US2779139A - Lapping machine - Google Patents

Description

Jan. 29, 1957 Filed Nov. 24, 1952 5. A. BOETTCHER ET AL LAPPING MACHINE 2 Sheets-Sheet l INVENTORS.

STE HENAIBOETTCHER BY HAROLD w. GOULD Jan. 29, 1957 Filed Nov. 24, 1952 s. A. BOETTCHER ET AL 2,779,139

LAPPING MACHINE 2 Sheets-Sheet 2 A INVENTORS:

W STEPHEN ABOETTCHER a. X HAROLD w. GOULD BY fdwawd R, 52mm.)

United States Patent LAPPING MACHINE Stephen A. Boettcher and HaroldW; Gould, Evanston, Ill., assignors to Crane Packing ,Company, Chicago, Ill., a corporation of Illinois Application November 24, 1952,- Serial No. 322,182 1 12 Claims. (Cl. '51-13"1) The present invention relates to alapping machine.

fixture or work holder designed for -use:-in connection August 28, 1951, for Lapping-Ma'chine.

without modification, be employed in connection with other types of lapping machines-having associated there with a lap surface which is movable in its own plane to Y produce the necessary lapping operations;

This invention is designed as an improvement over'the lapping machine fixture shown and described in the copending application of Stephen A. Boettche r, Serial No.- 282,96( filed April 18, 1952', for a Method of'and-App'aratus for Lapping Articles, now PatentNo. 2,722,089 dated November. 1, 1955. In this application-just referred to, there has been shown and described a method of and apparatus for producing fiat surfaces on'articles by a lapping operation wherein the plane of the finishedlapped face on the article assumes a definite and predetermined angularity within very fine limits with respect to the plane of some other face on the article or to a fixed reference plane established relative to the-article itself. According to the method and apparatus employed in this application, there is provided an article holder or fixture to which an article such as a thin piezoelectric crystal may be fixedly secured and by means of which it may be applied to the lap surface for lapping purposes with the weight of the fixture resting upon the article to maintain the latter in contact with the lap surface. During lapping, the article holder is moved toward the lapped surface at a rate commensurate with the speed of lapping. The article holder is provided with a fixed non-wearing three point suspension for the holder on the lap surface in such a manner that continued lapping of the face of the article will bring the individual points of suspension into coincidence with the plane of the lap surface. Since the three points of suspension are of a non-wearing nature, movement of the suspension points into such coincidence with the plane of the lap surface will relieve the pressure of the article on the lap surface and substantially terminate further lapping operations. The improved fiXture comprising the present invention embodies the same general principles. as the fixture shown in the application of Boettcher but it constitutes 'an improvement thereover in that novel means are provided for efiecting initial adjustment of the suspension points relative to the body of the fixture with the adjustment being carried out within very fine limits so that the fixed reference plane which forms a basis for the lapping operations may be accurately established prior to the commencement of lapping operations.

It is, therefore, among the principal objects of the present invention to provide a lapping fixture or article holder of the type shown in the application of Boettcher, to-

gether with novel means for adjusting the positions'of the suspension points associated with the fixture in such 1.

2,779,139 Patented Jan. 29, 1957 2 I a manner that an extremely fine adjustment involving very small displacements of the suspension points is attained.

Astill further object of the inventionis to provide a fixture of this character in which the adjustment of the individual suspension points may be made by rotation of adjustment screw and in whicha fairly large increment of turning movement of the adjustment screw will result in an extremely small component of linear displacement in a desired verticaldirection of-the individual suspension point.

In carrying out this last mentioned object, the invention contemplates the provision of a pivoted or swingable support for the suspension point together with means for adjustably tilting or swinging the support about an axis. The suspension point is mounted on the tiltable support at a region remotefrom its tilting axis so that when the support is tilted about its axis the suspension point will be" moved in 'an arcuate path having both horizontal and vertical components of motion. The horizontal component of motion through which the suspension point moves is a function of the sine of the angle of tilting of the support and, although its absolute movement is small, its differential. rate of increase is comparatively large. Thevertical component of movement of the suspension point is a function of the cosine of the angle of tilting movement of the support and its difierential rate of increase is therefore extremely small. Tilting movement ot the support is efiected by an adjustment screw of relatively fine pitch so that each turn of the screw will effect but a small angular displacement of the support. This small angular displacement results in a correspondingly small component of lateral displacement of the suspension point and a much smaller vertical component of displacement; of the point. Thus the rate of displacement of the suspension point in its effective vertical direction is an extremely small differential of the rate of turning movement of the adjustment screw. In this manner an angular displacement of the adjustment screw well within the capability and cognizance of an operator will result in an almost infinitessimal displacement of the suspension point relative to the fixture as a whole.

Still another object of the invention is to provide an adjusting means of the character briefly outlined above in which the adjustment is a positive One and which will permit of no lost motion between the movable parts involved so that an adjustment may be made in either direction without involving errors due either to slack or other lost motion between the parts.

Still another object of the invention'is to provide an adjusting mechanism for suspension points in a fixture of this character which, once the adjustment has been made, will remain permanent so that there is no shifting of the parts tending to destroy the adjustment.

The provision of a fixture of this character which has associated therewith means for providing accurate adjustment of its suspension points within very fine limits, yet in which the adjusting means is not delicate and which on the contrary is rugged and durable and therefore is unlikely to get out of adjustment; one which may withstand sudden shocks without affecting the adjustment; one which is possessed of a minimum number of moving parts and which therefore is unlikely to get out of order; one which may be manufactured at a low cost by simple machining operations, and one which otherwise is well adapted to perform the services required of it are further desirable'features that have been borne in mind in the production and development of the present invention.

In the accompanying two sheets of drawings forming part of this"- specification, several embodiments of this invention have beenportrayed purely for illustrated purposes; In these drawings:

Fig. 1 is a top plan view of the fixture constructed in accordance with the principles of the present invention and showing the same operatively applied to the rotary lap surface of the lapping machine.

Fig. 2 is a sectional view taken substantially along the line 2--2 of Fig. 1.

Fig. 3 is a perspective view of the fixture or article holder shown in Fig. 1.

Fig. 4 is a perspective view similar to Fig. 1 showing another form of fixture specifically designed for use in connection with the lapping of articles having angular surfaces such as optical prisms or the like.

Fig. 5 is a sectional view taken substantially along the plane indicated by the line 5-5 of Fig. 4.

Fig. 6 is a sectional view similar to Fig. 5 showing a modified form of adjusting means for the fixture suspension points.

Fig. 7 is a diagrammatic view illustrating certain trigonometric functions involved in connection with the suspension point adjusting means of any of the fixtures shown in Figs. 1 to 5 inclusive.

Fig. 8 is a diagrammatic view similar to Fig. 7 illustrating the trigonometric functions involved in connection with the adjusting means of Fig. 6.

Fig. 9 is a detail fragmentary view showing a slightly modified form of adjusting means for the fixture suspension points.

In all of the above described views similar characters of reference are employed to designate similar parts throughout.

In compliance with section 4888 of the Revised Statutes, several preferred forms of the invention have been shown in the drawings and will be described herein, but it should be understood that the invention is not limited to the specific disclosure made, and that the appended claims should be construed as broadly as the prior art will permit.

Referring now to the drawings in detail, Figs. 1 to 3 inclusive illustrate an improved article holder or fixture 10 suitable for use in the lapping of relatively thin articles such as piezoelectric crystals so that the opposite surfaces of the crystals may be brought to a high degree of flatness and. parallelism. In Figs. 4 to 6 inclusive a modified form of fixture 12 suitable for use in lapping an angular face on the surface of a relative large article, as for example an optical prism, has been illustrated.

The fixtures 10 and 12 are both suitable for use in connection with various forms of lapping machines and particularly the form of lapping machine shown and de scribed in the above mentioned patent to E. I. Bullard, No. 2,565,590. Such a lapping machine has been fragmentarily illustrated in Figs. 1 and 2 and only those portions of the machine necessary to illustrate the particular use to which the present fixture is put have been shown.

The particular lapping machine selected for illustration includes a circular lap plate 14 having an upper substantially flat annular lap surface 16. The lap plate 14 is mounted for rotation about a vertical axis so that the plane of the lap surface is substantially horizontal. Any suitable means (not shown) may be employed for continuously rotating the plate 14 about its vertical axis at a constant rate of movement.

The surface 16 of the lap plate 14 is adapted to be continuously dressed and maintained in its original flat condition by means of a conditioning ring 18, the external diameter of which is greater than the radial dimension of the lap surface so that the ring may overhang either the inner or the outer edge of these surfaces. Such overhanging of the conditioning ring prevents the formation of shoulders or grooves in the lap surface which would render it unfit for the production of flat faces on the articles undergoing lapping. The ring 18 is preferably formed of close-grained cast iron such as Meehanite, and has a cross section such as shown in Fig. 2. The ring 18 is held against circumferential shifting movement on the lap plate 14 but is free to rotate about its own vertical axis. One means for thus restricting the movement of the ring 18 is fully disclosed in the above mentioned Bullard patent and another means is shown in the patent to Roshong, No. 2,627,144, dated Februray 3, 1953, for Lapping Machine. It is deemed sufficient to state for illustrative purposes herein that the ring 18 is capable of rotation about its fixed vertical axis under the influence of frictional contact with the surface 16 of the lap plate 14. The lap surface 16 is adapted to have applied thereto a suitable lapping compound in the form of an oil grit which is used to assist in grinding or lapping the articles positioned on the lap surface. The means for applying and distributing such a lapping compound over the surface of the lapping plate has not been disclosed herein and reference may be had to the above mentioned Bullard patent for a disclosure of such a means.

The improved article holder or fixture, as it is more generally termed, shown in Figs. 1 to 3 inclusive, is adapted to be loosely positioned within the conditioning ring 18 and this fixture involves in its general organization a generally triangular block 22 which may be formed of steel and it is provided with three inwardly bowed or curved sides 23 which, in efiect, establish three radially extending diverging arms 24. The apices of the triangular block 22 are of appreciable extent and are convex in configuration. The curvature thereof being substantially equal to the curvature of the inner periphery of the conditioning ring 18. The block 22 is provided with a substantially flat underneath surface 26 (Fig. 2) to which the articles undergoing lapping may be secured. For illustrative purposes a series of articles A in the form of quartz crystals having extensive generally planar surfaces to begin with are shown as being wrung to the surface 26 by means of the application of the small amount of moisture which is placed on the contacting surfaces prior to application of the articles to the surface 26. When the article is then applied to the underneath surface of the block 22, its face makes intimate contact with the surface 26 so that the article is firmly held to the fixture by phenomena which are believed to be a combination of molecular adhesion and atmospheric pressure.

The block 22 is provided with three spaced vertically extending bores 28, each bore being provided in the block adjacent an apex of the generally triangular structure. Actually the bores 23 are in the form of split clamping bores, there being a vertical split 34) provided at each apex communicating with the adjacent bore 28. Each split 30 provides a pair of opposed clamping arms 32 on opposite sides of the split and each pair of arms is adapted to be drawn together to vary the size of the bore 28 by means of a pair of clamping screws 34 having enlarged heads 36 seated in recesses 38 provided in one clamping arm 32 and having shanks threadedly received in the other clamping arm.

Each bore 255 has disposed therein a cylindrical supporting rod 40, the vertical position, of which, within the bore, may be adjusted by loosening the clamping screws 34 to permit manual placement of the supporting rods 40, after which the clamping screws may again be tightened. The lower end of each supporting rod 40 is provided with a socket 42 therein designed to facilitate mounting of a suspension element in the form of a diamond rest 44 having a frusto-spherical surface 46 providing a suspension point for the fixture 10 as a whole, such suspension point being for a purpose that will be described presently. The diamond rest 44 may be in the form of a commercial diamond, the surface of which is rounded, with the diamond being brazed in fixed position within the socket 42.

The three diamond rests 44 have a hardness which is greater than the surface of the lap plate 14 or than the hardness of the floating abrasive particles on the lap plate so that when these rests are in contact with the arm-1 s surface of the lap plateqthewear on' thediamond tests or upon the lap plate itself will be negligible. These suspension points 46 are employed in connection with the fixture l inasmuch as three rests will, when bearing against the lap surface 16, determine orestablish a plane for the underneath article-supporting surface 26.

An article such as a crystal A, when wrung to the supporting surface 26 and lapped by this surface to completion, as determined by movement of the diamond rests 44 into coincidence with the plane of the lap surface, will be found to have a lapped .face parallel to the surface 26. It will be appreciated that for best results, the surface 26 of the block 22 must itself be planar. Otherwise its deviation from a plane vmay be transmitted to the face of an article being lapped. It must be assumed therefore that the surface 26 is preferably fiat and smooth and it must also be assumed that the articles are preferably wrung onto this surface without the inclusion of any g-rit or viscous fluid between the article and the surface.

The initial positioning of the supporting rods v 40 within the bores 28 constitutes, in, effect, a coarse adjustment for the diamond rests 44 and means are provided whereby after such-positioning of the rods 40, an extremely fine adjustment of the position of these diamond rests may be attained, the means for effecting such a fine adjustment being best illustrated inFigs. l and 2. At will be described presently, means are provided forselectively imparting independent compound movements to the diamond rests involving both horizontal and vertical vincrements of displacement. The ultimate plane established by such adjustment of the position ofeach diamond rest is, of course, a function only of the vertical components of displacement applied to the rest and the horizontal component of displacement imparted to the rest is only incidental to the attainment of the vertical displacement.

Referring now particularly to Figs. 1 and, 3, the block 22 is provided with an inclined slot 50 adjacent each apex thereof which extends upwardly from the underneath face of the block to a region not, far removed from the upper face of the block where, it communicates with a horizontally extending bore 52 which passes traversely through each arm 24. The horizontal bores 52 intersect the vertical bo-res 28 as clearly shown in Fig. 3. For convenience of manufacture, the .bore 52 may be drilled in the block 22 prior to formation of the slots 50 and thereafter the slots may be, cut in the block by means of a band-saw which is ultimately guided into the bores 52 at which region the band-saw operation terminates.

The provision of the bores 52 and slots 50 previously referred to establishes in effect an adjustable leg portion 54 at the outer end of each arm 24. Since each of the arcuate slots 50 involves a definite removal of metal during the machining operation and therefore is possessed of appreciable width, each leg portion 54 is capable of limited swinging, movement toward and away from the body of the block 22 aboutan effective. horizontal axis such as has been designated by the dotted lines x-x in Fig. 1, the center of swinging movement being located somewhat above the axis of the bore. 52. Each leg 54 effectively encompasses its respective rod 40 at least throughout a major longitudinal extent of the latter and therefore, as the leg is swung inwardly or outwardly as the case may be, tilting movement of the rod 40 about the axis xx will result. Asa consequence the position of the diamond rest 44 will be shifted in an arcuate path such as has been designatedby the dotted arc yy of Fig. 2. Due to the inherent resilience of the material from which the block 22 is formed, each leg will normally be maintained spaced from the body of the block as shown in Fig. 3 and, in order to adjustably control the angular disposition of theleg 54', an' ad justing screw 56 passes through an opening 58 provided 6 in one clamping arm 32, has its head countersunk in theopening and its shank threadedlyreceived in a socket 55,9 provided in the main body of the block 22. Thus it will be seen that upon tighteningof the screw 56 the leg 54 will be tilted about the axis x--x so as to cause the diamond rest 44 to sweep through the arcuate path y-y.

The geometry of the movement of the diamond rest, ,upon such adjustment of. the adjusting screw 56 is diagrammatically illustrated in Fig.7 wherein a right angle triangle having sides a, b, c and angles A, B, C and a rectangle having sides a, d, v and e are employed to illustrate the trigonometrical functions involved upon displacement of the diamond rest 44. In the schematic representation of Fig. 7, the distance h represents the distance from the axis x-x to the point 46 of contact of the diamond rest with the surface of the lap plate 14 or, in other words, the length .of the leg 54. This distance may be assumed to'be five inches. Assuming now that the pitch of the threads on the adjusting screw 56 issuch that there are fifty threads to the inch, a single complete turn of the adjusting screw in an effective direction will cause corresponding displacement of the leg 54 so that it assumes the position represented by the side .0 of the triangle of the Fig. 7 and wherein the diamond rest is displaced laterally the distance a or approximately .02 inch. The distances represented in Fig. 7 are only approximate since the height of the adjusting screw 56 above the effective contact point 46 of the diamond rest 44 has not been taken into consideration and also since there may be a slight shifting of the efiective axis of swinging movement of the leg 54. The approximations employed are however sufficient to illustrate the principles involved.

The displacement of the diamond-rest 44 occasioned by a. single turn, of the adjusting screw 56 is represented by the dotted arc yy (see also Fig. 3) and the diamond rest moves vfrom its initial position at 46 to a new position designated 46. This displacement involves the horizontal component a and the vertical component v and it is this latter component of motion that is of interest since it represents the vertical displacement of the diamond rest and the consequent alteration of the angularity of the plane common to all three of the diamond rests associated with the fixture 10. The angle A of Fig. 7 is highly exaggerated in order that the distance v maybe visualized in the diagram. Actually the angle A is on the order of lessthan a second of angular extent.

It isobvious that in the diagram of Fig. 7

' c=b+d=h also: v=d

in order to 'find'the distance v in terms of the known quantities h and a, it is only ,necesary to find the distance d which is equal to it.

Solving for d geometrically:

b '2 2. b /h a a'=h /ha since h=2 inches and d=.02 inch It will beseen from the above solution that if one complete turn of the adjusting screw 56 results in a .0004 inch vertical displacement of the'diamond rest 44, a small ad- 'justment' of the screw through one or two degrees only "will be capable of effecting a vertical adjustment of the rest which is measured in the millionths of an inch and which thus approximates the wave length of light.

to the plane of the surface 26. One or more articles may then be secured to the surface 26 by wringing them onto this surface in the manner previously described. The fixture is then placed within the conditioning ring 18 and the articles will bear against the lap surface with the weight of the fixture on the articles and serve to support the fixture in an elevated position so that the rests 44 will be elevated from the lap surface. The lapping operation is thus commenced and, as the lap plate rotates relative to the articles, the thickness of the articles is gradually reduced until such time as the diamond rests 44 move into contact with the lap surface 16.

As the rests 44 closely approach the surface 16 they will move into the path of the grit particles on the rotating surface and displace the same thus leaving visible tracks on the lap surface which will indicate to the operator that lapping operations are approaching completion. The progress of lapping operations may thus be observed from the time the first rest closely approaches the plane of the lap surface through such time as the second rest and finally the third rest moves into close proximity of the lap surface.

It will also be understood that no appreciable amount of lapping or wearing away of the diamond rests or of the lap surface itself will take place. In the first place, no efiiective lapping of the first two diamond rests to descend upon the lap surface will occur and when the third and last rest moves onto the plane of the lap surface, lapping operations are complete and may be terminated. With careful placement of the articles on the surface 16 so as to place the composite center of the articles at or near the center of the triangular area defined by the rests or apices of the triangle, the descent of the three rests may be almost simultaneous so that the time interval between contact of the first rest and the last rest with the lap surface is of extremely short or negligible duration. More important, however, is the fact that the hardness of the diamond rests relative to the hardness of the lap surface, coupled with their relatively broad effective surface areas is such that even with the full weight of the fixture being distributed among the three rests, no noticeable wearing of the lap surface will take place.

While the physical phenomena responsible for such lack of wear of the lap surface is not exactly understood, it is believed that the failure of the diamond material to yield to Wear results in actual descent of the plane face of the diamond rest into intimate contact with the lap surface. In other words, the plane supporting face of the rest actually moves below the level of the grit particles and the particles are thus pushed aside so to speak so that there is an absence of grit particles between the face of the diamond rest and the face of the lap surface. The rest thus slides on a clean lap surface and no wear of either the rest or of the lap surface takes place. At the same time the presence of circular swaths where the three rests or stops come into contact with the lap surface will indicate to the operator that lapping operations are complete so that he may terminate the operation of the machine. Thus at no time during effective lapping operations on the articles are all three diamond rests in contact with the lap surface.

In the lapping of crystals such as are shown at A, the articles will first be lapped on one side to provide a perfectly flat surface which may or may not be parallel with its opposite surface. The lapped surface will then be wrung on the surface 16 of the block 22 as described above and the unlapped surface then operated upon in accordance with the above procedure to cause it to be lapped perfectly fiat and parallel with the first surface. Obviously, if the lap is not perfectly fiat, then the surfaces of the article A likewise will not be fiat so that it is imperative for high precision work to maintain the surface of the lapping plate 14 as fiat as possible.

in the placement of crystals such as those shown at A in Fig. 1 on the underneath surface 26 of the lapping plate 14, it has been found that generally good lapping will take place'if the crystals are mounted on the surface 26 so as to he completely within the triangular area bounded by a series of straight lines passing through the diamond rests 44.

Referring now to Figs. 4 and 5, a modified form of fixture suitable for use in the lapping of optical prisms such as binocular prisms, or of gauge blocks or the like has been shown. In this form of the invention, only the shape of the fixture body has been altered to accommodate the placement of articles thereon while the diamond rests and their adjusting means remain substantially the same as in the form of the invention shown in Figs. 1 to 3 inclusive. To avoid needless repetitious description, similar characters of reference have been applied to the corresponding par-ts in the illustration of the two forms of the invention and new reference characters applied only where significant departures take place.

Referring now specifically to Figs. 4 and 5, the fixture 12 is in the form of a block 60 of irregular configuration including a main body portion 62 provided with laterally projecting legs 64 and 66 which extend from the body 62 in parallelism and in the same direction. A third leg 68 on the opposite side of the body 62 projects laterally from the body. Split bores 28 are provided in the three legs 64, 66 and 68 and receive therein supporting rods 49 identical with the supporting rods shown in connection with the fixture 10. Each supporting rod carries a diamond rest 44 (Fig. 5) and is capable of tilting adjustment in a manner identical with that previously described in the fixture 10.

The block 60 is provided with an inclined supporting surface 70 which extends between the legs 64 and 66 and which is adapted to receive thereagaiust one face 72 of an article A such as the optical prism shown in dotted lines in Fig. 5. The prism A may have a surface '74 which it is desired to lap to a high degree of flatness so as to bring the same into coincidence with a plane which assumes a definite predetermined fixed angle, as for example 60, with respect to the face 72 thereof.

The operation of the fixture 60is substantially the same as that of the fixture 10 shown in the previously described form of the invention. The fixture 60 may be placed within a conditioning ring such as the ring 18 of Fig. 2 and applied to the lap surface in the usual manner of lapping and it will be seen that when the three diamond rests 44 have all moved into contact with the rotating surface of the lap plate, the desired degree of prism angularity will have been applied to the face 74 of the prism or other article A.

Referring now to Fig. 6, a modified form of the adjusting means shown in connection with the fixtures id and 60 previously described has been illustrated. This adjusting means is capable of considerably finer adjustrnent than is the previously described adjusting means. To illustrate the latter adjusting means, a fixture 100, which is substantially identical with the fixture 6%) has been shown. The adjusting means shown in Fig. 6 is similar in many respects to the previously illustrated adjusting means. In the drawings similar reference characters have been applied to corresponding parts to avoid needless repetition of description.

The fixture is in the form of a block 62' similar to the block 62 and each individual adjusting means is provided by the formation of a vertical split bore 28 in which the supporting rod 40' is clamped by means of the clamping screws 34'. The curved slots 50, instead of extending upwardly from the underneath face of the block, extend downwardly from the upper face of the block to a region not far removed from the lower face of the block where they communicate with the horizontally extending bores 52'. The adjusting screws 56 are consequently located near the upper face of the block 100 while the effective tilting axes xx' about which the swinging leg portions 54' are adapted to move are located adjacent the underneath surface of t he block. The

geometry of the movement of each diamond rest 44',

upon adjustment of the adjusting screw 56 is diagrammatically illustrated in Fig. 8. In this figure the two right angle triangles having sides a, b, c and a", b" and respectively are employed to illustrate the trigonometric functions involved upon displacement of the diamond rest 44. It is not deemed necessary to enter into algebraic equations to measure the small vertical displacement v occasioned upon the lateral displacement e of the diamond rest 44 and the diagram will visually indicate that the comparative large displacement represented by the side a when the adjusting screw 56' is turned throughout one complete turn will be accompanied by a much smaller displacement a" of the diamond rest. This latter displacement at results in an extremely small vertical displacement v. If it is assumed that the distance from the axes x'x to the plane of the adjusting screw 56' be 2 inches and that the distance from the axis x-x to the point of contact 46' of the diamond rest 44 with the surface'of the lap plate be inches, the corresponding diminution in the value of the vertical displacement v from the value of the vertical displacement v shown in Fig. 7 will be A; of this former value. The displacement v' may therefore be even less than the wave length of light.

In the forms of the invention previously described, the adjusting screws 56 and 56 are shown as having their end regions threadedly received with the main body portion of the article holder with the shanks passing loosely through the leg portion. Thus upon turning of the adjusting screw in one direction the leg portion will be drawn inwardly of the fixture to decrease the width of the slot during movement of the diamond rest in its arcuate path. In Fig. 9 the adjusting screw 56a is shown as being threadedly received through the leg portion 54a with its end bearing against the remote side of the arcuate. slot 50a. It is obvious that upon turning movement of the adjusting screw 56a in one direction, the leg portion 54a will be moved away from the main body portion of the block so as to cause the diamond rest 44a to be swung outwardly away from the block in an arcuate path.

The invention is not to be limited to the exact arrangement of parts shown in the accompanyingdrawings or described in this specification, since various changes in the detail of construction may be resorted to without departing from the spirit of the invention. For example, while the invention has been illustrated herein in connection with a conditioning ring such as the conditioning ring 18 which is restrained against revolution about the lap surface, any of the fixtures shown herein may be adapted for application to the lap surface and for restraint thereon independently of whether any conditioning ring is or is not employed. For this purpose a vertical bore such as the bore 20 of Figs. 1 to inclusive, or the bore 20' shown in Fig. 6 may extend centrally through the respective fixture for reception therein a centering pin (not shown) associated with the lapping machine framework, and by means of which the fixture is restrained against revolution about the. axis of the lap while at the same time permitting rotating of the fixture upon the lap. Only in so far as the invention has been pointed out in the accompanying claims, is the same to be limited.

What is claimed is:

1. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder comprising a solid block of metal provided with a surface to which an article to be lapped is adapted to be afiixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, three limit stop members mounted on the holder and designed for ultimate contact with the lap surface to thus determine the extent of lapping operations performed upon the article by providing a three-point support for the holder and article aifixed thereto, adjusting means for one of said limit stop members to vary the position thereof, said means comprising a supporting leg capable of swinging movement relative to the body of the holder about a horizontal axis, said adjustable limit stop member being carried at the free end of said leg, and means for adjusting the angular position of said leg relative to the body of the fixture.

2. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder having a surface to which an article is adapted to be atfixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, a limit stop member mounted on the holder and designed for ultimate contact with the lap surface to thus determine the extent of lapping operations performed upon the article by providing a support for the holder and article afiixed thereto, said limit stop member being movable in an arcuate path relative to the body of the holder about a horizontal axis whereby said member may have both horizontal and vertical components of movement, and means for adjusting position of said stop member in its arcuate path of movement.

3. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder including a body portion provided with a surface to which an article to be lapped is adapted to be aflixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, three limit stop members mounted on the holder and designed for ultimate contact with the lap surface to thus determine the extent of lapping operations performed upon the article by providing a three-point support for the holder and article afiixed thereto, a supporting leg for one of said limit stop members, said leg being integral with said body portion and oscillatable relative to the latter about a horizontal axis, said limit stop member being carried at the free end of the supporting leg, and means for adjusting the angular position of said leg relative to the body portion of the article holder whereby the vertical component of movement of the limit stop member will be a function of the sine of the angle of displacement of the limit stop member.

4. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder including a body portion, means on said body portion for supporting an article in fixed position whereby the article may be applied to said movable lap with the weight of the holder resting upon the article, three limit stop members mounted on the holder and designed for ultimate contact with the lap to thus determine the extent of lapping operations performed upon the article by providing a three-point support for the holder and article, and a supporting leg for one of said limit stop members oscillatable relative to the body portion of the holder about a horizontal axis, said latter limit stop member being carried at the free end of said leg, and an adjusting screw extending through said leg and threadedly received in said body portion for adjusting the angular position of the leg.

, 5. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder including a body portion, and a leg portion carried by said body portion and oscillatable relative thereto about a horizontal axis, means for securing an article to the holder for application to the lap surface of the machine with the weight of the holder supported upon the article, a limit stop member mounted on the free end of said leg portion and designed for ultimate contact with the lap surface to thus determine the extent of lapping operations performed upon the article by providing a support for the holder, and means extending through one of saidmembers and threadedly received in the other member for adjusting the angular position of the leg portion relative to the body portion.

6. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder including a body portion,

and a leg portion carried by said body portion and oscillatable relative thereto about a horizontal axis, means for securing an article to the holder for application to the lap surface of the machine with the weight of the holder supported upon the article, a limit stop member mounted on the free end of said leg portion and designed for ultimate contact with the lap surface to thus determine the extent of lapping operations performed upon the article by providing a support for the holder, and an adjusting screw extending loosely through one of said members and threadedly received in the other member for adjusting the position of said leg portion relative to said body portion.

7. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder including a body portion, and a leg portion carried by said body portion and oscillatable relative thereto about a horizontal axis, means for securing an article to the holder for application to the lap surface of the machine with the weight of the holder supported upon the article, a limit stop member mounted on the free end of said leg portion and designed for ultimate contact with the lap surface to thus determine the extent of lapping operations performed upon the article by providing a support for the holder, and an adjusting screw extending through and threadedly received in said leg portion and bearing against said'body portion for adjusting the position of the leg portion relative to the body portion.

8. In a machine for lapping aface on an article, means providing a lap surface, an article holder, means establishing relative movementbetween said article holder and lap surface, said article holder, a surface to which an article is ada'ptedtobe afiixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, said holder comprising a solid block of metal having a relatively deep slot formed therein dividing the holder into a main body portion and a leg portion capable of bodily swinging movement relative to the body portion about a horizontal axis, a limit stop member carried at the free end of said leg portion, and means for adjusting the angular position of said leg portion relative to said body portion.

9. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder having a surface to which an article is adapted to be affixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, said holder comprising a solid block of metal having a relatively deep slot formed therein dividing the holder into a main body portion and a leg portion capable of bodily swinging movement relative to the body portion about a horizontal axis, a limit stop member carried at the free end of said leg portion, and means for adjusting the angular position of said leg portion relative to said body portion, said adjusting means comprising an adjustable screw passing through said leg portion and threadedly received in said body portion.

10. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder having a surface to which an article is adapted to be affixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, said holder comprising a solid block of metal having a relatively deep slot formed therein dividing the holder into a main body portion and a leg portion capable of bodily swinging movement relative to the body portion about a horizontal axis, a limit stop member carried at the free end of said leg portion, and means for adjusting the angular position of said leg portion relative to said body portion, said adjusting means comprisingan adjusting screw passing through and threadedly received in said leg portion and bearing against said body portion.

1]. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder having a surface to which an article is adapted to be aflixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, said holder comprising a solid block of metal having a relatively deep slot formed therein dividing the holder into a main body portion and a leg portion capable of bodily swinging movement relative to the body portion about a horizontal axis, a limit stop member carried at the free end of said leg portion, and means for adjusting the angular position of said leg portion relative to said body portion, said adjusting means comprising an adjusting screw passing through and threadedly received in one of said portions and bearing against the other portion.

12. In a machine for lapping a face on an article, means providing a lap surface, an article holder, means establishing relative movement between said article holder and lap surface, said article holder havinga surface to which an article is adapted to be affixed and by means of which the article is applied to the lap surface with the weight of the holder supported upon the article, said holder comprisinga solid block of metal having a relatively deep slot formed therein'dividing the holder into a main body portion and a leg portion capable of bodily swinging movement relative to the body portion about a horizontal axis, there being a substantially vertically extending bore formed in said leg portion, a supporting rod adjustably secured in said bore and having one end thereof projecting outwardly thereof, a limit stop member mounted on the projecting end of said supporting rod, and means for adjusting the angular position of said leg portion relative to said body portion.

References Cited in the file of this patent UNITED STATES PATENTS 338,322 Waters Mar. 23, 1886 1,192,416 Graves July 25, 1916 2,363,544 Mogey Nov. 28, 1944 2,397,860 Hodgdon Apr. 2, 1946 2,412,306 Stoll Dec. 10, 1946 2,565,590 Bullard Aug. 28, 1951 2,627,144 Roshong Feb. 3, 1953 2,722,089 Boettcher Nov. 1, 1955

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