioml employ at least three abrading elements, two of which are 3 relatively fixed to the body of the abrading head, while a third is radially movable to cause all of the abrading elements to contact with thecylinder wall. In the case. of employing two fixed stones and moving a third stone, contact will be obtained between all of the stones and the cylinder wall, irrespective of the irregular wear of the various stones. A universally jointed driving driving head is utilized to permit the axis.of the abrading head to shift relative to the axis of the 30 cylinder being honed so that positive contact with the surface being machined will be had at all times by all three of the abrading elements. If one of the stones should wear, faster than the other, constant pressure between all ofthe stones and the surface to be machined will be maintained through the shifting of the axis of the tool under the force of 'the movable abrading element. As a result of this unique construction, constant pressure is at all times maintained on all of the 40 abrading elements when engaged with the surface of the cylinder being machined.

The stones which are fixed against radial movement may be 50 mounted as to be shiftable axially preferably disproportionate amounts at 4 each half cycle of reciprocation. The stones will be stationary at the end of the stroke and will be progressively moved to have all the surfaces of the three stones changed relative to each other to thereby control the grain relation presented to .30 the work during each half cycle of reciprocation.

The fluid employed to control the position of thestones is preferably introduced to the actuating element in a large volume at low pressure. This immediately moves the abrading elements 55 into contact with the cylinder wall, which contact is initially light. The stones under lightpressure are more effective to rough out the imperfections on the cylinder wall without harming the stones. As the honing progresses, the pzes- (it) sure for urging the stones against the work is indetermined amount, or until the operation is completed.

Accordingly, the main objects of my invention are: to provide an abrading head having at least two fixed abrading elements and an additional element which is movable radially of theaxis of the head; to provide positive driving means for moving one of a plurality of abrading elements radially of the axis of the tool; to provide hydraulic .means for positively adjusting one of a plurality of abrading elements radially of the axis of the tool; to provide an adjustable stop for limiting the movement of the hydraulically operated device for radially adjusting an abrading element; to drive a tool through a universal' connection to permit the axis of the toolto assume any position relative to the axis of. the

cylinder to be machined; to employ a cam operated by hydraulic means for positively controlling the expansionof an abrading element during a honing operation to initially utilize a minimum pressure for'urging the stones into contact with the cylinder wall, which pressure is increased as the honing operation progresses; and, in general, to provide an abrading tool for machining cylindrical elements which is simple in construction, positive in operation, and economical of; manufacture.

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

Figure l is a view, partly in section and partly in elevation, of a honing tool embodying features of my invention:

Fig. 2 is a side view, partly in section and partly in elevation, of the honing tool illustrated in Fig. 1;

Fig. 3 is an end view of the structure illustrated in Fig. 2, as viewed from the line 3-3 thereof;

- .Fig. 4 is a sectional view of the structure il- I lustrated in Fig. 5, taken on the line 6--6 thereof;

Fig. '7 is a sectional view of the structure illustrated in Fig. 6, taken on the line 1-1 thereof;

Fig. 8 is an end view of the structure illustrated in Fig. 5, asviewed from line 8-8 thereof;

Fig. 9 is a broken view of the structure illustrated in Figs. 5 to 8 inclusive:

Fig. 10 is a sectional view of a control head for the tools herein illustrated, showing a further form thereof Fig. 11 is an enlarged sectional view of the structure illustrated in Fig. 10, taken on the line II-II thereofi Fig. 12 is an enlarged sectional view of the structure illustrated in Fig. 10, taken on the line I2-|2 thereof with the ratchet and pawl in en-' gaged position; and

Fig. 13 is a view of structure; similar to that illustrated in Fig. 12, with the ratchet and pawl in released position.

My invention comprises, in general, a tool having a body portion supporting a plurality of abrading elements, at least one of said elements being movable radially while opposite elements are fixed against radial adjustment.

In Figs. 1 to 4, I have illustrated one form of tool wherein a body II has a pair of abrading elements I2 and I3 fixed thereto by a suitable clamping element I4 securedto the body by screws I5. A lateral slot I6 is provided in the central part of the body having a plurality of transversely disposed circular openings, I1 communicating therewith. Cylindrical elements I8 are disposed in the openings and secured in eccentric relation to a shaft I9 which has a pinion 2| machined or otherwise provided thereon. A

radially adjustable carriage 22 is disposed in the slot I6 for movement radially of the body of the tool, having an abrading element 23 mounted thereon in any suitable manner, herein illustrated as by clamps 24. An axially reciprocating piston 25 is journaled within the carriage 22 having rack teeth 26 on one face thereof.

After the carriage is disposed in the slot I6. the plurality of shafts I 9' are mounted therein with the gears 2| in mesh with the teeth 26 of the rack provided on the piston 25. Thereafter the eccentric elements I8 are secured to the ends of the shaft and suitable sealing washers 21 may be disposedin the opening in the body. A passage 28 is provided lengthwise of the carriage which communicates with the lower end of the cylinder 29 in which the piston 25 operates. The opposite end of the carriage is provided with a passage 3| communicating with the opposite end of the cylinder 29. The passages 3| and 28 are joined by two flexible conductors 32 and 33, respectively, to passages in the body to permit the movement of the carriage while delivering fluid under pressure thereto. Suitable packing washers 34 are provided at each end of the piston 25 to provide a seal for the fluid introduced into the cylinder 29 at either end of the carriage. An

adjustable element 35 limits the degree of axial movement of the piston and therefore the expansion of the abrading element 23 to limit the size of the cylinder to be machined by the tool.

The body II of the tool has a collar 36 secured thereto which is rotatable relative to the body and employed as a means for delivering the fluid under pressure to the carriage 22. Suitable fluid delivering rings 31 are mounted on the shank of the tool within the collar 36, having rooves 38 therein to permit the flow of fluid thereabout and through apertures 39 into apertures 4| and Y42 within the body. The apertures 4| and 42 communicate through connectors 48 with flexible conductors 32 and 33, respectively, hereinabove described.

Fluid is delivered through conductors 43 and 44 and apertures 45 and 46 in the collar 36, into the recesses 38 provided in the oil delivering rings 31. The collar 36 is also provided with a stud 41 which abuts against a stop element (not shown) to prevent the rotation of the collar while permitting the reciprocation and rotation of the tool. Suitable packing glands 48 are disposed between the rings 31 beneath the collar for sealing the rings relative to the tool shank and collar 36.

The rings and packinggland are retained in clamped relation by a threaded collar 43, mounted within the collar 36. The collar 36 is retained on the end of the shank of the tool by a suitable clamping ring 5| through which the end 52 of the tool extends and forms a projection to be received by a bayonet type of socket which engages a pin 53 for locking the tool thereto.

The socket, preferably, is provided with the universal joint to permit the axial shifting of the tool relative to the driving element to permit the tool to center itself withina cylinder to be honed. This is necessary in view of the fact that the one stone orabrading element 23 is movable while the abrading elements I3 and I2 are retained in fixed relation to the tool axis. When the abrading element 23 is moved outwardly, the axis of the tool shifts relative to the axis of the work and the universal driving connection is therefore a desirable feature. I t is to be understood, however, that the work could be mounted to shift relative to the tool so that the tool could be retained in fixed relation relative to the driving head so that the work could align itself relative to the axis of the tool as the axis changes.

In operation, when fluid is introduced into the conductor 43 it will flow through the passages 4| and 28 into the lower end of the cylinder 29 to impinge upon the piston packing 34 on the end of the piston -25 and cause the piston to move upwardly in the tool. as viewed in the figures. The upward movement of the piston rotates the gears 2| and therefore the cam elements I8 to cause the abrading element 23 to move outwardly and force the abrading elements I3 and I2 along therewith into engagement with thesides of the cylinder being honed. The feeding of the element 23 will continue during the honing operation through the continued upward movement of the piston 25 until the upper end thereof engages the end of the stop element 35, after which no more radial feeding of the element 23 can occur.

After the honing operation has been completed. fluid is introduced intothe conductor 44 and the conductor 43 operates as a return conduit for the fluid in the lower part of the cylinder 29. The fluid under pressure now flows through the passages 46 and 42 to impinge upon the upper piston packing 34 to move the piston 25 downwardly to rotate the gears 2| and cams I8 to their original position. which is that in which the abrading element 23 is retracted.

In Figs. 5 to 9, I have shown a further form which my invention may assume, that wherein a v cylinder 55 encompasses a piston 56 secured to body 58 and has adjustably secured thereto a cam.

block 6| containing a pair of cam surfaces 62 and 63. The cam block 6| is retained by a pair of pins 64 in fixed relation to the carriage 58, the elements being adjustable longitudinally of each other by a plurality of apertures 65 which selectively receive the pins 64. Through the shifting of the pins in the apertures 65, the surfaces 62 and 63 are positioned axially of the body relative to the piston 51 so that the backing element 61 for *the abrading stone 68 is shifted to provide a greater or lesser diameter to the honing tool. The backing element 61 is provided with a pair of sloping surfaces 69 and 1| which mate -with the cam block BI.

screws 18.

the sloping surfaces 62 and 93, respectively, of The piston 58 is moved down-. wardly-through the introduction of fluid through the aperture 12 in the driving head portion 13 to thereby move the cam block 6| dial movement of the backing element 61 against the bias of a pair of springs 1.4 retained by suitable clips 15 to the tool body. The abrading element 68 is secured to a metal sheath 16 by friction or by a suitable adhesive material such as resin, glue, lead, and the like. The sheath is provided with projecting ends 11 which are secured to the backing element 61 by suitable An adjustablescrew of the tool in the line of movement of the carriage 59 to bar further axial movement of the carriage at a predetermined point-and thereby to limit the diameter ofthe hole which will be finished by the tool. It is to be understood that the screw 19 may be adjusted from time to time as the surface of the abrading stone 88 becomes worn. a

The driving head 13 is fastened to the body-58 by suitable screws 8| and sealed thereto by a suitable gasket 82. A relatively rotatable collar 83 is mounted on the driving head 13 and is provided with rings and packing elements similar to those described hereinabove with relation to the structures illustrated in Figs. 1 and 2, for

delivering fluid to either side of the piston. The

conductor 84 delivers fluid to the top side ofthe piston while the conductor 85 provides a return passage when the abrading operation is to be performed, and the conductor 85 introduces fluid to the lower end of the piston while the conductor 84 functions asa return passage when the abrading stone 68 is retracted. The collar is retained on the body by a thrust ring 86 which is secured .to the head by a pin 8'1.

The side of the body 58 opposite to that in which the abrading stone 98 is disposed, has a pair of abrading stones 89 and 9| fixed against radial movement while permitting a slight axial movement relative to the body. Dovetail carriers 92 are mounted within the body and having the abrading stones 89 and 9| secured thereto by screws 18 passing through the sheath ends 11. Stop elements 99 and 94 are provided in the bottom of the slots containing the dovetail carriers 92, while suitable stop elements 95 and 95 are provided at the top thereof. In the figure, the abrading elements are disposed againstthe top stop elements, and it will be noted that the space 9'! between the carrier 92 and stop element 93 is greater than the space 98 disposed between the.

carrier 92 and the element '94. It is evident that during each change in direction of reciprocation of the tool, the abrading stones 9| and 92 will shift lengthwise slightly relative to the tool body disproportionate amounts and will change the grain relation of the stones in a radial plane.

It is understood by those skilled in the art that the grain surface of the stone produces minute scratch marks on the surface being abraded; the softer stone having a fine grain \structure operated under proper pressure will produce finer marks and a highly polished fin.- ish. These marks may vary because of the variation in grain structureof the stones and the overlapping of certain of the grains may cause a greater number and deeper marks on the surface to be finished. By shifting all of the three stories relative to each other at each half cycle of reciprocation of the tool, such a condition is' to effect the ramovement of the axis of the tool to shift relative to the body and,

19 is provided at the end the tool is mounted in work is permitted to shift relative to the axis of abrading stone movement or rotation stant, depending upon broken up and difl ent grain structure will be presented in a radial plane by the various stones.

In operation, the tool is disposed within the work and fluid is introduced through the conductor 84 to cause the piston 56 and expansion of the carriage 59 to thereby eflect abrading stone 68 will cause the as the stone engages the wall to be machined, the tool will shift bodily in the opposite direction to bring the stones 89 and 9! into contact with the. wall after which a predetermined pressure will be provided between the three stones and the wall. The driving head' of the tool is provided with a universal joint to permit such shiftin or a machine in which the the tool. The expansive movement of the stone 68 will continue until the carriage 59 strikes the stop 19. After the honing operation is completed, the fluid circuit is changed to ,have the fluid introduced through the conductor and returned through the conductor 84 to return the piston and permit the spring 14} to retrieve the 59. It is to be understood that during the honing operation the driving head for the tool reciprocates the tool and provides a thereto. At each half cycle of movement the stones 89 and 9! will shift longitudinally different amounts and assume new positions relative to the abrading stone 68 which is retained against suchlongitudinal movement. As a result, the relative position of all of the stone faces which contact the cylinder wall shift relative to each other to produce a finer and more uniform abrading operation.

Referring to Figs. 10, 11, 12 and 13, I have illustrated a further novel construction which may be employed with any of the tools herein illustrated, or. any other type of honing. tool wherein abrading, elements are expanded under pressure. The cylinder wall to be machined is rough and will vary in diameter due to certain surface defects. operate the honing tool with the abrading elements expanded under a minimum pressure to produce honing'in the-nature of a roughing operation to clear up the defects before material pressure is applied to the stones. This prevents the rapid break-down of the stones and produces more uniform abrading when effecting a finishing operation. Accordingly, the fluid'admitted to the piston is so controlled as to initially provide a large volume to immediately actuate the piston to produce expansion and at the same time to have the pressure at a minimum. As the tool operates, a valveor other means is actuated through the rotation, reciprocation or ycombined movement, of the tool or otherwise, to

increase the pressure on the piston as the machine operation progresses. The increase of pressure may be produced in a uniform or nonuniform rate which may be intermittent or conthe means employed to control the flow of fluid. that the increase inpressure may occur from the initial movement of the abrading elements intocontact with the cylinder wall through only a small portion of the cycle of operation or may extend over a greater portion of or the entire cycle of machining, or such increase iii-pressure may occur sometime. after the operation is started. I -t The'mechanism for controlling the pressure 75 I the downward movement of abrading stone 68. The radial It was found advantageous to initially- It is to be understood is shown more, for the purpose of illustration rather than by way of limitation as it will be understood by those skilled in the art that other structures could be devised for producing the novel control of the pressure. The body 58 of the tool is similar to that illustrated and de--.

scribed with regard to the structure illustrated in Figure 6. The driving element IOI, therefore, is provided with an aperture I02 through which a fluid is conducted to the top side of the piston 56 to effect expansion of the abrading element 68. A passageway I03 is also provided in the driving element IOI communicating with a conductor ring I04 which is connected through a valve seat I05 to a discharge conduit I06. A valve I0! is threaded at I08 in the collar l09 which is similar to the collar 83 shown in Fig. 6, except for additional length to encompass conductor ring I04. The valve is secured to a ratchet wheel III adjacent to the supporting brackets II 2 between which a spring H3 is mounted, having one end fixed to the bracket while the other end is secured in a slot I I4 in the valve shank. A ratchet lever II 5 is pivoted on the bracket II6 by a pin II'I about which a spring I I8 is disposed for urging the lever H5 in a clockwise direction to have the actuating end II9 thereof engage the teeth I2I of the ratchet wheel III. The opposite end I22 of the lever projects outwardly between lugs I23 and I24 provided on the side or other fixed portion of the machine. The lugs may be mounted in dovetail slides to be adjusted from time to time as the stroke of the honing tool is changed in accordance with the lengths of the different work pieces operated on. An additional bracket I25 isprovided on the sleeve I09, the end of which pivotally supports a pawl I26 which is biased by a spring I21 to have the end I28 thereof engage teeth I2I oi the ratchet wheel III. A link I29 is pivoted to the pawl I26 and connected to a slot I8I in the end of the lever II5.

the abrading operation the tool is withdrawn from the work at which time the end I22 of the lever II5 will engage lug I 20 and move the end II9 of the lever and the end I28 01 the pawl I26 out of engagement with the teeth I2I oi the ratchet wheel III, which is the position illustrated in Fig. 13. As soon as the ends are re leased from the teeth, the bias of the spring II3 will operate to turn the valve I01, which operating in the thread I00 will move from the seat I05 and open the passageway to the conduit I08.

Upon inserting the tool within the cylinder to be machined, the introduction of the fluid through the passageway I 02 will immediately provide a suflicient volume of oil to operate the piston 56 to effect the contact of the abrading element with the cylinder wall. The fluid, however, is free to flow from the cylinder through the passageway I03 and valve I01 through the outlet conduit I06. in this manner, a large volume of fluid under minimum pressure is provided for the initial operation of the abrading eleof the fluid illustrated in Figs. 10, 11, 12 and, 13 ment into contact with the cylinder wall. At

the end of each cycle of reciprocation as the tool operates, the end I22 of the lever II5 will engage the lug I24 to cause the end IIO of the lever to engage a tooth of. the ratchet wheel III and to advance the ratchet wheel in rotation a predetermined amount. Such advancement of the ratchet wheel will continue at each cycle of reciprocation until the end IIO of the lever passes over a portion I33 on the peripheral edge of the ratchet wheel upon which no teeth are provided. The continued operation of the tool in reciprocation will thereafter have no effect in advancing the ratchet wheel or to change the position of the valve I0'I relative to its seat. I05.

The amount of rotation of the ratchet wheel and valve may be controlled through the change of position of the portion I33 relative to the valve stem and also through a change in position of a stop I34 relative to an adjustable lug I35 as illustrated in Fig, 13 which provides further control of the amount of change in pressure produced during the tool operation. The extent in time of the change in thepressure with relation to .the entire time of the machining operation may be adjusted through the size of the teeth I2I, the amount of tilting to the lever II5, change in size ofthe ratchet wheel, and through other changes well known to one skilled in the trated in Figs. 10 to 13 inclusive, the immediate expansion of the abrading elements into contact with the cylinder wall is effected upon the delivery of the fluid to the cylinder, which contact will be produced under a minimum pressure irrespective of the pressure of the fluid being delivered. The fluid will pass from the cylinder through the control valve which will begin to close the passage as the honing operation progresses to thereby increase the pressure in the cylinder and to provide greater pressure to the abrading elements. This pressure will continue to increase as the operation progresses until a predetermined amount of pressure is reached, after which the operation may be discontinued or maintained under a fixed pressure until the machining operation is completed.

While I have described and illustrated several embodiments of my invention, it will be apparent to those skilled in the art that various changes, omissions, additions and substitutions 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:v

1. A honing tool having a body portion with adjacent abrading elements thereon fixed against radial movement, a carriage in said body portion oppositely disposed to said elements, an abrading element on said carriage, and means for adjusting said carriage and abrading element radially to force said three abrading elements into contact with the wall of a cylinder to be machined.

2. A honing tool having a body portion on which a plurality of abrading elements are fixed against radial movement, a radially adjustable carriage on said body portion diametrically disposed relative to a medial point between said elements, an abrading element on said carriage, a longitudinally movable element in said tool for effecting the radial movement of said carriage to cause all of said elements to contact the wall of a cylinder under pressure through the shifting of the body of the tool, and fluid means for actuating said longitudinally movable means.

- 3. A honing tool having a body portion on which a plurality of abrading elements are fixed against radial movement, a radially adjustable carriage on said body portion, an abrading ele-. ment on said carriage, a longitudinally movable element in said tool for effecting the radial movement of said carriage, fluid means for actuating block on said carriage adjustably secured there- 11.'In a honing tool having abrading elements, means for moving the abradingelements into em to for movement therewith while engaging said radially adjustable abrading element.

5. In a honing tool, a body portion having a plurality of abradingelements fixed against radial movement, a radially adjustable abrading element disposed in said body portion, an axially movable carriage in said body portion, a cam block on said carriage adjustable longitudinally thereof for movement therewith while engaging said radially adjustable abrading element, a cylinder in said body portion, and a piston in said cylinder connected to said carriage.

' 6. In a honing tool, a body portion having a plurality of abrading elements fixed against radial movement, a radially adjustable abrading element disposed in said body portion, an axially movable carriage insaid body portion, a cam block on said carriage adjustable longitudinally thereof for movement therewith while engaging said radially adjustable abrading element, a cylinder in said body portion, a piston in said cylinder connected to said carriage, a collar on said body portion rotatable relatively thereto,

and means for delivering a fluid through said col- ,lar to said cylinder.

abrading elements thereon supported against radial movement, means for so mounting said elements in said body portion as to permit a single longitudinal shifting of said stones therein, and an abrading element mounted in said body portion adjustable radially thereof...

8. In a honing tool, a'plurality of'abrading elements, means for mounting said abrading elements in said honing oi to permit a slight relative axial shifting thereof disproportionate amounts at each change of direction in the reciprocation of the tool.

9. In a honing tool, a body portion having a plurality 'of abrading elements secured thereto, atleast one of said abrading elements being adjustable radially, the other said abrading. elements being so mounted as to shift sli htly relative to each other longitudinally of the tool.

10. In a honin plurality of abrading one of said abrading elements secured thereto, elements being adjustable radially while secured against longitudinal movement, others of said abrading elements being secured against radial adjustment while being mounted to shift slightly disproportionate amounts longitudinally of the tool.

gagement with the wall of the to be machined with a predetermined pressure.

tool, a body portion having a and means including a valve on'said tool for increasing the pressure thereafter.

12. In a honing tool having abrading elements, Y

means for moving the -abrading elements into engagement with the wall of the cylinder to be machined, meansfor introducing a volume of fluid under low pressure to said moving means to produce a rapid initial movement of the abrading elements into contact with said wall and to initially machine under low pressure, and means for thereafter increasing the pressure between said elements and wall.

13. m a honing tool having abrading elements,

means for moving the abrading elements into engagement with the wall of the cylinder to be machined, means for introducing a volume of fluid under low pressure to said moving means to produce a rapid initial movement of the abrading elements into contact with said wall and to initially machine under low pressure during the roughing operation, andmeans for thereafter progressively increasing the pressure between I. the abrading elements and said wall.

14. In a honing tool having abrading elements, means for moving the abrading elements into engagement with the wall of the cylinder to be machined, means for introducing a volume of fluid under low pressure to said moving means to produce a rapid initial movement of the abrading elements into contact with said wall and to initially machine under low pressure, and means for thereafter progressively increasing by stepsthe pressure between the abrading elements and said wall. g

15. The method of abrading which includes the steps of, initially abrading with a light pressur thereafter abrading with a greater pressure, and

finishing with a third pressure.

16. In an abrading device, an abrading element, means for advancing said element into contact with a surface to be machined, means for initially applying a low pressure between said element and surface, means for thereafter applying a higher pressure between said element and surface, and means for controlling the of operation under said low pressure.

17. The method of abrading which includes the steps of moving an abrading element inte contact with and upon a surface to be machined, maintaining pressures between said element and said surface proportionate to their area of'contact as the character of said surface changes during operation thereon.

18. The method of lapping a piece of work which comprises applying with a predetermined force a lapping element to a surface of a piece duration of work to establish a. predetermined unit lapping pressure during one stage of lapping of said surface, and increasing said force thereafter as the area of contact between said surface and said lapping element is increased by the removal of irregularities-from said surface.

19. The method of which comprises applying with a predetermined force alarming element to a surface of a piece of work to establish a predetermined unit lapping pressure during initial lapping of said surface, producing relative lapping movements between said lapping element and said surface, and intermittently increasing said force to a higher .predetermined value without decreasing said force between each of a selected number of said lapping movements.

. DAVID A. WALLACE.

lapping a piece of work I

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