AT514119A1 - Cutting part for a drill - Google Patents

Abstract

A cutting part (1) for drilling into a ceramic member is plate-shaped, can be inserted into an insertion slot (21) of a shaft (20) and has at least a main cutting area (14) with a main cutting edge (2) and a tip (5) with a transverse cutting edge (3). on. The cutting part (1) defines a longitudinal axis (L), a major axis (H) and a transverse axis (Q) perpendicular to each other and passing through the geometric center of gravity of the main cutting area (14). The transverse cutting edge (3) is formed by blending two tip surfaces (6, 7) and the ends of the transverse cutting edge (3) are defined by two spotting surfaces (8, 9) which, together with the tip surfaces (6, 7), respectively form a first tip main cutting edge (11) and forming a second tip main sheath (13). The center (5) of the transverse cutting edge (3) is offset from the longitudinal axis (L) by an eccentricity measure (e) of at least 1% of the nominal diameter of the cutting part (1) in the direction of the transverse axis (Q), so that the first peak main cutting edge (11) shorter than the second tip main cutting edge (13).

Description

10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 From © 5 of 24 ·· · > ·: ·· ·· ···· • ·: · · # · '·' ·· · · • Φ «. * * 9 '' ······················································ AT 69175

CUTTING PART FOR A DRILL

The present invention relates to a cutting part for a drill for drilling in a ceramic component, such as a fine

Known from the prior art drills, which can be used for both glass and porcelain stoneware. Typically, such drills consist of a shank 20 '(see FIG. 3) having at its front end an insert 21' into which a plate-shaped cutting member 1 'made of hard metal (see FIG. 4) is inserted and soldered to the shank 20' is. The cutting part 1 'shown in FIG. 4 has a flame-shaped main cutting area, the main cutting edges 2' of which run toward one another towards a point 5 'and terminate in a transverse cutting edge 3'. The transverse cutting edge 3 'results from the course of the free surfaces of the main cutting edges 2' and its center lies on the longitudinal axis of the sheath part 1 '.

In particular, the processing of hard, ceramic tiles is becoming increasingly important. On the one hand the offer of ceramic tiles gets bigger, on the other hand the tiles get harder (up to Mohs 9), they are relatively cheap and they are wear-resistant.

The known from the prior art, equipped with carbide cutting parts bits wear out quickly and it can only a limited number of holes, experience one to a maximum of two holes are made with a drill. A well-known alternative is diamond drilling tools, which, however, can only be used refrigerated and are relatively quickly destroyed in untrained use. P.005 / 024 10/04/2013 15:08 2/25 R887 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: »64173 Page 6 of 24 • · · ··· · ·: · · · • · · «I · · 4 · ·. ♦ • · · · · · · · · 4 "* *" "··" * ♦ «♦ 02/13 AT 69175

In addition, the flame-shaped edge tends to break because of uneven tensile and compressive stresses along the flame shape, and the wide transverse cutting edge wears relatively fast over the entire plate thickness, since the drilling dust can not be optimally promoted, wear is primarily due to non-promoted drill dust, which leads to excessive heat.

It is therefore the object of the present invention to provide a drill which is particularly resistant to wear when drilling fine Feinzezinze and therefore allows the drilling of significantly more holes with only one drill.

Erfindüngsgemäß this object is achieved with a cutting part for drilling in a ceramic component, wherein the cutting part is plate-shaped, can be inserted into an insertion slot of a shaft and at least one main cutting area with a main cutting edge and a tip with a cross-cutting edge, wherein the cutting part has a longitudinal axis, defining a major axis and a transverse axis perpendicular to each other and passing through the geometric center of gravity of the main cutting region, the transverse cutting edge being formed by cutting two tip surfaces, and the ends of the transverse cutting edge being defined by two cutting surfaces which, together with the tip surfaces, respectively Main cutting tip and form a second tip main sheath, wherein the center of the transverse cutting edge is offset from the longitudinal axis by a Auszentrizitätsmaß of at least 1% of the nominal diameter of the cutting part in the direction of the transverse axis, so d The first tip main cutting edge is shorter than the second tip main cutting edge. P.006 / 024 10/04/2013 15:08 / 25rq87 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: £ 64173 «· 9 9 9 * 99 ·

• «9 · 999 9 9 'I ···' .. ·. · 9 *. ·: ..... · 3/13 AT 69175

In this cutting part, the center of the transverse cutting edge, when the cutting part is inserted into the insertion slot of the shaft and connected thereto, with a corresponding exact alignment of the longitudinal axis of the blade on the longitudinal axis of the shaft from the longitudinal axis of the shaft by an eccentricity of at least 1% of Nominal diameter of the cutting part offset in the direction of the transverse axis.

During operation of the drill, the eccentric cross-cut creates a kind of stirring movement at the drill tip. The first and shorter tip main cutting thereby generates a tumbling motion and thus ensures the Bohrvortrieb. The second, longer main cutting edge supports and promotes the detached Bohrraehl from the borehole. This leads to less overheating and allows longer drill life.

Through experiments, this operation was confirmed, as appropriate wear was observed on the shorter tip main cutting edge of the drill bit.

Preferably, one end of the transverse cutting edge lies on the longitudinal axis. In other words, the ends of the transverse cutting edge are displaced along the transverse axis about the center offset of the Ausspitzungsflächen. One end of the transverse hinge thus lies around the difference of half the transverse cutting width to the center offset of the Ausspitzungsflächen on the longitudinal axis.

Preferably, the measure of eccentricity is greater than 1.5%, 2%, 3%, 4% or 5% of the nominal diameter of the cutting part. The larger the amount of eccentricity, the shorter the first main cutting edge becomes, and the longer the second main cutting edge becomes, so that the wobbling motion through the first cutting edge will be 10/04/2013 15:09 | 4/25 R887 P. 0077024 10.04.2013 Wed 15: 07 TBK +49 89 54469290 ID: # 64173 Page 8 of 24 {«« »9 9 9 99 9 • 9 · · 9999 9 9 •« • 9 99 99 99 9 99 9 9 9999 99 99 99 4/13 AT 69115 zen main cutting edge and the supporting and discharging by the second tip main cutting edge is generated more clearly.

Preferably, the tip surfaces define a point angle greater than 90 °. Further preferably, the tip angle is 100 °. This point angle corresponds to 116 to 120 ° in the front view of the ground drill.

Preferably, the peaking surfaces define a cut-off angle that is less than 90 °. Further preferably, the AusSpitzungswinkel is 60 °.

Preferably, wherein an edge defined by the intersection of the longer second second major cutting edge forming surface with a side surface of the cutting member defines an angle with the major axis and the transverse axis at an angle ranging from 5 ° to 25 °. Further, this angle is preferably 15 °. By virtue of this measure, a space which lies in the direction of movement of the cutting part in front of the second tip main cutting edge is opened further by a larger opening between the edge and the bore wall. Therefore, accumulating debris can be better transported away.

Preferably, the main cutting area has two cylinder cutting edges at the end opposite the tip and two cone cutting edges between the tip and the cylinder cutting edges, wherein the cone cutting edges and the cylinder cutting edges are rectilinear. Further preferably, the angle between the conical blades is about 30 °.

In essence, it turned out that the cone-like shape of the plate at the tapered blades at an angle in the range 10/04/2013 15:07 | 5/25 R887 P.008 / 024 10.04.2013 Μι 15:07 TBK +49 89 54469290 ID: # 64173 Page 9 of 24 • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·· * 5/13 AT 69175 from 30 ° to 36 ° between them is optimal. For example, tungsten carbide plates with flame shape can be re-ground for this purpose. The inventive point sharpening by the tip surfaces and the Ausspitzungsflächen with eccentric offset of the transverse cutting edge ensures rapid penetration, for example, in the tile and the enlarging cone rubs the hole with little effort. As a result, in contrast to the flame shape, only minimal breakouts occur on the boring side and, as a consequence, tile breakage can be avoided.

Preferably, the cutting part is made of hard metal.

Furthermore, a drill according to the invention has a shank and a cutting part according to the above features, which is inserted into and connected to an insertion slot at the front end of the shank. Further preferably, the cutting part is soldered in Einsetzseh1itz.

Preferably, the diameter of a clamping slot of the shaft opposite the insertion slot is greater than the nominal diameter of the blade part. This makes it possible to transmit the large torques required by the eccentricity of the cross cutting edge.

Preferably, the clamping portion of the shaft opposite the insertion slot has one or more clamping surfaces. As a result, even larger torques can advantageously be transmitted.

Preferably, the clamping section is provided with one or more SDS grooves and / or the clamping surfaces are designed according to DIN 3126. 10/04/2013 15:10 6/25 R887 P.009 / 024 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 Page 10 of 24 * · · · · * * · · «« · · · * · · · · • · '· · · · · · · · • * Ü * t * «« «· AT 69175

A method according to the invention for producing a cutting part according to the above features comprises providing a green sheet defining a longitudinal axis, a major axis and a transverse axis perpendicular to each other and passing through the geometrical center of gravity of the green sheet, inserting two major cutting edges in the direction of Main axis of opposite sides of the raw plate, wherein the main cutting edges approach each other in the direction of the longitudinal axis, the introduction of two tip surfaces through the cut a transverse cutting edge is formed, and the introduction of two Ausspitzungsflächen, which are defined by the end of the cross cutting edge and together with forming the tip surfaces respectively a first tip main cutting edge and a second tip main cutting edge, wherein the two tapering surfaces are inserted such that the center of the transverse cutting edge is spaced from the longitudinal axis by an eccentricity amount of at least 1% of the nominal diameter of the blade part is offset in the direction of the transverse axis, so that the first tip main cutting edge is shorter than the second tip main cutting edge.

With this method, the cutting part can be precisely produced.

Advantageously, the Ausspitzüngsflächen and the tip surfaces are caused by grinding with the end face of a cup wheel with process-dependent angle of attack. As a result, particularly flat Ausspitzüngsflächen and tip surfaces and thus precise cutting edges can be generated.

Preferably, the green sheet has a curved main cutting edge, and the method comprises the step of grinding the curved main cutting edge into a straight major cutting edge. 10/04/2013 15:10 17/25 (1887 P.010 / 024 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 Page 11 of 24 9 ·· · · · · · · · · · · •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• · • «ft • · 99 7/13 AT 69175

Preferably, in the method, all machining except the creation of the Ausspitzungsflächen done centrally to the tool longitudinal axis, wherein the Ausspitzungsflachen are offset by a measure of eccentricity to the longitudinal axis. The center distance of the relief surfaces is given along the transverse axis and should be at least 1 l of the nominal thickness of the cutting part. As a result, the center of the transverse cutting edge also shifts by the center offset of the

Now, an embodiment of the invention will be explained with reference to the accompanying drawings. In the figures is

1A is a side view of a cutting part according to the embodiment in the transverse direction,

1B is a plan view of the cutting part of FIG. 1,

FIG. 1C is a section along the line A-A of FIG. 1, FIG.

Fig. 1D is a section taken along the line B-B of Fig. 1

FIG. 1 IE shows a side view of the cutting part from FIG. 1 in main direction, FIG.

1F is an enlarged plan view of the area C of FIG. IE,

2A is a side view of a shaft for mounting the cutting part of Figures 1A to 1 F, 10/04/2013 15:11 8/25 No .: R887 P.011 / 024 10.04.2013 Wed 15: 07_TBK +49 89 54469290 ID: # 64173 Page 12 of 24 ······················ · · ♦ · · · • · · · "· · · · · · · · · · · · #" · "". 8/13 AT 69175

2B is a side view in the main direction of the blade mounted on the cutting part,

2C shows a lateral view in the transverse direction of the shaft-mounted part of the blade,

3 shows a shaft according to the prior art,

4 shows a cutting part according to the prior art,

Best way to carry out the invention

1A shows a side view of a plate-shaped cutting part 1 according to the invention seen in the transverse direction, ie in the direction of the transverse axis shown in FIG. 1B. The cutting part 1 has a main cutting portion 14, in each of which a cone cutting edge 2 and a cylinder cutting edge 4 are provided on opposite sides of the plate-shaped cutting part 1 in the main direction. At the end of the conical cutting edge 2 opposite the cylinder cutting edge 4, the cutting part 1 has a tip 5 with a prismatic grinding surface consisting of two tip surfaces 6, 7 and two tipping surfaces 8, 9 which define a transverse cutting edge 3, a first tip main cutting edge 11 and a second tip main cutting edge 13 (see Fig. 1F).

The conical blade 2 shown in Fig. 1A is rectilinear and forms on the narrow side of the plate-shaped cutting part 1, a free surface 15 which forms a clearance angle γ with the transverse axis Q (see Fig. 1B), which in the section shown in Fig. IC, for example 15 ° (γΐ) and in the section shown in Fig. ID, for example, can be 14 ° (γ2). The free surfaces 15 as well as the tip surfaces 6, 7 may have a key. P .012 / 024 10/04/2013 15: 1 1 | 9 / 25R887 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 Page 13 of 24 4 4 9 · · ·········································································································································································································································· they can be multi-faceted.

For the purpose of definition, it is assumed that the main cutting portion 14 of the cutting part 1 is formed substantially symmetrical to the longitudinal axis L. Based on this assumption, the major axis H and the transverse axis Q are defined which are perpendicular to each other and both intersect the longitudinal axis L.

On the basis of this axis definition, the geometric relationship of the main cutting edges 2, the free surfaces 15, the transverse cutting edge 3, the tip surfaces 6, 7 and the Ausspit-zungsflächen 8, 9 is described, in this embodiment, these surfaces in the cutting part shown in Fig. 4 1 'are introduced.

First, the curved main cutting edges 2 'are ground in compliance with the angles γΐ and γ2 shown in Figures IC and ID, so that the cone cutting edge 2 in each case with an angle δ of 15 ° results, so that the two cone cutting edges together an angle of about 30 ° include.

Subsequently, the tip surfaces 6, 7 are introduced so that they include a point angle of 100 ° and form between them a transverse cutting edge 3, which in the detail shown in Fig. 1F with respect to the transverse axis Q is inclined by about 20 °. The inclination of the transverse cutting edge 3 can hang together with the clearance angle γ of the main cutting edge 2. However, the transverse cutting edge 3 can also run parallel to the transverse axis Q. 10/04/2013 15:12 10! 2-¾ 8 7 P.013 / 024 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 Page 14 of 24 · '· ·. ·. · ≫ English:. German: v3.espacenet.com/textdoc? / 13 AT 69175

Then the Ausspitzungsflächen 8, 9 are introduced, which determine the position of the end point of the transverse cutting edge 3. In addition, the first tip main cutting edge 11 and the second tip main cutting edge 13 are formed by the intersection of these Ausspitzungsflächen 9, 9 respectively with the Ausspitzungsflächen 6, 7. The AusspitzUngsflachen 8, 9 are introduced so that the transverse cutting edge 3 at its in Fig. 1F right End stronger than at the left end is shortened. In Fig. 1F, the right end is almost on the longitudinal axis L, whereas the left end is clearly offset from the longitudinal axis in the transverse direction. This results in that the center of the transverse cutting edge 3 is offset by an eccentricity e from the longitudinal axis L in the direction of the transverse axis. For a drill with a nominal diameter of 8 mm, the eccentricity measure e is at least 0.08 mm, ie 1% of the nominal diameter. Tests have shown that drills with an eccentricity measure e up to approx. 0.3 mm, ie approx. 3.75% of the nominal diameter, have achieved good results, ie made more than 20 holes possible per drill, before the drilling effect clearly decreased as a result of wear.

In this regard, further, it should be noted that because of the eccentricity of the cross cutter 3 to the left in Fig. 1F, the first tip main cutting edge 11 becomes shorter and the second tip main cutting edge 13 becomes longer. Further, a larger portion of the chisel edge 3, if not the entire chisel edge 3, is located in the area of the point advancing in the counterclockwise direction.

As a result, the shorter first tip main cutting edge 11 generates a wobbling motion and thus provides the drilling advance. The longer second main cutting edge, on the other hand, supports and conveys the detached drilling dust out of the borehole. Due to the removal of the drilling dust, less friction occurs and therefore less 15/02/2013. /.--?I887 P.014 / 024 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 Page 15 of 24 • · '' • • • • • • • • • • • • • t 1 · • ·, * · ··· * 11/13

• * AT 69175 overheating, so extended drill life can be achieved. This operation can also be confirmed by the wear of the drill bit, since after the tests the shorter "cutting " Tip main cutting edge 11 more worn than the longer "promotional " Peak head cutting edge 13 was.

Furthermore, it can be seen from FIG. 1A that the Ausspitzungsfläche 8 is formed such that the edge 16 at the waste of the Aususspitzungsfläche 8 with the side surface of the cutting part 1 in the main cutting area 14 with the main axis H defines an angle, for example, of 159. This angle results from the clearance angle of the outer surface 8 with respect to the main cutting edge 13 and causes the edge 16 does not intersect with the edge 17 between the free surface 14 and the top surface 7, but that here the edge 16 with respect to the edge 17 from the top 15 way is offset.

When cutting into the ceramic material, a frusto-conical hole is created by the chisel edge 3 and the tip main cutting edge 11, which rotate about the longitudinal axis L, the transverse cutting edge 3 and the Spitzenhauptschneid® H act as a generator. This can be seen particularly clearly in FIG. IE, which shows the transverse cutting edge 3 and the first tip main chords 11 in a view in which they are perceived as generatrix. In this case, the first tip main cutting edge 11 begins only at the radially outer ends of the transverse cutting edge 3 and only there reduces the radial dimension of the tip 5. In contrast, the second tip main cutting edge 13 begins much closer to the longitudinal axis L and therefore reduces the radial dimension of the tip 5 with With respect to the longitudinal direction of the cutting part 1 earlier. Consequently, at the points in the borehole where the second top 10/04/2013 15:13 12/25 No .: R887 P.015 / 024 TBK +49 89 54469290 10.04.2013 Wed 15:07 ID: 464173 Page 16 of 24 ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• AT 69175 main cutting edge 13 comes past, the material already scraped by the first SpitzenhauptSGhneide 11, so that the second main cutting edge 13 essentially does no more Schabarbeit but only transported the drilling dust.

In a conventional tip without eccentricity also the space between the tip main cutting edges is almost closed and only through a small gap between the truncated cone shaped borehole wall and the edges 18 and 19 in Fig. 1B corresponding edges open. Therefore, the drilling dust can be removed badly.

On the other hand, in the cutting part according to the invention, the space in the borehole formed in the moving direction in front of the first tip main cutting edge 11 and behind the second tip main cutting edge 13 is connected to the space in the direction of movement in front of the second tip main cutting edge 13 through the gap between the borehole wall and the second tip main cutting edge 13; Therefore, the lohr meal accumulating on the first tip main cutting edge 11 can be transported away from the second tip main cutting edge 13 in the space in the direction of movement by the gap between the borehole wall and the second tip main cutting edge 13.

In addition, since the edge 16 is inclined, the space in the direction of movement in front of the second tip main cutting edge 13 is further opened by larger openings between the edge 16 and the borehole wall, so that the drilling dust can be effectively discharged into the main cutting region 14.

In this embodiment, the flame-shaped cutting part 2 'shown in Fig. 4 has been modified. However, it is also possible to use a raw plate, which is already straight 10/04/2013 15:13 l 8: 7 'P.016 / 024 10.04.2013 Μι 15:07 TBK +49 89 54469290! D: # 64173 Page 17 of Has main cutting edges, or straight main cutting edges without a detour via flame - shaped main cutting edges into one To bring raw board.

The cutting part 1 according to the embodiment is by 1) Production step: drill blank with soldered carbide plate

Extruded parts or blanks made of bar stock are used. These are automatically slit on a production line and the cutting part is inserted. Subsequently, the drills are annealed and soldered in a vacuum furnace, so that a permanent connection with the cutting part is created. 2) Production step: lace grinding

The drills are ground on a CNC tool-sharpening machine with a cup wheel on the plan side of the grinding wheel with pre-pushing motion on the contour and a defined angle of attack. P.017 / 024 10/04/2013 15:14

Claims (19)

• • • • • • • • • · · · · • ♦ V AT 69175 1. Cutting part (1 :) for drilling In a ceramic component, wherein the cutting part (1) is plate-shaped, in an insertion slot (21) of a shaft (20) can be inserted and at least one main cutting area (14) with a main cutting edge (2) and a tip (5) having a chisel edge (3), the cutting part (1) defining a longitudinal axis (L), a major axis (H) and a transverse axis (Q) perpendicular to each other and the geometric center of gravity of the main cutting area (14), wherein the transverse cutting edge (3) is formed by cutting two tip surfaces (6, 7) and the ends of the transverse cutting edge (3) are defined by two spotting surfaces (8, 9) which together with the tip surfaces (6, 7 ) each form a first tip main cutting edge (11) and a second tip main sewing head (13), the center point (5) of the transverse cutting edge (3) being spaced from the longitudinal axis (L) by an eccentricity measure (e) of at least 1% of the nominal diameter of the cutting edge on the other hand (1) is offset in the direction of the transverse axis (Q), so that the first tip main cutting edge (11) is shorter than the second tip main cutting edge (13). Second cutting part (1) according to claim 1, wherein one end of the transverse cutting edge (3) on the longitudinal axis (L). The cutting part (1) according to claim 1 or 2, wherein the degree of eccentricity (e) is greater than 1.5% of the nominal diameter of the cutting part (1). 4. cutting part (1) according to claim 1 or 2, wherein the Exzentrizitätsmaß (e) is greater than 2% of the nominal diameter of the cutting part (1). P.018 / 024 10/04/2013 15:14 15 / 25R887 2/4 AT 69175 5. cutting part (1) according to claim 1 or 2, wherein the Exzentrizitätsmaß (e) is greater than 3% of the nominal diameter of the Schneidcnteils (1). 6. cutting part (1) according to claim 1 or 2, wherein the Ex-centrizitätsmaß (e) is greater than 4% of the nominal diameter of the cutting part (1). 7. cutting part (1) according to claim 1 or 2, wherein the Ex-Zentri zLtätsmaß (e) is greater than 5% of the nominal diameter of the cutting part (1). 8. blade (1) according to one of claims 1 to 7, wherein the tip surfaces (6, 7) define a point angle (a) which is greater than 90 °. 9. Schneidenteii (1) according to claim 8, wherein the apex angle (ötj is 100 °. 10. cutting part (1) according to one of claims 1 to 8, wherein the Ausspitzungsflächen (8, 9) define a AusspitZungswinkel (ß), which is smaller than 90 °. 11. cutting part (1) according to claim 10, wherein the AusspitZungswinkel (ß) is 60 °. The cutting part (1) according to any one of claims 1 to 11, wherein an edge (16) defined by the cut of the longer, second pointed main cutting edge (13) forming the recess surface (8) with a side surface of the cutting part (1). with an axis containing the major axis (H) and the transverse axis (Q) defined an angle which is in the range of 5 ° to 25 °. P. 019/024 10704/2013 15:14 16/25 * 887 10.04.2013 Wed 15:07 TBK +49 89 54469290 ID: # 64173 Page 20 of 24 ·: · · · · · · · 3/4 AT 69175 13. cutting part (1) according to one of claims 1 to 12, wherein the main cutting area (14) has two cylinder cutting edges (4) at the tip (b) opposite end and two tapered blades (2) between the tip (5) and cylinder cutting edge (4) , wherein the cone cutting edges (2) and the cylinder cutting edges (4) are rectilinear. 14. A drill bit (100) having a shank (20) and a cutting part (1) according to one of claims 1 to 13, which is inserted into and connected to an insertion slot (21) at the front end of the shank (20). A drill (100) according to claim 14, wherein the diameter of a clamping portion of the shank (100) opposite the insertion slot (21) is greater than the nominal diameter of the cutting part (1). 16. A drill bit (100) according to claim 14 or 15, wherein an insertion slot (21) opposite clamping portion of the shaft (100) has one or more clamping surfaces. A method of manufacturing a cutting part (1) according to any one of claims 1 to 13, comprising the steps of: providing a green sheet defining a longitudinal axis (L), a major axis (H) and a transverse axis (Q) perpendicular to each other and passing through the geometrical center of gravity of the green slab, introducing two main cutting edges (2) on opposite sides of the raw slab in the direction of the main axis (H), the main cutting edges (2) approaching each other in the direction of the longitudinal axis, P. 020/024 10 / 04/2013 15:15 17/251887 TBK +49 89 54469290 10.04.2013 Wed 15:07 ID: # 64173 Page 21 of 24 TBK +49 89 54469290 10.04.2013 Wed 15:07 ID: # 64173 Page 21 of 24 • AT 69175 *** 4/4 * inserting two tip surfaces (6, 7), through the waste of which a transverse cutting edge (3 ), and introducing two Abußpitzungsflächen (8, 9) through the end of the Querschn 3) and together with the tip surfaces (6, 7) each form a first tip main cutting edge (11) and a second tip main cutting edge (13), wherein the two outer tapering surfaces (8, 9) are introduced such that the Center point (5) of the transverse cutting edge (3) is offset from the longitudinal axis (L) by an eccentricity meaure of at least 1% of the nominal diameter of the cutting part (1) in the direction of the transverse axis, such that the first peak main cutting edge (11) is shorter than the second Tip main cutting edge (13) is. 18. The method according to claim 17, wherein the introduction of the tip surfaces (6, 7) and the Ausspit-zungsflächen (8, 9) is effected by grinding with the end face of a cup wheel. 19. A method according to claim 17 or 18, wherein the green sheet has a curved main cutting edge, further comprising the step of grinding the curved main cutting edge into a straight-line cut-off 10/04/2013 15:15 18/251887 P.021 / 024