Four-edged drill

Abstract

The invention relates to a four-edged drill having two long main cutting edges, arranged in a point-symmetric manner with regard to the axis of rotation, which each extend from an outer circumferential cutting corner to a chisel edge in the middle of the drill tip, and two short main cutting edges, arranged in a point-symmetric manner with regard to the axis of rotation, which each extend from an outer circumferential cutting corner in the direction of the middle of the drill tip. According to the invention, each long main cutting edge has an outer partial cutting edge, extending from the cutting corner as far as a shoulder, and an inner partial cutting edge, extending from the shoulder as far as the chisel edge, said inner partial cutting edge having a greater cutting height (Δx) than the outer partial cutting edge and the short main cutting edges.

Claims

1. A four-edged drill, with two long main cutting edges arranged in a point symmetrical manner relative to an axis of rotation, which each extend from an outer circumferential cutting corner to a chisel edge in a middle of a drill tip, and two short main cutting edges arranged in a point symmetrical manner relative to the axis of rotation, which each extend from an outer circumferential cutting corner in the direction of the middle of the drill tip, each long main cutting edge having an outer partial cutting edge extending from the outer circumferential cutting corner up to a shoulder, and an inner partial cutting edge extending from the shoulder as far as the chisel edge, which have a greater cutting height than the outer partial cutting edge and the short main cutting edges.

2. The drill according to claim 1, wherein each outer partial cutting edge ends outside of a core of the drill.

3. The drill according to claim 1, wherein each short main cutting edge ends outside of a core of the drill.

4. The drill according to claim 1, wherein the short main cutting edges are longer than the outer partial cutting edges.

5. The drill according to claim 1, wherein a core diameter measures 0.4 to 0.6 times the nominal diameter of the drill.

6. The drill according to claim 1, wherein each inner partial cutting edge is corrected over its entire length by a point thinning section.

7. The drill according to claim 6, wherein each inner partial cutting edge runs at an obtuse angle to the outer partial cutting edge of the same main cutting edge.

8. The drill according to claim 1, wherein the chisel edge is point thinned.

9. The drill according to claim 1, wherein the outer partial cutting edges and the short main cutting edges have an identical rake angle.

10. The drill according to claim 1, wherein the outer partial cutting edges and the inner partial cutting edges have an identical rake angle.

11. The drill according to claim 1, wherein the outer partial cutting edges and the short main cutting edges have a defined cutting height difference.

12. The drill according to claim 11, wherein the short main cutting edges have a larger cutting height than the outer partial cutting edges.

13. The drill according to claim 1, wherein the short main cutting edges, the inner partial cutting edges and the outer partial cutting edges each run along a straight line.

14. The drill according to claim 1, wherein the main cutting edges each lie in front of a diametral plane of the drill as viewed in a rotational or cutting direction.

15. The drill according to claim 1, wherein the rake angle of the main cutting edges is greater than or equal to 0°.

16. The drill according to claim 1, wherein the shoulder is axially and/or radially relief ground.

17. The drill according to claim 1, wherein the drill comprises chip grooves that run along a straight line.

18. The drill according to claim 1, wherein the drill comprises an interior cooling lubricant supply system with outlet openings that lie in an area of free surfaces of the main cutting edges.

19. The drill according to claim 1, wherein four main cutting edges are ground into a cutting head attached to a shank.

20. The drill according to claim 1, wherein the four-edged drill is a deep hole drill.

21. The drill according to claim 1, wherein a core diameter measures about 0.5 times the nominal diameter of the drill.

22. The drill according to claim 1, wherein the drill comprises an interior cooling lubricant supply system with outlet openings that lie in an area of secondary free surfaces of the main cutting edges.

Description

(1) A drill according to the invention will be described in more detail below based on an exemplary embodiment shown in the drawings. Shown on:

(2) FIG. 1 is a front view of a drill tip of a four-cutting edged deep-hole drill;

(3) FIGS. 2 to 4 are side views of the drill tip from FIG. 1;

(4) FIGS. 5 and 6 are perspective side views of the drill tip from FIG. 1;

(5) FIG. 7 is a front view of the drill tip rotated by 90° relative to the front view from FIG. 1;

(6) FIGS. 8 and 9 are side views of the drill tip from FIG. 7;

(7) FIG. 10 is a perspective side view of the drill tip from FIG. 7;

(8) FIG. 11 is a side view of a blank of the four-edged deep-hole drill according to the invention;

(9) FIGS. 12 to 15 is a respective side view and top view of a shank, a retaining ring and a clamping sleeve of the four-edged drill; and

(10) FIG. 16 is a side view and a top view of a cutting head blank of the four-edged drill.

(11) In the exemplary embodiment shown on the figures, the drill is designed as a four-edged deep-hole drill 10.

(12) FIG. 11 shows a side view of a blank of the deep-hole drill 10, which consists of a shank 13, the cutting head 12 soldered to the shank 10, a clamping sleeve 14 positively joined to the shank 13, and a retaining ring 15 that fixes the shank 13 to the clamping sleeve 14 via jacketing and soldering. The shank 11, clamping sleeve 14 and retaining ring 15 are shown in more detail on FIGS. 12 to 15. A blank of the cutting head is shown in more detail on FIG. 16. As shown on FIGS. 11, 12 and 16, the shank 11 and cutting head 12 are each designed with straight grooves.

(13) In order to connect the cutting head 12 with the shank 13, the end of the shank 13 on the cutting head side has a V-shaped notch 16 referred to as a soldering prism, into which a chisel tip 17 formed on the shank-side end of the cutting head 12 is positively accommodated and materially connected with the shank 13 through soldering.

(14) As shown by the top views on FIGS. 12 and 13, the shank has four webs 22 to 18 arranged at an angular distance of 90°, between which is formed a respective chip groove 19 running along a straight line parallel to the axis of rotation 1.

(15) Corresponding to the number of chip grooves 19, the clamping sleeve 14 shown on FIG. 15 has four axial, roughly quadrantal segment-shaped projections 21, which are each positively inserted into one of the chip grooves 19 so as to connect the shank 13 with the clamping sleeve 14. Reference number 14a denotes a clamping surface over which the clamping sleeve 14 can be non-rotatably clamped in a chuck (not shown).

(16) The retaining ring 15 shown on FIG. 14 rests on the interface created in this way between the clamping sleeve 14 and shank 13. In order to fix the shank 13 on the clamping sleeve 14, the retaining ring 15 is soldered with the shank 13 and clamping sleeve 14.

(17) The cutting head 12 is fashioned out of the cutting head blank 24 shown on FIG. 16. The V-shaped dashed line marks the chisel tip 17 of the cutting head 12 to be attached to the V-shaped notch of the shank 16. Analogously to the shank 13, the cutting head 12 has four webs 22 arranged at an angular distance of 90°, between which is formed a respective essentially V-shaped chip groove 23 running along a straight line parallel to the axis of rotation 1 (see top view on FIG. 16).

(18) In the state attached to the shank 13 (see FIG. 11), the chip grooves 19 of the shank axially adjoin the chip grooves 23 of the cutting head 12. As evident from FIG. 11, the cutting head 12 has a somewhat larger diameter than the shank 13.

(19) Shown by dashed lines on FIGS. 12 and 16 is an interior cooling lubricant supply system comprised of a central main channel 25 that extends through the clamping sleeve 14 and shank 13 as far as the cutting head 12, and, corresponding to the number of webs 22 or chip grooves 23, four branch channels 26, which branch away from the main channel 25 immediately after the joint between the shank 13 and cutting head 12, and outlet openings 27, which lie in the area of the subsequently described free surfaces of the four main cutting edges of the cutting head 12. The main channel 25 and branch channels 26 each run along a straight line (holes).

(20) FIGS. 1 to 10 show how the drill tip 11 of the four-edged cutting head 12 is ground, which in the state shown on FIG. 11 is done on the end faces of the cutting head 12. FIGS. 1 to 10 thus present grinding instructions for grinding the drill tip 11 of the cutting head 12.

(21) As shown on FIG. 1, four main cutting edges 33 (a main cutting edge 33 per web 22) are formed on the drill tip 11. In the exemplary embodiment shown, the four main cutting edges 33 comprise two longer or (in the following:) long main cutting edges 33 arranged in a point symmetrical manner relative to the axis of rotation 1, which each extend from an outer circumferential cutting corner 31c as far as a chisel edge 34 (see FIG. 7) in the middle of the drill tip 11, and two shorter or (in the following:) short main cutting edges 30 arranged in a point symmetrical manner relative to the axis of rotation, which each extend from an outer circumferential cutting corner 30c in the direction of, but not as far as, the middle of the drill tip 11. According to the invention, each long main cutting edge 33 has an outer partial cutting edge 31 extending from the cutting corner 31c as far as a step or (in the following:) a shoulder 31d (see FIG. 2) and an inner partial cutting edge 32 extending from the shoulder 31d as far as the chisel edge 34.

(22) As viewed in the axial or feed direction of the deep-hole drill 10, the inner partial cutting edges 32 have a greater cutting height than the outer partial cutting edges 31 and the two short main cutting edges 30. The higher inner partial cutting edges 32 can thus also be referred to as pre- and solid drilling edges, which allow the deep-hole drill to cut into solid materials, while the outer partial cutting edges 31 and the short main cutting edges 30 can also be referred to as reaming cutting edges, which are used to bore out the hole generated by the inner partial cutting edges 32 to the nominal diameter of the deep-hole drill.

(23) The higher inner partial cutting edges 32 lie in the area of the drill core 35 of the deep-hole drill 10, while the outer partial cutting edges 31 and the two short main cutting edges 30 lie outside of the core 35. The outer partial cutting edges 31 and the short main cutting edges 30 thus end radially outside of the core 35 or—viewed from the outside in—in front of the core 35. In the exemplary embodiment shown, the diameter of the core 35 measures about 0.4 to 0.6 times, in particular about 0.5 times, the nominal diameter of the deep-hole drill.

(24) The cutting height difference Δx between the inner partial cutting edges 32 and the outer partial cutting edges 31 achieved by the shoulder 31d lies within a range of 0.02 to 0.1 times, in particular of 0.04 to 0.8 times, the nominal diameter of the deep-hole drill 10. As evident from FIG. 2, the shoulder 31d is axially relief ground. For example, the angle indicated with ∈ measures 90°.

(25) A secondary cutting edge that runs along a straight line and is not described here in any greater detail adjoins each of the cutting corners 31c, 30c in the usual manner.

(26) As shown on FIGS. 1 to 10, the outer partial cutting edges 31, the inner partial cutting edges 32 and the short main cutting edges 30 are each straight in design.

(27) In addition, the two outer partial cutting edges 31, the inner partial cutting edges 32 and the short cutting edges 30 are arranged at the same point angles. In the exemplary embodiment, the point angles of the outer partial cutting edges 31, inner partial cutting edges 32 and short main cutting edges 30 indicated with δ.sub.31, δ.sub.32, δ.sub.30 on FIG. 2 and FIG. 8 lie within a range of 140° to 150°, in particular at 145°.

(28) In addition, the two inner partial cutting edges 32 are arranged at the same cutting height. In addition, the outer partial cutting edges 31 are arranged at the same cutting height, and the short main cutting edges 30 are arranged at the same cutting height. In the exemplary embodiment shown, however, the short main cutting edges 30 have a defined cutting height difference relative to the outer partial cutting edges 31, which can lie within a range of 0.01 to 0.03 mm, in particular at 0.02 mm.

(29) In addition, the inner partial cutting edges 32, the outer partial cutting edges 31 and the short main cutting edges 30 lie in front of a diametral plane of the deep-hole drill 10 viewed in the cutting direction, i.e., they cut “before the middle”.

(30) The rake angle not indicated on the figures for all main cutting edges, i.e., the inner partial cutting edges 32, the outer partial cutting edges 31 and the short main cutting edges 30, is equal to or greater than 0° in the exemplary embodiment shown.

(31) On FIG. 7, reference numbers 31a, 32a and 30a indicate primary free surfaces, and reference numbers 31b, 32b and 30b indicate secondary free surfaces relative to the outer partial cutting edges 32, the inner cutting edges 32 or the short main cutting edges 30.

(32) As further shown on FIG. 7, the outlet openings 27 of the four branch channels 26 of the aforementioned interior cooling lubricant supply system each lie in the area of the free surfaces, in particular in the area of the secondary free surfaces, of an allocated main cutting edge.

(33) Visible on FIGS. 1 to 10 are grinded point thinning sections 40, 41, 42, which result in a shortening of the chisel edge 34 (see FIG. 7), and a correction of the inner partial cutting edges 32 or of the core area lying in front of a short main cutting edge 30 in the sectional or rotational direction. Visible on FIG. 1 or 7 are the point thinning sections grinded into the drill tip 11. The point thinning section 41 corrects the inner partial cutting edge 32, so that the inner partial cutting edge 32 in the exemplary embodiment shown runs at an angle to the outer partial cutting edge 32 of the same main cutting edge. The point thinning section 32 causes the core region lying in front of a short main cutting edge 30 in the rotational or sectional direction to be grinded in.

(34) The point thinning sections are grinded in using grinding wheels (not shown). The cross sectional contour of each point thinning section is thus determined by the shape of the respectively used grinding wheel. FIGS. 6, 9 and 10 describe the grinded in portions, wherein FIGS. 5, 6 and 10 show the deep-hole drill 10 in a position and alignment in which the grinded in portions extend in a direction perpendicular to the leaf level, while FIGS. 3, 4 and 9 show the angle of inclination α.sub.40, α.sub.41, α.sub.42 of the grinded in portions relative to a plane perpendicular to the rotational axis 11 of the deep-hole drill 10.

(35) In particular, FIGS. 3 and 5 show a grinded in portion for generating the point thinning section 40 that shortens the chisel edge 34, FIGS. 4 and 6 show a grinded in portion for generating the point thinning section 41 that corrects the inner partial cutting edge 31, and FIGS. 9 and 10 show a grinded in portion for generating the point thinning section 42. The transverse contours of the grinded in portions or point thinning sections 40, 41, 42, and thus the shapes of the respectively used grinding wheels, are discernible on FIG. 5, 6 or 10.

(36) As shown on FIGS. 5, 6 and 10, the point thinning sections 40, 41 or 42, which each empty into an allocated chip groove 23 of the deep-hole drill 10, have a roughly V-shaped cross section with a rounded base, the opening angle of which measures β.sub.40 or β.sub.41 (see FIGS. 5, 6), or a cross section in the form of a flat trough (see FIG. 10). In the exemplary embodiment shown, the opening angle β.sub.40 or β.sub.41 lies within a range of 75° to 85°, e.g., at 80°.

(37) In the exemplary embodiment shown, the aforementioned angles of inclination α.sub.40, α.sub.41, α.sub.42 relative to a plane perpendicular to the axis of rotation 11 of the deep-hole drill 10 lie between 30° and 50°, wherein the angle of inclination α.sub.40 can measure 35°, the angle of inclination α.sub.41 can measure 40°, and the angle of inclination α.sub.42 can measure 48°, for example.

(38) Of course, a drill according to the invention can be modified from the exemplary embodiment described above. For example, the point thinning section described based on FIGS. 1 to 10 can basically be used for drills of any length. Therefore, a drill according to the invention is not necessarily limited to a deep-hole drill.

(39) Contrary to the exemplary embodiment described, a drill according to the invention, for example a deep-hole drill, can further be made out of a single piece, i.e., have a monolithic design.

(40) In addition, a drill according to the invention, for example a deep-hole drill, can be spirally grooved.

(41) Contrary to the described exemplary embodiment, the webs 22 (i.e., the chip grooves 23 or the main cutting edges 30, 33) can be arranged at angular distances different from 90°. Diametrically opposing main cutting edges 33 or 30 can here be arranged in a point symmetrical manner.

(42) In the simplest case, a straight-grooved, four-edged drill, in particular a deep-hole drill, constitutes a separate subject matter independent of the feature combination indicated in claim 1, for which protection can still be claimed at a later time, either in the present application, a subsequent application, by way of a partial application or a split-off utility model.

(43) An independent main claim can thus be directed at a straight-grooved drill, in particular a deep-hole drill, with a drill tip having four main cutting edges. As opposed to the drill from U.S. Pat. No. 5,173,014 discussed at the outset, this type of a drill, in particular a deep-hole drill, can be manufactured more easily and cost-effectively. This main claim can be followed by dependent claims, which relate to additional configuration features of the four-edged drill that arise from the claims, specification and/or drawings of the present application.

(44) For example, the subject matter of a dependent claim can involve the four main cutting edges of the drill being comprised of two long main cutting edges arranged in a point symmetrical manner relative to the axis of rotation, which each extend from an outer circumferential cutting corner as far as a chisel edge in the middle of the drill tip, and two short main cutting edges arranged in a point symmetrical manner relative to the axis of rotation, which each extend from an outer circumferential cutting corner in the direction of the middle of the drill tip.

(45) The subject matter of another dependent claim can be that the four main cutting edges of the drill define a tip downwardly offset in the axial direction in the core. For example, the tip can be achieved by having each long main cutting edge have an outer partial cutting edge extending from the cutting corner as far as a shoulder and an inner partial cutting edge extending from the shoulder as far as the chisel edge, which has a larger cutting height than the outer partial cutting edge and the short main cutting edges.

(46) The subject matter of another dependent claim can be that a respective outlet opening for cooling lubricant be allocated to the four main cutting edges, which lies in back of a respective main cutting edge in the area of the free surface in the rotational or cutting direction.