|Publication number||US2836936 A|
|Publication date||Jun 3, 1958|
|Filing date||Nov 13, 1956|
|Priority date||Nov 13, 1956|
|Publication number||US 2836936 A, US 2836936A, US-A-2836936, US2836936 A, US2836936A|
|Inventors||Lovely John W|
|Original Assignee||Bryant Grinder Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (1), Referenced by (13), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 3, 1958 J. w. LOVELY 2,836,936
APPARATUS FOR GENERATING NON-CIRCULAR PROFILES AND SURFACES OF REVOLUTION Filed Nov. 1:5, 1956 4 Sheets-Sheet 1 J y.I /9
i MENTOR John W. Love/y ATTORNEY June 1958 J. w. LOVELY 2,836,936
APPARATUS FOR GENERATIN ON-CIRCULAR PROFILES AND SURFACES REVOLUTION Filed Nov. 13, 1956 4 Sheets-Sheet 2 llllll 3/ INVENTOR John W. Love/y ATTORNEY 2 L I F O R P R w m m Lm .TE
W A m JN ww June 3, 1958 APPARATUS FOR AND Filed Nov. 15, 1
4 Sheets-Sheet 5 INVENTOR J01??? W Lovely BY a%a w AITORNEY June 3, 1958 J. w. LOVELY 2,836,936
APPARATUS FOR GENERATING NON-CIR AR PROFILES AND SURFACES 0F REVOL ION Filed Nov. 13, 1956 4 Sheets-Sheet 4 John W Love/y ATTORNEY INVENTOR United States atent APPARATUS FOR GENERATING NON-CIRCULAR PROFILES AND SURFACES 0F REVOLUTION John W. Lovely, Springfield, Vt., assignor to Bryant Chucking Grinder Company, Springfield, Vt., a corporation of Vermont Application November 13, 1956, Serial No. 621,862
19 Ciaims. (Cl. 51-50) This invention relates to a method and apparatus for generating non-circular profiles or surfaces either externally or internally of a work piece. The invention is specifically illustrated in its application to generating internal non-circular profiles by a grinding operation employing a centerless shoe type grinder.
Prior to this invention, the means for generating noncircular profiles available in the art produced finished pieces that exhibited poor blending between curved and straight portions of the profile and between portions of different radii of curvature. The problem confronted by the art was to obtain stepless blending of the aforementioned portions. This problem, coupled with the requirements of high production rate, usually meant that stepless blending was very difficult as a practical matter. As the production rate increased, the blending became less smooth, and consequently the profile was more inaccurate.
It is a primary object of this invention to provide a method and apparatus for producing non-circular profiles characterized by stepless blending between curved and straight portions and between portions of different radii of curvature.
It is also an object of this invention to provide a method and apparatus for producing stepiess blending even at high production rates.
These and other objects will be apparent from the following description of the accompanying drawings:
Figure 1 is a view in side elevation, partly in section, of a profile grinding machine incorporating work-manipulating improvements in accordance with the principles of the present invention;
Figure 2 is a view in horizontal section of a modified type of work-manipulating equipment according to the present invention;
Figures 3 and 4 are end elevations of the apparatus of Figure 2 in two different positions thereof;
Figure 5 is a View in vertical section of an enlarged scale of the Work-supporting equipment of the assembly of Figure 1;
Figure 6 is a top plan view of the equipment of Figure 5;
Figure 7 is a view similarto Figure 2, but showing an arrangement in which the guiding of the work is partially accomplished by the use of an external surface of the work and showing also a cutting tool in cutting engagement with an end face of the work; and
Figure 8 is a view, likewise similar to Figure 2, but showing an arrangement in which the outside surface of the work is contoured or shaped by work manipulation in accordance with the principles of the present invention.
In prior systems one of the major factors contributing to improper blending and lack of precision of the profile resided in the fact that the necessary oscillatory movement of the work piece was transmitted to said work piece through the movement of the entire headstock. Because of the weight of the headstock, a considerable force was generated upon movement thereof, with deice trimental effect on the exactness of the profile being generated. Consequently, close and precise control of the work piece during profile generation was subject to this force factor, which increased in magnitude with the speed of profile generation. The problem was particularly acute where production rate demands were high.
Referring to Figure 1, the work piece W is shown mounted for horizontal rotation in a cam fixture and work holder 44. The work holder includes a plurality of clamping posts 10 which are slidable axially of the holder and terminate in clamping dogs 11. These dogs engage the work piece and hold it in position for the grinding operation. The grinding wheel 12 is mounted on a rotatable spindle 13. The spindle, in turn, is mounted in a slide 14 which is housed in housing 15. The slide is arranged for rectilinear and reciprocatory movement generally parallel to the axis of the driving spindle for the work piece.
The housing 15 has journaled trunnions (not shown) which engage in bores 16 of lugs 17. These lugs are carried by the upper portion 18 of bed 20 and thereby support the housing in a manner to permit feeding mov ment of the housing along the trunnion axis and transverse to the axis of the spindle driving the work holder. The housing 15 is also supported at 19 in sliding relation to the bed 29. The arrangement of the various elements in this figure are in part disclosed and described in copending application of Maker, Serial No. 578,361, filed April 16, 1956. Sufiice it to say here that with the work piece W properly mounted-in the Work holder and held by the clamping posts 10 for horizontal rotation by the driving spindle (not shown in this figure), the slide 14 carries the grinding Wheel 12 into contact'with the work piece W. The spindle 13 is driven in a conventional manner to rotate the wheel 12 to grind the required profile in the work piece W. The rotation of the work piece W and its specific relaton to wheel 12 at any particular instant during the generation of the required profile is determined by the cam surfaces 45 and 46 and their cam followers or shoes, one of which is indicated at 23. The particular cooperation of cam surfaces and shoes is better illustrated in Figures 2-4, inelusive.
With reference to Figures 2-4, inclusive, there is illustrated the use of a magnetic chuck. This particular type of chuck can be used in connection with the grinder illustrated in Figure 1. The invention here is not limited to the type of chuck. Referring to Figures 24, inclusive, numeral 25 represents the driving spindle for the Work piece. To the face of the spindle 25 is mounted a magnetic material 26. The flux generated by this magnetic material couples the cam fixture 27 to the spindle so that when the spindle rotates, the cam fixture rotates synchronously therewith. However, movement in a vertical plane, that is, in a plane perpendicular to the axis of rotation of the spindle 25 is permitted for the cam fixture. The fixture includes a recess 23 wherein is positioned the work piece W. The work piece W fits against the base 29 of the recess 28 and is coupled thereto by the magnetic flux generated by the magnetic material 26. So as to make sure that there is no relative movement between the cam fixture 27 and the work piece W, dowel pins 30 are provided which engage in cooperating holes in the work piece.
Shoe 31 is shown in engagement with the cam 32. Cam 32 has a circular profile and its center of rotation is indicated by the letter S. Center S also coincides with the point at which the X and Y axes of cam 33 intersect. Cam 33 has a non-circular profile and is the forming cam. Cam 33 is supported by shoe 34, which is approximately displaced from shoe 31. It will be noted, particularly in Figures 3 and 4, that the contacting 2',sse,ase
. 3 7 surface 36 of the shoe 34 is a convex surface. With the center of the driving spindle, indicated at 0, eccentrically offset from said center 8' there is, during rotation of the system, present a resultant force in a direction to establish a stable seating of the cam fixture against the supporting, fixed shoes. Said seating force can be further augmented by suitable pressure. means, or such means can be relied on solely. The operation of this part of the system is disclosed and described in the patent .to Arms et al., 2,635,395, issued April 21, 1953.
The points is actually an arbitrary point. If we describe two lines perpendicularly bisecting both shoes, the intersection of these'two lines is the point R, which is fixed. The point S is taken as a point, common to both cams, which coincides with R at at least one instant during the rotation of the apparatus. In the case where one cam is circular, then S travels along one of the two bisecting lines. In thecase of two non-circular earns, the point S is at any instant of time ata point which is the vector sum of its travel with respect to either of said lines. if, for instance, the travel of S in a direction with respect to one of said lines equals the travel of S in a direction with respect to the other, then the instantaneous position of S is on a line bisecting the angle between the two lines previously described and at avdistance from R'equal to the square root of the sum of the squares of the distance that S traveled with respect to each line.
If we assume now that the task is to generate an internal profile P, which, as is shown, is somewhat in a form approximating that of, an ellipse, it is obvious that an oscillatory movement of the work piece has to be super imposed on its rotative movement provided by the spindle 25. The grinding wheel 12 is, of course, driven by the spindle 13. .zontal diameter ofthe cam 32. The cam 33, the forming cam, has a surface which is determined'by the desired profile to be generated. The art of providing a cam surface to produce a particularly desired profile is well known and is not part of this invention. 'Sufiice it to say that the forming cam 33 has an external profile which is non-circular in a manner to produce the desired internal profile Pin the work surface W. The supporting shoe 34 is positioned so as to contact cam 33 at a point on a horizontal line which is an extension of the horizontal diameter of the tool. The'contacting surface 36 of shoe 34 may be made convex to insure freedom to provide the most favorable co-acting cam profile. The shoe 31 has a contactingsurface 35, which is parallel .to the horizontal diameter of the cam 32 and of such lengthwise extension sufficient to permit an amountvof horizontal travel of cam .32 that is necessary in the generation of. the profile P.
Referringparticularly to Figure 3, 'it will be noted that when the X andY coordinates of cam 33 bear the relation here, there is somedistance between the center of rotation or origins and the center of the tool or grind- "ing'wheel 32. Turning to Figure '4, it will be noted that the distance between S and the center of the tool has been considerably shortened. This shortening takes place during 90 rotation of the work piece and cams, as shown by the 90 rotation of X and Y coordinates. This is due to the fact that the Y coordinate of cam 33 is shorter than the 'X coordinate thereof.
S and the grinding wheel 1-2 would remain constant.
7 However, since one is a forming cam and the other is circular, the distance between point S and thegrinding wheel will vary in a manner which is afunction of the instan:
' taneous X and Y coordinates of the forming caml' 'The vertical relationshipbetween the origin S-and-the grinding wheel 12 remains constant here. That .is be The wheel 12 is positioned on the hori- Therefore, the. instantaneous distance between the tool and point Sis.
cause the cam surface 32 is circular. Additionally, the contacting surface 35 for the shoe 31 is astraight line.
It can be seen, then, that as the cam surface 32 rotates with the other elements, it moves along the contacting surface 35 in a horizontal direction.
The axis of rotation of the spindle 25 is'indicated in Figures 3 and 4 by the letter 0. According to the patent to Arms et al., 2,635,395, supra, the location of the axis of the spindleand the axis of the cam fixture system should be such that the axis of the latter with center S is located in the first quadrant of the former, having center 0. 7
Another embodiment of the inventionhere contemplatesthat the forming cam is actually constituted by the outside profile of the workpiece. This means that only one cam surface has to be provided. on the cam fixture.
Now, turning to Figure 5, we see in detail the type of work holder'which is illustrated in Figure 1. The Work piece W is held in place by the clamping posts 10 and dogs 11. The grinding wheel 12 is shown as being driven by the spindle 13. The spindle for driving the work 'piece'is identified by numeral 38. It will be no? ticed'that this'spindle' is hollow, and within the hollow portion of said spindle is the means for actuating the clamping posts 10. p
The headstock 39, is by a flanged portion 40 supported on the bed 20, and the spindle 38 is arranged for rotative movement in ball bearing assemblies'37. The driving means for the rotative movement is indicated at the lower end of the spindleas a pulley 41 to which power is transmitted by a belt from a motor which is not shown. The upper portion of spindle 38, is an enlargement 42 .terminating in an annular top face 43 supporting the cam fixture 44 in frictional relationship thereto. This cam fixture is substantially identical to the one illustrated in Figures2-4, inclusive. It includes two cams 45 and 46. However, both of these cams are forming cams.
Both have non-circular profiles.
Heretofore, as described with relation to Figures 2-4, inclusive, we have seen that the cam fixture comprised one circular cam and one forming cam. The forming cam compelled the rotating. system to include an oscillatory movement in the horizontal plane while the circular cam held the system to a fixed vertical position with the result that the locus of the origin S was along a horizontal line on which the center of the tool or grinding wheel was also located. By reason of geometry the location of the point of contact between tooland work piece is always on the extension of a line connecting the center of the tool with the center of the instantaneouscurvature of the form generated, said line then being a perpendicular to the tangent of said curvature. The ideal condition would be that said-line is parallel to the direction of the transverse feed movement of the tool. This condition occurs, at best, only in positions of thesystem as shown tations are introduced on the tolerable wear factor or V change'in diameter of the tool. While generating the track form in a pump body, for instance, and using the aforesaid arrangementof one circular cam and one forming cam, certain tests were conducted. It was found that with a change in tool diameter of only .100 inch the said point of contact between tool and work would wander toan extent of approximately 50 from the ideal position, with result that the thus generated profile deviated from the desired true shape a total of .010 inch (from +.005 inch to -.005 inch), In the aforesaidspecial case this was exactly the maximum allowable'tolerance spread of change in shape and'left no safety margin at all. Furthermore, this was only possible at the cost of said economically unsatisfactory wear factor of .100 inch on the tool. To overcome such shortcomings, a second form cam may be substituted for the circular cam, thereby introducing a vertical oscillatory mode in addition to the aforesaid mode of horizontal oscillation of the system. This is the arrangement shown in Figures 5 and 6.
Continuing, then, with Figure 5, we see that the cams 45 and 46 are both forming cams. The cam supports or shoes are carried by a tubular support 47 which is attached to the flanged portion 40. One of the shoes is shown in Figure 5, that is, shoe 48 which supports the cam surface 45. The other shoe 23 is indicated by broken lines in this figure. The cam fixture 44 has two bores which are diametrically spaced in the fixture and receive for, slidable contact therein the clamping posts 10. The bottoms of these posts are provided with shoulders 49 followed by a reduced diameter 50 which fit in holes in a yoke 51 held fixedly therein between the shoulders 49 and a fastening means indicated at 52. Centrally and downwardly protruding from the yoke is fixedly attached one end portion of a universal joint 53. The other end portion of said joint is fixedly attached to one end of a torsion rod 54. The other end of the rod 54, that is, the bottom end thereof, as viewed in this figure, is attached to the first end portion of a second universal joint, indicated by numeral 55. The other end 56 of the universal joint 55 forms a shaft, lengthwise slidable in a bearing bushing 57. This portion 56 is keyed to the bushing 57 to prevent relative torsional movement between the shaft and the bushing. The bushing is fixedly attached to the spindle 38. In the bore 58 of the hollow spindle 38 is a shoulder portion 59. A compression coil spring 60 is positioned with one end bearing against this shoulder 59 and the other end hearing against the washer 61, which is carried by the rod 54 at the top end of the second universal joint 55.
It can be seen that with the system above described, the headstock does not participate in the movement of the work piece. The mass of the elements involved in the movement of the work piece is comparatively small. The spindle rotates the work piece W, and the cooperation between shoes and cam surfaces of the fixture 44 introduces a perpendicularly related oscillatory mode into the movement of the work piece W.
Referring to Figure 6, it will be noted that the contacting surfaces of the shoes 48 and 23 are convex for same reason as above stated for shoe 34.
In Figure 7, the part 62 represents the work-driving spindle, and it corresponds in structure and in function to the parts 25 shown in Figure 2. Magnetically held against the face of the spindle 62 is a cam fixture 63 having an internal cavity in one face for reception of the work W, which in this instance is represented by an annulus. While in Figure 2 the cam fixture includes both of the cams 32 and 33 as portions thereof, in Figure 7 a'cam 64 is contoured on the surface of the cam fixture while another cam 65 is constituted by the external surface of the work itself. The cam supporting shoes 66 and 67 correspond in structure and in function to the parts 31 and 34 of the arrangement of Figure 2, except that the shoe 67 coacts with the external surface of the work itself rather than with the surface provided by the cam fixture. The cutting element 68 of Figure 7 is shown as bearing on an end surface of the work in order to cut a groove or the line therein, the contour of which is controllable by the contour of the earns 64 and 65, as previously described. In Figure 8, the cam fixture rotating member 69 corresponds in structure and function to the part 62 in Figure 7. The cam fixture 70 is in all respects corresponding to the fixture 27 of Figure 2, except that instead of receiving the work internally for internal shaping, the work is dowelled to the end face of the cam 6 fixture so that the external periphery or end face of the work may be shaped.
What have been described are various embodiments of the present invention. Other embodiments obvious from the teachings herein to those skilled in the art are contemplated to be within the spirit and scope of the following claims.
What is claimed is:
l. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, a shaping tool adapted to be placed in working relation to said work piece, axially and circumferentially ofiset, fixed cam supporting shoes, a cam surface coacting with each shoe, at least one of said cam surfaces being on said work holder, and means to rotate said work holder with freedom for limited movement of said workholder normal to the axis of rotation of said means while said cam surfaces are held against said shoes.
2. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, a shaping tool adapted to be placed in working relation to said work piece, axially and circumferentially offset, fixed cam supporting shoes, a cam surface coacting with each shoe, both of said cam surfaces being on said work holder, and means to rotate said work holder with freedom for limited movement of said workholder normal to the axis of the rotation of said means but with said surfaces against said shoes.
3. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, a shaping tool adapted to be placed in working relation to said work piece, axially and circumferentially offset, fixed cam supporting shoes, a cam surface coacting with each shoe, said cam surfaces being on said work holder and means to rotate said work holder with freedom for limited movement of the work holder normal to the axis of the rotation of said means but with said surfaces against said shoes, one of said surfaces being circular but eccentric to the axis of said means.
4. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, a shaping tool adapted to be placed in working relation to said work piece, axially and circumferentially offset, fixed cam supporting shoes, cams coacting with each shoe, both of said cams being on said work holder and means to rotate said work holder with freedom for limited movement of said work holder normal to the axis of the rotation of said means but with said surfaces against said shoes, one of said cams being circular but eccentric to the axis of said means and the other being non-circular, whereby the work is moved normal to the axis of rotation in a path which at every degree of angular displacement represents the vector sum of the distances of a point common to both cams from a coordinate constituting the intersection of the center lines of said shoes.
5. A machine as claimed in claim 4 in which the cam supporting shoe coacting with the circular cam presents an elongated surface tangent to the circular external surface of the respective cam and in which the other of said cam supporting shoes is convex.
6. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, a shaping tool adapted to be placed in working relation to said work piece, axially and circumferentially offset, fixed cam supporting shoes, cams coacting with each shoe, both of said cams being on said work holder and both being non-circular, means to rotate said work holder with freedom for limited movement of the work holder normal to the axis of the rotation of said means, but with said surfaces against said shoes whereby the work is moved in a plane normal to the axis of rotation in a path which represents the vector sum of the instantaneous distances of a point common to both cams from a coordinate constituting the intersection of the center. lines of said shoes.
7. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a hollow work piece in fixed relation thereto, a shaping tool adapted to be placed in working relation to the interior of said work piece, axially and circumferentially offset, fixed cam supporting shoes, a cam surface coacting with each shoe, both of said cam surfaces rotating with said Work holder and means to rotate said work holder with freedom for limited movement of the work holder normal to the axis of rotation ofsaid means but with said surfaces held against the said shoes.
8. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, a shaping tool adapted to be placed in Working relation to the exterior of said work piece, axially and circumferentially offset, fixed cam supporting shoes, a cam surface coacting with each shoe,
both of said cam surfaces rotating with said work holder and means to rotate said work holder with freedom for limited movement of said work holder normal to the axis of rotation of said means but with said surfaces againstthe said shoes.
9. A machine for shaping a surface of a work piece comprising a work holder adapted to hold a work piece in fixed relation thereto, said holder having a first and second peripheral cam surface, said first surface having a non-circular configuratiomsaid second surface having a circular configuration, a first fixed shoe member sup porting said first surface, a second fixed shoe member supporting said second surface, means for rotating said holder whereby said first cam surface and said first fixed shoe member provide oscillatory movement of said work holder in a direction transverse to the rotative movement of said Work holder and said second cam surface and said second fixed shoe member support said work holder in parallel relation to the locus of said oscillatory movement.
10. A machine as defined by claim 9 further comprising a rotatable tool for contacting the surface to be generated, said tool being positioned at a point approximately on a line connecting the point of radial support of said first cam surface by said first fixed shoe member with the origin of rotation of said second cam surface.
11. A machine as defined by claim 10 wherein said first fixed shoe member has a convex supporting face and said second fixed shoe member has a supporting face parallel to said locus of oscillatory movement.
12. A machine as defined by claim 11 wherein the rotative axis of said tool is located on said line.
13. A machine for shaping a surface of a work piece 7 comprising a work holder adaptedto hold a work piece and said second fixed shoe member support. said work holder for movement along a second axis, said second axis being substantially perpendicular to said firstaxis.
14. A machine as defined by claim 13 wherein both of said shoe members have cam'supporting faces of convex configuration.
15. A machine as defined by claim 14 further including a rotatable tool for contacting the surface to be generated,
said tool having a rotative axis positioned at a point approximately on a line perpendicular to the tangent of the instantaneous curvature of the Profile being generated.
16. A machine as defined by claim 15 wherein the axis of said tool and the instantaneous origin of rotation of said work holder are both located on said perpendicular. 17. A machine as definedin claim 16 wherein the point of contact between tool and profile being generated has a locus at the periphery of said tool limited to 15 away from said perpendicular.
18. In a centerless shoe type grinding machine: a workholding'fixture; a rotatable headstock spindle governing the rotational velocity of the workholding fixture whilst an end face of the fixture is axially supported and held in frictional contacting relationship to an end face of the spindle, the perimeter of the fixture providing two,.axially.
curve surfaces, and the other shoe in the same manner supporting the fixture on the other of the closed curve surfaces, whereby, during rotation, a continuous motion 1 of displacement in two radial directions, perpendicular to each other is imparted to the fixture.
19. A machine as claimed in claim 18 further compris- 7 ing a tool adapted to be placed in working relationship to a workpiece fixedly held in the fixture, this working relationship defined asa point where a wall of the workpiece may be interposed in the spacebetween the tool and the contact hetween one of the closed curve surfaces and the 7 shoe cooperating therewith.
References Cited in thefile of this patent UNITED STATES PATENTS 2,592,875 Durland' Apr. 15,1952
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|US3001335 *||Jun 2, 1959||Sep 26, 1961||Bryant Grinder Corp||Apparatus for making a dual diameter ring gage or the like|
|US3663188 *||Jul 20, 1971||May 16, 1972||Tri Ordinate Corp||Cam control grinding machine|
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|US3822618 *||Nov 13, 1972||Jul 9, 1974||Bullard Co||Contour machining|
|US3851422 *||Dec 27, 1972||Dec 3, 1974||Toyo Kogyo Co||Honing machine for finishing trochoidal bore of rotor housing of rotary engine|
|US3914903 *||Aug 24, 1973||Oct 28, 1975||Gleason Works||Apparatus for following a previously shaped surface of a workpiece and for removing stock from such surface without significantly changing the shape thereof|
|US3943665 *||Jul 29, 1974||Mar 16, 1976||Toshiba Kikai Kabushiki Kaisha||Apparatus for profile grinding closed curved surface|
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|US4210039 *||Oct 10, 1978||Jul 1, 1980||Willemin Machines S.A.||Apparatus for forming non-circular workpieces|
|US4221514 *||Jun 23, 1978||Sep 9, 1980||George Fischer Limited||Apparatus for trimming workpieces|
|US4543750 *||Jul 19, 1984||Oct 1, 1985||Leo Froelich||Apparatus for refinishing a pelletizing die|
|USB391437 *||Aug 24, 1973||Jan 28, 1975||Title not available|
|DE2221822A1 *||May 4, 1972||Dec 7, 1972||Tri Ordinate Corp||Vorrichtung zum Schleifen von Flaechen eines Werkstueckes|
|U.S. Classification||451/143, 451/239, 82/18, 409/122|
|International Classification||B24B19/08, B23Q27/00, B24B49/08, B24B19/00|
|Cooperative Classification||B24B49/08, B23Q27/006, B23Q27/00, B24B19/08|
|European Classification||B23Q27/00, B23Q27/00C, B24B19/08, B24B49/08|