Abstract
A circular milling tool for producing a microgroove structure in a cylindrical surface of a bore, the microgroove structure having a groove profile defined by plural microgrooves axially spaced apart and peripherally extend in a circular manner, comprising: a tool base body drivable around an axis of rotation, which carries a circumferential cutter set with first and second circumferential cutters, which are arranged in a row in the circumferential direction, the first circumferential cutter and second circumferential cutter each have a cutting profile that differs from the groove profile of the microgroove structure to be produced, and the circumferentially projected cutting profiles of the circumferential cutters of the circumferential cutter set overlap each other in an axial direction to an extent that they jointly image the defined groove profile of the microgroove structure to be generated. Also, a method for producing a microgroove structure in a bore.
Claims
1. A circular milling tool for producing a microgroove structure in a cylindrical surface of a bore, wherein the microgroove structure has a groove profile that is defined by a plurality of microgrooves that are axially spaced apart and peripherally extend in a circular manner, comprising: a tool base body that can be driven around an axis of rotation, which carries a circumferential cutter set with a first circumferential cutter and a second circumferential cutter, which are arranged in a row in the circumferential direction, the first circumferential cutter and second circumferential cutter each have a cutting profile that differs from the groove profile of the microgroove structure to be produced, and the circumferentially projected cutting profiles of the circumferential cutters of the circumferential cutter set overlap each other in an axial direction to an extent that they jointly image the defined groove profile of the microgroove structure to be generated.
2. The circular milling tool according to claim 1, wherein the first circumferential cutter and the second circumferential cutter each have a cutting profile that has a plurality of cutting teeth in the axial direction.
3. The circular milling tool according to claim 2, wherein the cutting teeth of the first circumferential cutter and/or the second circumferential cutter each have a rectangular tooth profile.
4. The circular milling tool according to claim 2, wherein the cutting teeth of the first circumferential cutter and/or the second circumferential cutter are arranged at the same axial distances.
5. The circular milling tool according to claim 2, wherein the cutting teeth of the first circumferential cutter and/or the second circumferential cutter have the same tooth widths.
6. The circular milling tool according to claim 1, wherein the first circumferential cutter and the second circumferential cutter lie on the same diameter.
7. The circular milling tool according to claim 1, wherein the circumferential cutter set comprises at least two first circumferential cutters and at least two second circumferential cutters, which are alternatingly arranged in the circumferential direction.
8. The circular milling tool according to claim 1, wherein the circumferential cutter set comprises a third circumferential cutter, which has a cutting profile different from the cutting profile of the first circumferential cutter and/or the cutting profile of the second circumferential cutter and/or from the defined groove profile of the microstructure to be produced.
9. The circular milling tool according to claim 8, wherein the third circumferential cutter is arranged between the first circumferential cutter and the second circumferential cutter.
10. The circular milling tool according to claim 8, wherein the third circumferential cutter lies on a smaller diameter than the first circumferential cutter and/or the second circumferential cutter.
11. The circular milling tool according to claim 8, wherein the third circumferential cutter has a single-tooth cutting profile.
12. The circular milling tool according to claim 11, wherein a cutting tooth of the single-tooth cutting profile of the third circumferential cutter has an axial tooth width that is essentially as large as a cutting width of the first circumferential cutter and/or a of the second circumferential cutter.
13. The circular milling tool according to claim 8, wherein the third circumferential cutter has a wavy cutting profile.
14. The circular milling tool according to claim 8, wherein third circumferential cutters set comprises several third circumferential cutters, which each are arranged between one of the first circumferential cutters and one of the second circumferential cutters.
15. The circular milling tool according to claim 14, wherein the circumferential cutter set has a higher number of third circumferential cutters than first circumferential cutters and/or second circumferential cutters.
16. The circular milling tool according to claim 1, wherein the circular milling tool comprises a plurality of axially staggered circumferential cutter sets.
17. The circular milling tool according to claim 16, wherein a respective two axially directly sequential circumferential cutter sets are twisted against each other around the axis of rotation by a predefined angle.
18. The circular milling tool according to claim 17, wherein a respective two axially directly sequential circumferential cutter sets overlap each other in an axial direction.
19. The circular milling tool according to claim 1, wherein the circumferential cutters are each formed on a cutting element indirectly indirectly or directly secured to a tool base body.
20. The circular milling tool according to claim 19, wherein the cutting elements are secured to a side milling cutter carried by the tool base body.
21. The circular milling tool according to claim 1, wherein the circular milling tool comprises a number of chip grooves corresponding to the number of circumferential cutters of the circumferential cutter set.
22. The circular milling tool according to claim 1, wherein the tool base body has a carrier section that carries the circumferential cutter set and a shaft section axially adjoining the carrier section for connecting the circular milling tool with a separating point or interface of a machine tool system.
23. A method for producing a microgroove structure in a bore the microgroove structure comprising a plurality of microgrooves that are axially spaced apart and peripherally extend in a circular manner, and each have a defined groove profile, by means of a rotary driven circular milling tool circulating around an axis of the bore, wherein the bore surface is finished by a 360° circulation of a rotary driven circular milling tool according to claim 1 by virtue of the fact that the cut marks of the circumferential cutters per circumferential cutter set of the circular milling tool that were left behind in the bore surface overlap each other in an axial direction in such a way that they image the defined groove profile of the microgroove structure.
24. The circular milling tool according to claim 1, wherein the circumferential cutter set has a quantity of two first circumferential cutters, which are alternatingly arranged in the circumferential direction.
25. The circular milling tool according to claim 8, wherein the circumferential cutter set comprises four third circumferential cutters, which each are arranged between one of the first circumferential cutters and one of the second circumferential cutters.
Description
[0044] The invention will be described below with the help of drawings. Shown on:
[0045] FIG. 1 is a side view of a circular milling tool according to the invention,
[0046] FIG. 2 is a front view of the circular milling tool,
[0047] FIGS. 3 to 6 are longitudinal section views of the cutting profiles of the circumferential cutters of the circular milling tool,
[0048] FIGS. 7 to 9 are schematic illustrations of cutting teeth of the cutting profiles engaged in an end profile,
[0049] FIG. 10 is a perspective view of the circular milling tool in a first preferred embodiment,
[0050] FIGS. 11 to 13 is a perspective view, a side view, and a front view of the circular milling tool in a second preferred embodiment, and
[0051] FIG. 14 is a perspective view of a cutting element.
[0052] Preferred embodiments of a circular milling tool according to the invention will be described in more detail below with the help of the figures. The figures are only schematic in nature, and serve to provide a better understanding of the invention. Identical elements are labeled with the same reference number. The circular milling tool is conceived for mechanically roughening in a cylindrical surface of a bore in an in particular metallic workpiece, e.g., the piston running surface of a cylinder bore or a cylinder liner in a combustion engine by producing a microgroove structure in the surface. The microgroove structure to be produced here has a defined groove profile, which is defined by a plurality of microgrooves that are axially spaced apart and peripherally extend in a circular manner, so as to achieve a good adhesive base for a surface layer to be applied in particular via thermal spraying. The defined groove profile of the microgroove structure to be produced is referred to as end profile below.
[0053] A circular milling tool 1 according to the invention has a tool base body 10, which can be rotary driven around a longitudinal center line or axis of rotation 2, and can be functionally divided into a shaft section 11 and a carrier section 12. The shaft section 11 can be connected with an interface of a machine tool system (not shown), so as to drive the tool base body 10 around the axis of rotation 2. In the embodiment shown, the shaft section 11 has a hollow shank taper (HST). However, the shaft section 11 can also have a steep taper shank or a cylinder shaft for connecting the circular milling tool 1 with the machine tool system, for example.
[0054] In a preferred first embodiment shown on FIG. 1, the circular milling tool 1 has a modular design. The carrier section 12 carries a plurality of circumferentially cutting cutting tools 20 to 34, which are arranged at defined axial distances from each other on the tool base body 10, and each formed by a side milling cutter in the embodiment depicted. In the embodiment depicted, the carrier section 12 carries fifteen cutting tools 20 to 34, so that a cutting part 13 is designed with a length of 154 mm, for example. The cutting tools 20 to 34 each have the same nominal diameter, e.g., 70 mm, which is less than the inner diameter of the bore to be machined. A clamping screw 14 screwed into the tool base body 10 on the front side clamps the cutting tools 20 to 34 against a shaft-side axial stop formed on the tool base body 10. The clamping screw 14 is designed as a head screw, whose head 15 presses against the foremost cutting tool 20.
[0055] The cutting tools 20 to 34 each have the same structural design. For the sake of simplicity, the structural design of cutting tool 20 will be described below, since the structural design of cutting tools 21 to 34 is similar thereto.
[0056] FIG. 2 shows a front view of the circular miller 1. The cutting tool 20 has a disk-shaped milling base body 35, which carries a plurality of cutting elements 36 arranged in a row in the circumferential direction. Each cutting element 36 has a circumferential cutter 37, wherein the circumferential cutters 37 of the cutting elements 36 form a circumferential cutter set of the cutting tool 20. In the exemplary embodiment shown, the cutting tool 20 has eight cutting elements 36. As a consequence, the circumferential cutter set of the cutting tool 20 has eight circumferential cutters 37, which in the embodiment shown are uniformly distributed over the circumference of the cutting tool 20. The circumferential cutter set of the cutting tool 20 has first circumferential cutters 38, second circumferential cutters 39, and third circumferential cutters 40, which each have a cutting profile that differs from the end profile, in particular corresponds to part of the end profile.
[0057] In the embodiment shown, the circumferential cutter set of the cutting tool 20 has two first circumferential cutters 38, two second circumferential cutters 39, and four third circumferential cutters 40. As evident from FIG. 2, the first circumferential cutters 38 are arranged opposite each other, i.e., offset by 180° in the circumferential direction. The second circumferential cutters 39 are arranged opposite each other, i.e., offset by 180° in the circumferential direction, and between the first circumferential cutters 38, i.e., offset by 90° in the circumferential direction to the first circumferential cutters 38. As a consequence, the first circumferential cutters 38 and second circumferential cutters 39 are arranged so as to regularly alternate in the circumferential direction. The third circumferential cutters 40 are each arranged offset relative to each other by 90° in the circumferential direction, and each arranged between a first circumferential cutter 38 and a second circumferential cutter 39, i.e., offset by 45° in the circumferential direction to a first circumferential cutter 38 and a second circumferential cutter 39. Therefore, the circumferential cutters 37 arranged in a row in the circumferential direction come to be arranged as follows: First circumferential cutter 38, third circumferential cutter 40, second circumferential cutter 39, third circumferential cutter 40, first circumferential cutter 38, third circumferential cutter 40, second circumferential cutter 39, third circumferential cutter 40.
[0058] The first circumferential cutters 38, second circumferential cutters 39 and third circumferential cutters 40 each have a cutting profile that differs both from the end profile and from the cutting profiles of the respective other circumferential cutters 38, 39, 40. The cutting profiles of the first circumferential cutters 38, second circumferential cutters 39 and third circumferential cutters 40 thus leave behind different cut marks in a machined bore surface. Therefore, the cutting profiles of the first circumferential cutters 38, second circumferential cutters 39 and third circumferential cutters 40 engage into the bore surface to be machined in such a way that they each produce only a part of the end profile, i.e., a partial profile, but together yield the complete end profile. This is achieved by virtue of the fact that the cutting profiles of the first circumferential cutters 38, second circumferential cutters 39 and third circumferential cutters 40 projected in the circumferential direction overlap each other according to the invention in such a way or to such an extent in an axial direction and/or in a radial direction as to together image the end profile.
[0059] As a result, the circular milling tool 1 works as follows: If the circular milling tool 1 is driven in the rotational direction, the first, second and third circumferential cutters 38, 39, 40 cut into the bore to be machined one after the other. In this way, each of the first, second and third circumferential cutters 38, 39, 40 remove material, so as to image a part of the end profile. In other words, the first circumferential cutters 38 cut a first cut mark, which is a part of the end profile, i.e., a partial profile, and corresponds to the cutting profile of the first circumferential cutters 38, into the bore surface. The profile surface of the first cut mark is here smaller than the profile surface of the end profile, for example the first cut mark has a groove profile with a smaller groove width. As the circular milling tool 1 continues turning around its axis of rotation 2, the third circumferential cutters 40 cut a third cut mark, which is a partial profile of the end profile and corresponds to the cutting profile of the third circumferential cutters 40, into the bore surface. The third cut mark here differs from the end profile; for example, the third cut mark lies on a smaller diameter around the bore axis than the first cut mark. As the circular milling tool 1 continues to turn around its axis of rotation 2, the second circumferential cutters 39 cut a second cut mark, which is part of the end profile and corresponds to the shape of the cutting profile of the second circumferential cutters 39, into the bore surface. Similarly to the first cut mark, the profile surface of the second cut mark is smaller than the profile surface of the end profile; for example, the second cut mark has a groove profile with a smaller groove width than the end profile, but deviates from the first cut mark; for example, the second cut mark has a groove profile with the same groove width as the first cut mark, but is axially offset. In the preferred embodiment, the first and second cut mark overlap each other in the axial direction for the most part, for example by more than 80% of the respective groove width.
[0060] FIG. 3 shows a cutting element 36 that forms the first circumferential cutters 38. The cutting profile of the first circumferential cutter 38 has a plurality of cutting teeth 38a, which are spaced apart from each other at identical axial tooth distances and each have the same tooth width and tooth height. The cutting teeth 38a thus have a constant axial pitch. In the embodiment shown, the cutting teeth 38a of the first circumferential cutter 38 each have a rectangular profile. The tooth width B.sub.38a is measured as the distance between a front tooth flank 38b (in an axial infeed direction of the circular milling tool) and a rear tooth flank 38c (in the axial infeed direction of the circular milling tool) of a cutting tooth 38a. The tooth height H.sub.38a is measured as the distance between a tooth base 38d and a tooth tip 38e. Each tooth base 38d of the cutting teeth 38a lies on a constant tooth base diameter D.sub.38d. Each tooth tip 38e of the cutting teeth 38a lies on a constant tooth tip diameter D38e, which also comprises the diameter D.sub.38 of the first circumferential cutter 38. The axial tooth distance A.sub.38a is here measured as the distance between the rear tooth flank 38c of a cutting tooth 38a and a front tooth flank 38b of a cutting tooth 38a that is adjacent thereto and arranged behind it in the axial infeed direction of the circular milling tool 1. The axial pitch T.sub.38a at which the cutting teeth 38a are arranged is measured as the distance between the front tooth flanks 38b of a respective two cutting teeth 38a adjacent in the axial direction. Therefore, the axial pitch T.sub.38a corresponds to the sum of the axial tooth distance A.sub.38a and the tooth width B.sub.38a. Each first circumferential cutter 38 has an overall width B.sub.38.
[0061] FIGS. 4a and 4b show two variants of a cutting element 36, which comprises one of the second circumferential cutters 39. The cutting profile of each second circumferential cutter 39 has a plurality of cutting teeth 39a, which are arranged spaced apart at identical axial tooth distances from each other, and each have the same tooth width and tooth height. The cutting teeth 39a thus have a constant axial pitch. In the embodiment shown, the cutting teeth 39a of the second circumferential cutters 39 each have a rectangular profile. The tooth width B.sub.39a is measured as the distance between a front tooth flank 39b (in the infeed direction of the circular milling tool) and a rear tooth flank 39c (in the infeed direction of the circular milling tool) of a cutting tooth 39a. The tooth height H.sub.39a is measured as the distance between a tooth base 39d and a tooth tip 39e. Each tooth base 39d of the cutting teeth 39a lies on a constant tooth base diameter D.sub.39d. Each tooth tip 39e of the cutting teeth 39a lies on a constant tooth tip diameter D.sub.39e, which also comprises the diameter D.sub.39 of the second circumferential cutter 39. The axial tooth distance A.sub.39a is measured as the distance between a rear tooth flank 39c of a cutting tooth 39a and a front tooth flank 39b of a cutting tooth 39a that is adjacent thereto and arranged behind it in the axial infeed direction of the circular milling tool 1. The axial pitch T.sub.39a at which the cutting teeth 39a are arranged is measured as the distance between the front tooth flanks 39b of a respective two cutting teeth 39a adjacent in the axial direction. Therefore, the axial pitch T.sub.39a corresponds to the sum of the axial tooth distance A.sub.39a and the tooth width B.sub.39a. Each first circumferential cutter 39 has an overall width B.sub.39.
[0062] In the embodiment shown, the cutting profile of a first circumferential cutter 38 (see FIG. 3) corresponds to the cutting profile of a second circumferential cutter 39 (see FIGS. 4a and 4b) with regard to the axial pitch of the cutting teeth 38a or 39a (T.sub.38a=T.sub.39a), the axial tooth distance of the cutting teeth 38a or 39a (A.sub.38a=A.sub.39a), the tooth width of the cutting teeth 38a or 39a (B.sub.38a=B.sub.39a), the tooth height of the cutting teeth 38a or 39a (H.sub.38a=H.sub.39a), the tooth base diameter (D.sub.38d=D.sub.39d), the tooth tip diameter (D.sub.38e=D.sub.39e), the diameter of the circumferential cutters 38 or 39 (D.sub.38=D.sub.39) as well as the overall width of the circumferential cutter 38 or 39 (B.sub.38=B.sub.39). The cutting profile of a circumferential cutter 39 shown on FIG. 4a differs from the cutting profile of the circumferential cutter 38 shown on FIG. 3 in that the cutting teeth 39a are arranged around an offset V axially offset relative to the cutting teeth 38a, but the second circumferential cutter 39 is axially arranged at the same height as the first circumferential cutter 38. The cutting profile of a circumferential cutter 39 shown on FIG. 4b has the same cutting profile as a circumferential cutter 38 shown on FIG. 3, but the second circumferential cutter 39 shown on FIG. 4b is arranged around the offset V axially offset relative to the first circumferential cutter 38. To provide a better understanding, the offset V in the embodiment depicted is not to scale, but rather magnified.
[0063] The variants shown on FIGS. 4a and 4b are now possible for producing a different groove profile in a bore surface: (1) The circumferential cutters 38 and 39 are arranged at the same height in an axial direction, while the cutting teeth 38a of the circumferential cutter 39 are axially offset relative to the cutting teeth 38a of the circumferential cutter 38 by offset V, as shown on FIG. 4a, or (2) the identically designed second circumferential cutters 38 and 39 are axially offset relative to each other by offset V, as shown on FIG. 4b.
[0064] FIG. 5 shows a cutting element 36, which comprises one of the third circumferential cutters 40. The cutting profile of every third circumferential cutter 40 has a single-tooth design. In the embodiment shown, the one cutting tooth 40a of every third circumferential cutter 40 has a wavy profile, as depicted on FIG. 5. The third circumferential cutter 40 has an overall width B.sub.40. The cutting profile of the third circumferential cutter 40 is configured so as to machine the webs S between the grooves of the end profile of a machined bore surface to a predefined diameter D.sub.R. The third circumferential cutters 40 thus lie on a smaller diameter D.sub.40 than the first circumferential cutters 38 (D.sub.38>D.sub.40) and the second circumferential cutters (D.sub.39>D.sub.40). However, the diameter D.sub.40 of the third circumferential cutters 40 is greater than the tooth base diameter D.sub.38d of the first circumferential cutters 38 (D.sub.38d<D.sub.40) and the tooth base diameter D.sub.39d of the second circumferential cutters 39 (D.sub.39d<D.sub.40)
[0065] FIG. 6 shows the end profile, which results from overlapping the cut marks left behind in a machined bore surface or partial profiles of the circumferential cutters 38, 39 and 40 of a circumferential cutter set. The end profile has a plurality of microgrooves, which each have the same groove width B.sub.R and groove depth H.sub.R. The webs S are arranged between adjacent microgrooves, and each have the same web width B.sub.S. As a result, the microgrooves have a constant axial pitch T.sub.R. The groove width B.sub.R is measured as the distance between a front groove flank VRF and a rear groove flank HRF of a microgroove. The groove depth H.sub.R is measured as the distance between a groove base RG and a web tip SS. The web width B.sub.S is measured as the distance between a rear groove flank HRF of a microgroove and a front groove flank VRF of a microgroove adjacent thereto and arranged behind it in the axial infeed direction of the circular milling tool. The axial pitch T.sub.R at which the microgrooves are arranged is measured as the distance between the front groove flanks VRF of two respective microgrooves adjacent in an axial direction. The web tips SS lie on a diameter that comprises the inner diameter D.sub.R of the microgrooves. The microgrooves of the end profile have a groove width B.sub.R and a groove depth H.sub.R. The groove width B.sub.R is greater than the tooth width B.sub.38a or B.sub.39a (B.sub.R>B.sub.38a, B.sub.R>B.sub.39a) the groove depth H.sub.R is less than the tooth height H.sub.38a or H.sub.39a (H.sub.R<H.sub.38a, H.sub.R<H.sub.39a) the axial pitch T.sub.R corresponds to the axial pitch T.sub.38 or T.sub.39 (T.sub.R=T.sub.38, T.sub.R=T.sub.39) and the diameter D.sub.R of the end profile is less than the diameter D.sub.38 or D.sub.39 (D.sub.R<D.sub.38, D.sub.R<D.sub.39) , equal to the diameter D.sub.40 (D.sub.R=D.sub.40), and greater than the tooth base diameter D.sub.38d or D.sub.39d (D.sub.R<D.sub.38d, D.sub.R>D.sub.39d).
[0066] FIGS. 7 to 9 schematically depict a cutout of the end profile of the machined bore surface and the engagement of the first, second or third circumferential cutters 38, 39, 40 into the end profile. The first circumferential cutter 38 machines the rear groove flanks HRF of the end profile with its rear tooth flanks 38c of the cutting teeth 38a, while the second circumferential cutter 39 machines the front groove flanks VRF of the end profile with its front tooth flanks 39b of the cutting teeth 39a. The groove base RG of the end profile is machined by the tooth tips 38d, 39d of the first or second circumferential cutter 38, 39. The third circumferential cutter 40 machines the webs S, and thus the diameter D.sub.R of the end profile.
[0067] FIGS. 7 and 8 show that, as already mentioned, the tooth widths B.sub.38a, B.sub.39a of the cutting teeth 38a, 39a of the first and second circumferential cutters 38, 39 are smaller than the groove width BR between the front groove flank VRF and rear groove flank HRF. FIG. 9 shows that, as already mentioned, the webs S between the microgrooves of the end profile are brought to the diameter D.sub.R by the third circumferential cutters 40. As a consequence, the chipping load for producing the end profile is distributed to the first, second and third circumferential cutters 38, 39, 40, which each only produce a part of the end profile.
[0068] FIG. 10 shows a perspective view of the first preferred embodiment of the circular milling tool 1. The cutting tools 20 to 34 are force-locked to the tool base body 10. Modeled after the circular milling tool indicated in DE 10 2016 216 464 A1, the cutting tools 20 to 34 receive the peg-like carrier section 12 with their respective center recess. The cutting tools 20 to 34 are non-rotatably fixed relative to the tool base body 10 in the circumferential direction by means of a tappet, for example a feather key. The cutting tools 20 to 34 are twisted relative to each other, so that the first, second and third circumferential cutters 38, 39, 40 each run along helical lines or coils. What this means is that a respective two axially directly sequential circumferential cutter sets are twisted relative to each other by a predefined angle. The first circumferential cutters 38 or second circumferential cutters 39 or third circumferential cutters 40 of two axially sequentially arranged cutting tools are arranged one after the other in the circumferential direction or rotational direction, so that they cut into the cylindrical surface to be machined in a time-displaced manner. This results in coiled chip grooves 16, the number of which corresponds to the number of circumferential cutters 37 per circumferential cutter set. In the exemplary embodiment shown, eight chip grooves 16 are formed. Viewed as a whole, the cutting part 13 of the circular milling tool 1 is helically grooved in design. The circumferential cutters 37 of two respective axially directly sequential circumferential cutter sets overlap each other in the axial direction. In the embodiment shown on FIG. 10, the circumferential cutters 37 are each indirectly secured to the tool base body 10 via the cutting tools 20 to 34.
[0069] FIGS. 11 to 13 show a second preferred embodiment of the circular milling tool 1 according to the invention. The second preferred embodiment essentially corresponds to the first preferred embodiment. For this reason, only the differences will be described below. The circumferential cutters 37 are each formed on a cutting element 50, and the cutting elements 50 are individually secured to a carrier section 12 of the tool base body 10. As opposed to the first embodiment, the circumferential cutters 37 are not indirectly fixed by a respective cutting tool 20 to 34, but directly fixed to the tool base body 10. To this end, each cutting element 50 is arranged in a pocketlike recess on the carrier section 12 of the tool base body 10, and screwed to the carrier section 12. Several cutting elements 50 axially arranged at the same height and distributed uniformly over the circumference comprise a circumferential cutter set. The circumferential cutter set has the first circumferential cutters 38 described above and second circumferential cutters 39 described above. The circumferential cutter set can also have third circumferential cutters 40 described above.
[0070] As shown on FIG. 14, the cutting elements 50 are formed in two parts, and have a carrier 50a and a cutting body 50b fastened thereto, e.g., soldered or adhesively bonded. For example, the cutting body 50b can be made out of PKD, CBN or a comparable hard material, while the carrier body 50a can be made out of solid carbide, steel, or the like, for example.
