US2195064A - Lapping apparatus and method - Google Patents

Description

March 26, 1940. D. A. WALLACE LAPPING APPARATUS AND METHOD Filed Sept. 23, 1958 2 Sheets-Sheet 1 11v VEAZTOR fill [Z )7: flQ/Zace,

A TTORNE Y5.

March 26, 1940. v D. A. WALLACE 2,195,064,,

LAPPING APPARATUS AND mmaon Filed Sept. 23, 1938 2 Sheets-Sheet 2 72 E- 2 7, I'E 2 75 72 7/ 11;" r

33 Sig i v V l E-E- ATT R Patented Mar. 26, 1940 uNirEo STATES PATENT OFFICE Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Application September 23, 1938, Serial No. 231,404

24 Claims.

Thisinvention relates to an improved apparatus for and method of finishing surfaces.

The purpose of finishing operation is to eliminate theirregularities of comparatively minute dimensions which result from variouscauses such as wear, corrosion and particularly from operating upon surfaces of diverse contours with grinding, machining or other material removing tools of the type which are used to shape and to bring articles to predetermined dimensions. Under microscopic examination, tool marks are found to comprise ridges or serrations of somewhat regular'spacing and depth and are gener: ally triangular in cross section with their vertices extending outwardly from the body of the article. At the bottoms'of the ridges of greatest depth is the so-called continuous base material section to which the ridges must be substantially removed without introducing scratches in order to produce a perfect surface substantially free from grinding and machining marks and father irregularities.

Briefly, this is accomplished in the practice of my improved finishing method by applying to 25 the work a suitable abrading element and producing components of relative movements of a comparatively low rate of feet per minute between the abrading element and the work which results in a, scrubbing action on the work surface without heating the latter to a ductile state, this scrubbing action being performed while the work and abrading element are urged together with a relatively low pressure and in the presence of a lubricating coolant which will, under such pressure, hold the protruding, active particles of the abrading material against scratch forming and further cutting contact with the work at the continuous base material section thereof.

One of the main objects of the invention is the provision of a finishing method and apparatus of this kind by which ridges resulting from grinding, machining and other previous operations on the surface of a piece of work may be removed substantially to the continuous base material section of such surface in a high'speed, production manner and without introducing finishing formed scratches or other irregularities.

A further object of the invention isthe provision of an improved finishing method and apparatus during the operation of which abrading of the material operated upon discontinues as soon as the ridgesare removed and no appreciable dimensional change takes place upon continuation of the operation beyond this stage.

Another object of the invention is the provision in a finishing. apparatusand method for guarding against heating of thecoolant and accompanying lowering of its viscosity, and heating of the outer skin of a work surface to a state such that it is rendered susceptible of being scratched during finishing, by suitably controlling the rates of the component relative movements of the work and abrading element, the abrading character of the element, the pressure with which it is urged against the work surface and the viscosity of the lubricating coolant'applied thereon.

A further object of the invention is the provision of a finishing method and apparatus of this kind by which mainly all machining, grinding and otherwise formed ridges and projecting disfigurations of a surface are abraded substantially to a common line at substantially all cross sections of the surface so'that any irregularities which remain comprise only widely spaced indentures from the surface formed by the common extremities of the abraded ridges which are adapted to serve as lubricant reservoirs.

An additional object of the invention is the provision, in a finishing method and apparatus of this character, for cyclic variation of the speed of one or more of the components .of relative abrading movements of the work and abrading element as wellas a variation of the relative feed movement of the work and the abrading element in order to further guard against scratch forming operation of vthe abrading element on the work surface and to cause successive resultant relative movements of the work and abrading element to occur in different directions.

A still further object of the invention is the provision, in a finishing method and apparatus of this kind, for cyclic variation of the pressure I of application of the abrading element to the work.

Additional objects of the invention are to provide an improved finishing apparatus for cylindrical surfaces which is particularly adapted for finishing rolls of large and diverse diameters; to provide in finishing apparatus of this kind a tool having a plurality of independently reciprocably operable abrading elements which successively operate upon substantially the same increments of the work surface during each relative rotation of the work and abrading element; to provide means for reciprocating such abrading elements throughout different lengths of stroke and at different speed; to provide a plurality of abrading element carrying tools in apparatus of this kind which are shiftable in a' converging course to accommodate adaptation of 55 the tools to cylindrical pieces of work of diverse dimensions; to provide means for selectively urg ing such tools independently toward thework with a constant or varying pressure respectively, of the same or different values; and to provide fluid pressure actuated mechanism for urging the abrading elements against the work which is adapted to cause such elements to follow the slightly longitudinally rolled contour of rolls of the type used in metal rolling processes.

Other objects of the invention are the provision of means for so mounting a tool of this character and a roll machine bed as to facilitate convenient performing of finishing operations on one or more rolls, for example of the large variety used in metal rolling processes, while such rolls are mounted on their normal bearing supports and without requiring dismantling of the rolling machine; and to provide a finishing tool of this kind which may be supported by a structure independent of a roll machine bed and conditloned to finish both the bearing surfaces and operating surfaces of a roll.

Illustrative embodiments of the invention are shown in the accompanying drawings, in which:

Fig. l is an enlarged diagrammatic sectional view of a piece of work having a surface to be finished.

Fig. 2 is a view, similar to Fig. 1, of the work shown therein after it has received a finishing operation embodying the invention.

Fig. 3 is a side elevational view, partly in section, of apparatus embodying the invention and by which the improved finishing process may be practiced.

Fig. 4 is a transverse sectional the line 4-4 of Fig. 3.

Fig. 4A is a. transverse section taken on line 4A-4A of Fig. 3.

Fig. 5 is an enlarged longitudinal sectional view of one of the tools of the apparatus illustrated in Figs. 3 and 4, taken mainly on the line 55 of Fig. 3 and shown in section the pressure exerting mechanism associated therewith.

Fig. 6 is a fragmentary view similar to Fig. 5 but illustrating a tool embodying a modified form of the invention.

Fig. 7 is a vertical sectional view of a rolling machine equipped with roll finishing apparatus embodying the invention and by which the improved finishing method may be practiced.

Fig. 8 is a side elevational view of apparatus by which the speed of operation of the driving motors of the apparatus may be cyclically varied.

Fig. 9 is a transverse sectional view taken on the line 9-9 of Fig. 4A.

In practicing the improved finishing method, a piece of work having a surface to be finished and an abrading element comprising natural stone or compressed particles of suitable grit are mounted for contacting relative abrading movements with respect to each other. When operating upon cylindrical surfaces of a piece of work, the latter is preferably drivingly rotated while the abrading element is reciprocated relative to the work in the direction of its rotative axis. In finishing fiat or end surfaces, the work may be rotated about an axis intersecting such surface while the abrading element is reciprocated radially of such'an axis. Internal cylindrical surfaces may be finished by simultaneously rotating and reciprocating an abrading element while the latter is yieldably held in abrading contact therewith. Various types and directions of component movements may be employed to derive a desired view taken on resultant relative movement between the work and an abrading element.

The pressure with which the abrading elements are urged against the work surface being finished and the rate of the resultant movement between the work and the abrading element are maintained at low values as compared with the pressures and rates of relative movement employed in grinding, machining, honing, turning and other conventional operations during which substantial material is removed from the work., In finishing surfaces of work comprising cast iron, steel or aluminum, for example, finishing pressures of from 15 to 16 pounds per square inch are preferably employed, pressures of 30 pounds per square inch, or less, being satisfactory. The relative rotative movement of such work and the abrading element is preferably held at a rate of 35 to 50 feet per minute, 50 feet per minute or less being satisfactory, and the rate of relative reciprocatory movement of the work and abrading element is preferably 15 to 25 feet per minute, satisfactory results being attainable at 50 feet per minute or less. Such finishing operations may be performed with abrading elements or stones of 500 mesh grit in the presence of an oil having a viscosity of 460 seconds Saybolt at 100 F.

The rate of the resultant relative movement between the work and the abrading element and the pressure with which the latter is urged against the work is sumciently low to prevent heating of the skin of material at the surface operated upon to a state of scratchable ductility. When excessively high pressure and speeds are employed, there is found to be an instantaneous rise in the temperature of the increment of surface under operation, in some cases to temperature of 600 to 700 F., which results in scratching thereof by the particles of grit of the abrading element.

Essentially, the finishing operation comprises removing all irregularities which project above a predetermined base line l2, as illustrated in Fig. 1, without, while so doing, causing any additional irregularities by removing any portion of the material below the base line l2. As the abrading element is moved into engagement with the surfaceto be finished it first engages thetops of the ridges l0. As the abrading element is held in engagement with the surface to be finished with a predetermined pressure, the unit pressure between the tops of the ridges and the abrading element will be very high and the rate at which the tops of the ridges are removed by transverse movement of the abrading element is consequently high. As the tops of the ridges are removed the abrading element engages portions of the ridges of gradually increasing area, which causes a reduction in the unit pressure therebetween and consequently a reduced rate of cutting or removal of material, which is, of course, desired, as the line I2 is approached. The area of the material in engagement with the abrading element, and consequently being removed, continues to increase as the base line I? is approached, and the unit pressure between the relatively movable surfaces correspondingly decreases.

As is well known, when oil is applied to any surface, it forms a film of oil thereon which causes any other surface in engagement therewith to slide freely thereon provided that the unit pressure therebetween is not sufficiently great to rupture that oil film. in which event the two surfaces are in direct engagement, with resulting friction. The strength or the oil film varies with the viscosity of the oil and with the temperature there- In order to take advantage of this fact, oil is applied to the surface being finished, the oil employed being of such viscosity that the unit pressure between the abrading element and the surface is sufficiently great to rupture the oil film when the abrading element engages the tops, and later the intermediate portions, of the ridges II], but which is insuificient to break the oil film as the base line I2 is reached, thus causing the abrading element to engage and reduce the height of the projections until such time as the gradually falling unit pressure is insufficient to break the oil film, after which it slides freely thereover.

Obviously the pressure applied to the abrading element must bear such relation to the contacting area thereof and to the viscosity of the oil employed that the oil film will be broken thereby until the desired degree of smoothness of surface has been attained and after which the oil film will present an unbroken surface over which the abrading element will slide freely without removing any further mater al. In addition, the irregularity of the contacting surface of the abrading element must be taken into account in determining the pressure applied thereto so as to maintain the unit pressure in the correct relationship with the strength of the oil film. If

the unit pressure is too high with respect to the 1 viscosity of the oil, so that the oil film is ruptured at the minimum unit pressure, the abrading element will continue to remove material after the base line 12 has been reached, which is, of course, undesirable, and if the unit pres- .sure is too low with respect to the viscosity of the oil, only the tops of the ridges will be removed, I

and a poorly finished surface results.

In highly accurate finishing operations it is desirable to maintain the oil, which also serves as a coolant to prevent local hot spots, at a uniform predetermined temperature, the strength of the oil film decreases as the temperature of the oil increases.

With proper control of the unit pressure and the strength of the oil film, the degree of fineness of finish may be varied within considerable limits.

Although I have referred, in both the specification and claims, to employing oil to prevent abrading the surface to be finished beyond the desired degree, it is apparent that any other material may be employed for this purpose which will form, and readily reform, a protective film or coating which will, within practical limits, resist rupture and beyond these limits permit rupture and direct contact between the abrading element and the surface being finished.

While numerous types of relative abrading movements of the work and abrading element may be employed, the foregoing combination of rotative and one or more reciprocative movements is preferable. The rates of any or all of these component movements may be cyclically varied, and if a feeding movement of the abrading element carrying tool is practiced, therate of this movement may also be varied cyclically duringthe finishing operation. Since the direc-- surface of the work to be traversed by relative movements in a plurality of directions. The

cyclic variation of one or more of the com 'ponent movements may be relied upon to vary the direction of the successive resultant movements occurring during alternate half cycles of the relative reciprocatory movement.

In the drawings is illustrated one type of lapping apparatus embodying the invention and by which the improved lapping method may be performed. The lapping apparatus shown in the drawings is particularly adapted for the lapping of cylindrical surfaces of large rolls 14 of the type used in the metal rolling, paint manufacturing and paper manufacturing industries, for example.- Obviously apparatus of substantially the same construction and of different dimensions may be employed in the lapping of external surfaces of bearings, journals and various articles of diverse sizes. The lapping apparatus illustrated includes a frame structure comprising a pair of vertically upstanding supports l5 and I6 between which is located a pair of hydraulic jacks l1. Each jack l1 includes a piston portion I8 and an externally extending piston rod portion IS on which is rotatablymounted at 20 two spaced pair of rollers 2|. The rollers 2| are arranged, as illustrated in Fig. 3, to receive bearing portions 22 provided at the opposite extremities of the roll it. The hydraulic jacks I! may be manipulated in a conventional manner to bring the axis of the roll M to a desired elevation and condition of level. The roll l4 may be independently supported during the lapping operation by the jacks H or it may be rotatably mounted, if desired, upon centers 23 and 24 provided on the vertically upstanding supports it and [6 respectively. I

The roll It is adapted to be drivingly rotated by a driving member 25 rotatably mounted-in a bearing plate 26 which is secured to the left side of the support l6, as viewed in Fig. 3. The driving member 25 is provided at its left end, as viewed in Fig. 3, with a chuck 21 in which is received eitherthe normal bearing 22 of the roll it or an outwardly extending portion 28 thereof.

The chuck 21 is adapted to firmly grip the projection 28 of the roll for the purpose of drivingly rotating it. Theright end portion of the driving member 25 is provided with a worm gear 29-located withinthe g'ear housing 30. mounted on the support I6. This worm gear meshes-with a worm 3| located within the gear housing 30 and between spaced abutments 32 therein. A drive shaft 33 is splined within the worm and it is connected at its lower end by a coupling 35 to a shaft 36 of a combined motor and transmission gear unit generally designated by the numeral 37, as shownin Fig. 4A. The transmission mechanism 38 of the unit 3? preferably comprises eccentric gearing by which the rotative speed of the shaft 36 and driving member 25 are cyclically variedwithin predetermined limits. This eccentric gearing comprises an elliptical pinion 36' on the shaft 36 which is meshed with an elliptical pinion 3i driven 'by the motor 3'8. Cyclic variation of the rotative speed of the roller [4 may be accomplished in the foregoing manner or without the use of eccentric gearing by interposing suitable circuit control mechanism (not shown) in the circuit 39 of the electrical motor.

The upper end portions of the supports l5 and I 6 are provided with horizontal seats 40 for .re-

which are connected together at their opposite end portions by transverse cross members 42. The cross members 42 have upstanding eyes 43 secured thereto by which the guide rails may be conveniently lifted from the seats 48 with the aid of conventional cranes customarily employed in shops equipped to handle rolls of the type illustrated at M.

Shiftably mounted on the guide rails 4| is a tool carriage generally designated by the numeral 44 in Fig. 3. This tool carriage comprises a frame structure 45 having opposite side flanges 46 on which are rotatably mounted a pair of rolls 41 adapted to engage the lower edge portion of a rail 4| and a roll 48 located between the rolls 41 which is adapted to engage the upper edge portion of a rail 4|. The carriage 44 is adapted to be reciprocably fed longitudinally on a roll H by a pair of screws 49 threaded in apertures formed in the opposite flanges 46 in the carriage.

The rear ends of the screws 49 are journalled in an aperture formed in a cross member 50 extending between the guide rails 4| which is secured to the latter. The right end portions of these screws are journalled in apertures formed in cross member 52 which also extends between rails 4|. One of the screws 49 is connected to be driven by a .shaft of a reversing motor 53 carried by the rails 4| and the other screw 49 is drivingly connected by a chain of gearing (not shown) so as to be driven in unison therewith. The reversing motor 53 may be operated at a constant speed or its speed of operation, and accordingly the speed of operation of the screws 49, may be cyclically varied by interposing in the electrical circuit 54 thereof suitable circuit control apparatus for cyclically changing current or voltage of the circuit 54. The reversing motor 53 may be relied upon to drivingly feed the tool carriage 46 back and forth over the surface of the roll I 4 operated upon.

Provided in the frame structure 45 are a plurality of arcuately arranged bearings 55, 56 and 51 in which lapping tools, generally designated by the numerals 58, 59 and 60, are shiftably supported. The bearings 55. 56 and 51 are preferably so constructed and arranged as to confine shifting movement of the tools 58, 58 and 68 in courses which converge substantially at the axis 6| of the roll l4. 1

The tool 58 includes a casing 62 of rectangular cross section in which is mounted a pair of oscillatable levers 63 which are pivotally supported on a common pin 64 carried by the opposite side walls of the casing 62. The upper end portion of each lever 63 is provided with an enlarged head 65 having a slot 66 extending substantially parallel to the axis of the pivot pin 64. A block 61 is mounted on the upper end of the casing 62 and provided with a central aperture through which extends a driving shaft 68 or a combined motor and transmission gear unit generally designated by the numeral 69. The transmission gearing of this unit may comprise eccentric gearing by which the rotative speed of the shaft 69 may be cyclically varied. If desired, the shaft 69 may comprise the shaft of an electric motor having a circuit in which is included voltage or current varying apparatus by which the speed of operation of the motor may be directly cyclically varied. The drive shaft 68 has an end portion located within the casing 62 on which is fixed a gear 10. The gear 18 meshes at diametrically opposite extremities with pinions 1| having upwardly extending hub portions 12 joumalled in apertures formed in the block 61. Each pinion 1| has an eccentric roll 13 depending downwardly therefrom and received in the slot 66 of one of the oscillatable levers 63.

The lower end of each oscillatable lever 63 is provided with an abrading element holder 14 in which are mounted abrading elements 15 comprising natural stone or compressed particles of grit. These abrading elements may be comprised of materials of the type conventionally used in honing operations. The abrading element holders 14 are provided with a pair of upstanding flanges 94 between which the lower extremities of the levers 63 are received and to which the latter is pivotally attached by a pin 95 extending transversely of the rotative axis of the roll l4.

The abrading elements 15 are adapted to engage the surface of the roll H or other piece of work to be flnished and these abrading elements are preferably yieldably urged against the work surface by fluidpressure mechanism comprising a cylinder 16 mounted on-the frame structure 45 of the tool carriage and in which is slidably mounted a piston 18 having a piston rod 18 attached to the housing of the motor unit 68. The

piston 18 and tool with which it is connected is normally urged away from the work by a spring 18' in the cylinder 16. A flexible conduit or hose 19 communicates at one end with the upper end portion of the cylinder 16 and at its other end with a cylinder 88 which is provided with a plunger 83 having an externally projecting plunger rod 82. Slidably mounted in the cylinder 88 is a piston 8| which is normally urged upwardly as viewed in Fig. 5 by a spring 84 bearing 9 between the piston 83 and the plunger 8|. The

interior of the fluid pressure mechanism, from the piston 18 of the cylinder 16 to the piston 83 of the cylinder 80, is filled with a column of fluid medium on which is applied the expansion force of the spring 84. The action of the spring 84 may be maintained at a selected constant value if desired or it may be varied by adjustably shifting the plunger 8|. Cyclic variation of compression of the spring 84 and accordingly corresponding variation of the pressure with which the lapping elements are urged against the work by the column of fluid medium in the hose 19 may be produced by causing a cam 85 to operate upon the plunger rod 83 as viewed in Fig. 5. The cam 85 may be non-rotatably secured to a shaft 86 of a motor 81 or other suitable driving mechanism.

The pinions 1| by which the osclllative levers 63 are actuated may be of the same size or one of these pinions may be of larger diameter than the other as illustrated in the drawings. A difference in size of the pinion 1| will produce a corresponding difference in the speed of oscillation of the levers 63. The amount of eccentricity of the eccentrics 13 carried by the pinions 1| may differ so as to produce osclllative strokes of the same or different predetermined lengths while the number of oscillations per unit of time of both levers may be selectively predetermined by the sizes of the pinions 1|. By this construction a finishing tool is provided having a pair of independently reciprocable lapping elements which may be reciprocated throughout the same or different numbers of strokes per unit of time and throughout strokes of the sar'ne or difierent lengths.

The tool 60 is substantially identical in construction to the tool 58am! is provided with fluid pressure mechanism of the same character as that with which the tool 58 is provided for urging its abrading elements against the work. The tool 59 is similar in construction to the tools 58 and 60 but in the tool 59 is provided only a single oscillative lever 08. Either or both of the oscillative levers 63 in the tools 58 and 60 may be formed in accordance with the construction of the oscillative lever generally designated by the numeral 89 and shown in Fig. 6. One of these oscillative. levers comprises telescoping parts 90 and 9| between which is interpJsed a spring 92 for predetermining the pressure of application of the lapping elements I5 thereof upon the work.

If only one of the pair of oscillative levers of a tool such as the tool 58 comprise telescoping sections between which a spring is disposed as illustrated in Fig. 6, then the pressures by which the lapping elements of tre respective oscillative levers are urged against the work may be brought to different predetermined values and these pressures will be maintained at different values throughout cyclic variation thereof of the fore-' going type. a

Lubricant may be discharged upon the surface of the work from nozzles 91 mounted on the carriage 44 and supplied with lubricant, from a source not shown, by suitable conduits 98.

For the purpose of setting forth one specific example of the lengths of stroke and rate of reciprocation which may be used to advantage in finishing a roll surface by my improved finishing apparatus and method, the lapping elements appearing in Fig. 4 have been. designated by Roman numerals I to V, inclusive; The lengths of stroke of the elements I, II, III, IV and V may be respectively 1%, /8 and V2 inch and these abrading elements may be reciprocated at 500, 400, 300, 250 and 200 reciprocations per minute. The reciprocative rates of the abrading elements of each of the tools 58, 59 and 60, as well as the rotative speed of the work, may be maintained at constant values, or cyclically varied as heretofore set forth. Cyclic variation of the rotative speed of the work may take place while the rate of reciprocative action of the abrading elements is also cyclically varied or only either one of these cyclic variations may be practiced.

In the form of the invention illustrated in Fig. 7, the improved finishing apparatus is illustrated as a permanent part of a rolling machine generally designated by the numeral I comprising a base portion IM 'and vertically upstanding side frame members I02 between which are journalled a pair of rolls I03 and I04. Mounted on the base structure "II of the roll machine adjacent opposite longitudinal extremities is a pair of vertically upright posts I05, only me of which is shown in Fig. 7. Vertically slidably mounted on each of the posts I05 are brackets I06 which extend toward the rolls I03 and I04. Each bracket I06 is provided with a track I0I between which a finishing tool carriage, generally designated by the numeral I08, is mounted for reciprocatory movement longitudinally of the rolls I03 and I04.

'The finishing tool carriage I08 is similar in construction to the finishing tool carriage 44 shown in Figs. 3 and 4 and provided with finishing tools 58, 59 and 60 substantially identical in construction to the corresponding finishing tools shown in Figs. 3 and 4. The finishing tools of the apparatus shown in Fig. '7 are provided with fluid pressure apparatus, not shown in Fig. '7, substantially identical to that shown in Figs. 3, 4

and 5 and these tools are capable of operating in precisely the same manner as the operation described in connection with-the form of the invention shown in Figs. 1 to 6, inclusive.

The carriage I08 is provided with rollers I09 which set upon the tracks 101 so as to facilitate smooth reciprocatory movement of the carriage and finishing tools over the lengths of the rolls I03 and I04. This reciprocatory movement may be provided by a threaded shaft IIII threaded in an aperture III formed in the frame structure -of the carriage I08. The threaded shaft IIO may be drivingly operated in the same manner as the I threaded shafts 49 in the form of the invention shown in Figs. 3 and 4.

The tool carriage I08 and the tools carried thereby may be vertically adjustably positioned so as to bring theabrading elements of the tools selectively into engagement with either the roll I03 or the roll I 04, or to move the tools to'a position above the upper roll' I03 in order to avoid obstructing the access to the rolls during normal operation thereof. This adjustment of t e tool carriage I 08 and tools carried thereby may be effected by rotation of threaded shafts H2 each extending along one of the posts I05 respectively and threaded in apertures II3 formed in the brackets I 06.. 1

Cyclic variation of the speed of operation of any of the motors employed to drive either the work or the tools may be produced by the apparatus shown in Fig. 8 which includes a rheostat generally designated by the numeral I20 having a plurality of fixed contact elements I2I and a movable contact element I22 pivotally mounted at I 23. The upper end of the lever I22 is operatively connected by a link I23 with an actuating arm I24 which is pivoted at I25 on a bracket I26. Ro-

tatably mounted on the bracket I26 is a worm gear I2'I having a cam I28 non-rotatably fixed thereto and operatively engaging the lever I24 which is normally urged by a spring I in a counterclockwise direction, as viewed in Fig. 8, about its pivotal axis I25. The worm gear I21 may be driven at a constant speed by a motor I29 having a worm I30 on its shaft, meshed with the teeth of the worm gear I2'I.

This apparatus is particularly adapted for varying the supply to direct current motors of the type conventionally used in apparatus of this character. The rheostat I20 is connected in a circuit comprising an input line I3I having a conductor I32 connected with the movable contact I 22 and a conductor I33 connected with the fixed contacts I2I of the rheostat, between which are connected in series .a plurality of resistance elements I34. The conductor I33 and one of the line conductors I3I may be employed for supplying current to the motor in order to cyclically vary the speed thereof and the part of the apparatus work as the protruding portions are removed to the base line I2, as illustrated in Fig. 2. The viscosity of the lubricant film onthe work surface holds the grit of the abrading element against penetrating the film under the unit pressure existing at the base line I! and therefore the formation of finishing formed scratches is prevented.

During removal of the ridges III, the lubricant serves to carry away the abraded particles of the material of the work which are effectively unloaded from the abrading elements by the reversal in its movement during reciprocation, thus maintaining the abrading elements in efilcient cutting condition when abrading action is desired.

The relatively low rate of relative movement between the work and the abrading element assures maintaining of the temperature of the surface operated upon at substantially room temperature and far below the instantaneous temperatures existing in conventional metal removing processes during which the metal is heated to a state of scratchable-ductility. Such control of the temperature of the work surface also prevents reducing of the viscosity of the oil film thereon. The shortness of the stroke of the reciprocatory movement eliminates all possibility of the formation of scratches of substantial length even during initial stages of the finishing process when the unit pressure of application of the abrading element is of a maximum value.

The abrading factors may be so predetermined as to discontinue the cutting action before the ridges have been removed to the base line indicated at I! in Fig. 2. in instances where the surface requirements are satisfied by the condition of surface existing before the base line has been reached. The resulting surface is, however, free from finishing formed scratches, although it may still contain residual portions of the lands ll. Due to excessive depths of spaced isolated lands, some residual land portions may remain after the ridges have been removed to the base line l2 but in any event the residual lands constitute only an insignificant portion of thesmooth finished area and they serve as lubricant reservoirs when the surface is lubricated in use. The substantially continuous surface presented at the base line If differs from surfaces finished by processes and apparatus heretofore employed by which the tool formed ridges are either converted to similar ridges of smaller height and closer spacing. substituted by such smaller ridges, or polished on their sides to present only a light reflecting appearance of smoothness. Any irregularities such as the residual land portions, illustrated in Fig. 2, remaining after the finishing operation extend inwardly from the base line I! into the body of the work rather than outwardly from the base line. Such finished surfaces therefore are free from the protruding particles which heretofore, particularly in bearing and joumai structures, have had a tendency to penetrate an oil film and wear the parts with which they are.

operatively associated. This property of surfaces finished in accordance with the invention'results in longer life of both the finished parts of a. structure and the parts which operatively contact therewith. No appreciable dimensional changes are produced during removal of the ridges since their heights are so minute and cutting discontinues when they have been removed to the base line.

v Cyclic variation of one or more of the com ponent movements which contribute to the resultant relative abrading movement of the work and abradingelements causes successive resultant movements to occur in different directions and assures a variety of directional applications of the abrading element to all portions of the surface being finished. The cyclic variation of the pressure with which the abrading element is applied to the work, which is kept within limits such that abrading ceases as heretofore set forth, similarly subjects all portions of the surface under treatment to a variety of unit pressures. These variations in the abrading functions produce a scrubbing action of the abrading elements upon the work during which retracing of the same path on the work by localized large or hard particles of grit of the abrading element is effectively guarded against.

By embodying in a tool a plurality of abrading elements which are so arranged as to successively operate upon substantially the same increments of area of the work in an alternate manner as the work rotates, and by maintaining the abrading operations of the respective elements at different values, no portion of the work is so subjected continuously to the action of any one abrading element as to result in imparting to the work surface under treatment only the characteristics of any one abrading element or its mode of operation. 4

Although but several specific embodiments of the invention are herein shown and described, it will be apparent that various changes in the size,'shape and arrangements of parts may be made without departing from the spirit of the invention.

I claim:

1. The method of finishing a surface having a multiplicity of minute ridge-like projections or scratches thereon to substantially remove said projections and produce a surface substantially free from scratches which comprises moving an abrading element over said surface in engagement therewith at a predetermined speed and pressure and maintaining a film of oil on said surface of such viscosity that the unit pressure between the abrading element and the surface is sufiicient to rupture said oil film to engage and wear away the tops of any irregularities of said surface and is insufiicient to rupture said oil film during further relative moving application of said element to said surface under said pressure when said surface is substantially free from irregularities.

2. The method of finishing a surface of a piece of work which comprises the steps of supporting said work and an abrading element for contacting relative movement which is a resultant of at least two different directional component movements, drivingly cyclically producing said component movements while said abrading element is held in operative engagement with said surface of said work, and changing the ratio of the number of cycles of one of said component movementsto the number of cycles of the other by varying the rate of occurrence of one of said component movements.

3. The method of finishing a surface of a piece of work which comprises the steps of supporting a piece of work and an abrading element for relative movement which is the resultant of components of relative rotative and relative reciprocatory movement of said work and abrading element, simultaneously drivingly cyclically producing said relative component movements, urging said abrading element against said work during said relative movements, and repeatedly varying the rate of occurrence of cycles of at least one of said components between maximum and ponents of minlmum limits during said finishing operation.

4. The method of finishing a surface of a piece of work which comprises the steps of supporting a piece of work and an abrading element for relative movement which is the resultant of comcatory movement of said work and abrading element, simultaneously drivingly producing said relative component movements, urging said abrading element against said work during said relative movements, and changing the ratio of the number of reciprocative to rotative component movements by varying the speed of said reciprocatory component movements from one value to another.

5. The method of finishing a surface of a piece of work which comprises the steps of supporting a piece of work and an abrading element for relative movement which is the resultant of components of relative rotative and relative reciprocatory movement of said work and abrading element, simultaneously drivingly producing said relative component movements, urging said abrading element against said work during said relative movements, and varying of successive resultant movements of said work and abrading element by cyclically varying the rate of said rotative component.

6. The method of finishing a surface of a piece of work which comprises the steps of supporting a piece of work and an abrading element for relative movement which is the resultant of components of relative rotative and relative reciprocatory movement of said work and abradingelement, simultaneously drivingly producing said relative component movements, urging said abrading element against said work during said relative movements, and varying the direction of successive resultant movements of said work and abrading element by cyclically varying the rates of both of said component movements.

'7. The method of finishing a surface of a piece of work which comprises the steps of supporting said work and an abrading element for relative movement which is the resultant c'z'relative rotative, relative short stroke reciprocative and relative long stroke feeding component movements, drivingly producing said relative component movements, urging said abrading element against said work during said relative movements, and varyingthe directions of successive resultant movements by cyclically varying said feeding movement component.

8. The method of finishing a surface of a piece of work which comprises simultaneously applying to adjacent increments of said surface a pair of reciprocative abrading elements, drivingly reciprocating said elements at respectively different speeds, and drivingly producing such additional relative movement between said work and said elements as to cause substantially the same increment of area of said surface to be operated upon alternatelyby each of said abrading elements respectively.

9. The method of finishing a cylindrical sur-' face of a piece of work which comprises the steps of rotatively supporting said work, simultaneously applying to circumferentially spaced increments of said surface a pair of reciprocative abrading elements, drivingly reciprocating said elements at respectively difierent speeds, and alternately bringing substantially the same increments of area of said surface into operative engagement with each of said abrading elements respectively by drivingly rotating said work.

relative rotative and relative reciprothe directions 10. The method of finishing a cylindrical surface of a piece of work which comprises the steps of rotatively supporting said work, simultaneously applying to circumferentially spaced increments of said surface a pair of reciprocative abrading elements, drivingly reciprocating said elements through strokes of different length and at different speeds respectively, and alternately bringing substantially the same increments of area of said surface into operative engagement with each of said abrading elements respectively by drivingly rotating said work.

11. The method of finishing a cylindrical surface of apiece of work which comprises the steps of rotatively supportingsaid work, simultaneously applying to circumferentially spaced increments of said surface a pair of reciprocative abrading elements, drivingly reciprocating said elements at respectively different speeds, alternately bringing substantially the same increv ments of area of said surface into operative engagement with each of said abrading elements respectively by drivingly rotating said work, and urging said elements against said work with respectively different pressures. Y

12. The method of finishing a cylindrical surface of a piece of work which comprises the steps of rotatively supporting said work, simultaneously applying to circumferentially spaced increments of said surface a pair of reciprocating abrading elements, drivingly reciprocating said elements at respectively different speeds, alternately bringing substantially the same increments of area of said surface into operative engagement with each of said abrading elements respectively by drivingly rotating said work, and cyclically varying the pressure with which said elements are applied to said work during the finishing operation.

13. The method of finishing a cylindrical surface of a piece of workwhich comprises the steps of rotatively supporting said work, simultaneously applying to circumferentially spaced increments of said surface a pair of reciprocative abrading elements, drivingly reciprocating said elements at respectively different speeds, alternately bringing substantially the same increments of area of said surface into operative engagement with each of said abrading elements respectively by drivingly rotating said work, and cyclically varying the rotative speed of said work during\the finishing operation.

14. Apparatus for finishing a surface of a piece of work including an abrading element, means for supporting said abrading element and work for contacting rotative and reciprocatory movement relative to each other, mechanism for drivingly producing relative rotative and reciprocatory movements of said work and abrading element, and mechanism for urging said abrading element against said work under pressure including a resilient pressure applying element and means operable independently of said first-mentioned mechanism for automatically repeatedly cluding a pair of independently reciprocable finishing abrading elements each engageable with increments of said surface spaced arcuately about the rotative axis of said work, means for drivingly reciprocating each of said elements at respectively different rates, and mechanism for rotating said work during operation of said abrading elements.

16. Finishing apparatus including a frame structure, means thereon for rotatively supporting a piece of work having a surface to be finished, a tool support, a tool on said support including a pair of independently reeiprocable finishing abrading elements each engageable with increments of said surface spaced arcuately about the rotative axis of said work, means for drivingly reciprocating each of said elements throughout respectively different lengths of stroke, and mechanism for rotating said work during operation of said abrading elements.

17. Finishing apparatus including a frame structure, means thereon for rotatlvely supporting a piece of work having a surface to be finished, a tool support, a tool on said support in-' eluding a pair of independently reciprocable finishing abrading elements each engageable with increments of said surface spaced arcuately about the rotative axis of said work, means for drivingly reciprocating each of said elements at respectively difierent rates and throughout respectively different lengths of stroke, and mechanism a for rotating said work during operation of said abrading elements.

18. Finishing apparatus including a frame structure, means thereon for rotatively supporting a piece of work having a surface to be finished, a tool support, a tool shiftably mounted on said support for movement toward and away.-

from said surface including a pair of independently reciprocable abrading elements each engageable with segments of said surface spaced 'arcuately about the rotative axis of said work,

means for yieldably urging said tool toward said work and predetermining the pressure of application of said abrading elements on said surface, mechanism for drivingly reciprocating said abrading elements including a common driving member and drive transmission means operatively connecting the latter with .said abrading elements, said drive transmission means being so constructed and arranged as to establish the reciprocating characteristics of said abrading elements at different predetermined values, and

.means for drivingly rotating said work about said axis.

19. Finishing apparatus including a frame structure, means thereon for rotatively supporting a piece of work having a surface to .be finished, atool support, a tool shiftably mounted on said support for movement toward and away from said surface including a pair of independently reeiprocable abrading elements each en--- gageable with segments of said surface spaced arcuately about the rotative axis of said work, means for yieldably urging said tool toward said work and predetermining the pressure of application of said abrading elements on said surface including mechanism for repeatedly varying the magnitude of said pressure between predetermined limits during a finishing operation, mechanism for drivingly reciprocating said abrading elements including a common driving member and drive transmission means opera.-

tively connecting the latter with said abrading elements, said drive transmission means being so constructed and arranged as to establish the reciprocating characteristics of said abrading elements at different predetermined values, and

aromas tively, mechanism for yieldably urging said elej ments against said surface with respectively different predetermined pressures, and means for drivingly rotating said work during reciprocation of said abrading elements, whereby substantially the same increments of area are brought into operative engagement with each of said abrading elements during a single rotation of said work.

21. Finishing apparatus including a frame structure, means thereon for rotatably supporting a piece of work having a surface tobe finished, a tool support shiftably mounted on said frame structure for feeding movement in the direction of the rotative axis of said work, a pair of tools shiftably mounted on said support for movement toward and away from said surface and arcuately spaced about the rotative axis of said work, each of said tools including a reciproeable abrading element engageable with said surface, means for drivingly reciprocating the abrading elements of said tools and establishing their reciprocating characteristics at differentpredetermined values respectively, mechanism for yieldably urging said elements against said surface with respectively different predetermined pressures, means for drivingly rotating said work during reciprocation of said abrading elements. whereby substantially the same increments of area are brought into operative engagement with each of said abrading elements during a single rotation of said work, and means for shifting said tool support in the direction of the axis of said work to feed said abrading elements over the length of said surface.

22. Apparatus for finishing the surface of a pair of rolls having adjacent cooperating peripheral portions while the latter are supported on their normal bearings of a roll including machine comprising a tool support, a tool mounted on said support including a main body portion and a reclprocative abrading element and means for drivingly reciprocating the latter relative to said main body portion, means for shiftably supporting and adjustably mounting said support in proximity to said rolls; said means and said tool support being spaced laterally from registering portions of said rolls and so constructed and ar.. ranged as to accommodate selective movement of said tool into'unobstructlng relationship with respect to the adjacent peripheral portions of said rolls and into operative engagement with each of said rolls respectively, said tool support and tool being shiftable as a unit in the direction of the axes of said rolls for feeding movements, and means for feeding said tool over the length of said rolls.

"23. Apparatus for finishing the surface of a roll including a frame structure, means thereon for rotatably supporting said roll on its normal axis, a carriage shiftably mounted on said frame structure for reciprocatory movement in the di- 9,195,064 rection of said axis, a plurality of lapping tools shiftably mounted on said carriage in courses substantially converging at said axis, said tools having reciprocatory abrading elements engageable with circumferentially spaced increments of the surface of said roll, means for drivingly reciprocating said elements; rotating said roll and reciprocating said carriage, and fluid pressure mechanism operating upon each of said tools for yieldabiy urging the abrading elements thereof against said surface.

24. The method of finishing a surface havin a multiplicity of minute ridge-like projections thereon to substantially remove said projections and produce a surface substantially free of projections which comprises the steps of: applying an abrading element of predetermined grit size to said surface under a predetermined unit pressure, in the presence of a lubricant coolant of predetermined viscosity, and producing relative movement of predetermined speed between said surface and said abrading element, said predetermined speed, grit size, unit pressure, and viscosity of said coolant being so related that after said projections have been removed and said surface is rendered smooth, a film of said coolant is automatically formed between 'said surface and said abrading element and prevents the grit particles of said abrading element from further cutting into said surface and the grit particles in effect are caused to float upon said surface without scratching or otherwise disfiguring the same. even though said relative movement and application of said pressure continue.

DAVID A. WALLACE.

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