FLAT DRILL

Abstract

A flat drill (1) with a shank (6) and a cutting part (8) with front-side main cutting edges (16), which each extend in a plane transversely to the drill axis (3) from a cutting edge corner (22) into the drill center. The flat drill (1) has exactly three main cutting edges (16), which converge at the drill axis (3).

Claims

1. A flat drill with a shank and a cutting part with front-side main cutting edges, which each extend in a plane transversely to the drill axis from a cutting edge corner into a drill center, characterized by three main cutting edges, which converge at the drill axis.

2. The flat drill according to claim 1, viewed in the direction of rotation of the drill, the main cutting edges in each case lie at least partly in front of a plane containing the drill axis and the respective cutting edge corner and the course of the main cutting edges is in each case corrected by means of a point thinning in the region of a drill core.

3. The flat drill according to claim 2, wherein the main cutting edges in each case run in a crescent-shaped manner from the point thinnings in the direction of the cutting edge corners.

4. The flat drill according to claim 2, characterized by chip surfaces, which adjoin the main cutting edges and which each have a positive axial chip angle in the region from the point thinning all the way to the cutting edge corners.

5. The flat drill according to claim 2, wherein the chip surfaces, which adjoin the main cutting edges, each have an axial chip angle of 0 in the region of the point thinnings.

6. The flat drill according to claim 1, characterized by free surfaces, which adjoin the main cutting edges and which are in each case formed of a first free surface adjoining the main cutting edge and a second free surface adjoining the first free surface with a larger clearance angle than the first free surface.

7. The flat drill according to claim 6, characterized by cooling lubricant channel exit openings lying in the free surfaces.

8. The flat drill according to claim 1, characterized by helically running chip flutes.

Description

[0029] Further details, features and advantages follow from the following description of an embodiment on the basis of the drawings, in which:

[0030] FIG. 1 shows a flat drill according to an embodiment in a side view;

[0031] FIG. 2 shows a front view of the flat drill from FIG. 1;

[0032] FIG. 3 shows a detailed view of the flat drill from FIG. 2;

[0033] FIG. 4 shows a side view of a cutting part of the flat drill from FIG. 1; and

[0034] FIG. 5 shows a perspective view of the flat drill from FIG. 1.

EMBODIMENT

[0035] A right-handed flat drill with three cutting edges of one embodiment, which has a tool shank 6 extending along a drill axis 3 for clamping into a tool chuck as well as a cutting part 8, is identified with reference numeral 1 in FIGS. 1 to 5. The cutting part 8 has three chip flutes 10 running at a positive angle of twist and three webs 14 running parallel to the chip flutes 10 from a drill front in the direction of the tool shank 6. Each web 14 forms a cutting wedge on its front frontal end, which is illustrated on the left in FIG. 1. The cutting wedge has a main cutting edge 16, the course of which is corrected by means of a point thinning 20 in the region of the drill center or of the drill core, respectively. The flat drill 1 of the embodiment thus has exactly three main cutting edges 16, which converge at the drill axis 3, as is shown in FIG. 3.

[0036] As can furthermore be seen from FIGS. 2 and 3, each main cutting edge 16 has a first main cutting edge section 16a, which, starting at the drill axis 3, at which the main cutting edges 16 converge in one point, all the way to the beginning of the point thinning 20, a second main cutting edge section 16b, which is angled to the first main cutting edge section 16a, in the region of the point thinning 20, as well as a third main cutting edge section 16c, which runs in a crescent-shaped manner from the point thinning 20 all the way to a cutting edge corner 22 (not shown completely in FIG. 3).

[0037] At the cutting edge corner 22, the main cutting edge 16 or the third main cutting edge section 16c, respectively, merges into a secondary cutting edge 24, which is provided for the bore finishing and which is adjoined by a guide bevel 28 in the circumferential direction of the flat drill 1.

[0038] The front-side main cutting edges 16 of the flat drill 11, which each have the first main cutting edge section 16a, the second main cutting edge section 16b and the third main cutting edge section 16c, extend in a plane, which is perpendicular to the drill axis 3 or which lies transversely to the drill axis 3, respectively. As shown in particular in FIG. 4, a tip angle of the flat drill 1 is exactly 180. It can furthermore be seen from FIG. 2 that the main cutting edges 16, viewed in the direction of rotation 5 of the drill, in each case lie in front of a plane (not shown) (in front of center) containing the drill axis 3 and the respective cutting edge corner 22 in the main cutting edge section 16b designed by the point thinning 20, and lie partly behind the plane (not shown) (behind center) containing the drill axis 3 and the respective cutting edge corner 22 in the radially outer main cutting edge section 16c due to the crescent-shaped course.

[0039] Viewed against the direction of rotation of the flat drill 1, each main cutting edge 16 is adjoined by a first free surface 28, which has a first clearance angle. Against the direction of rotation of the flat drill 1, a second free surface 30 adjoins the first free surface 28, the second clearance angle of which is larger than the first clearance angle of the first free surface 28. As shown in FIGS. 2 and 5, a cooling lubricant channel exit opening 32 for the exit of cooling lubricant for cooling and lubricating the main cutting edges 16 during the drilling process in each case leads into the second free surfaces 30. In the shown embodiment, the first and second free surfaces 28 and 30 are in each case surfaces, which are partly ground in a planar manner.

[0040] Viewed in the direction of rotation of the flat drill 1, each main cutting edge 16 is adjoined by a chip surface, which has a positive axial chip angle in the region from the point thinning 20 all the way to the cutting edge corner 22, i.e., in the region of the third main cutting edge section 16c, which runs in a crescent-shaped manner, and an axial chip angle of 0 in the region of the point thinning 20, i.e. in the region of the second main cutting edge section 16b.

[0041] By providing exactly three main cutting edges 16, the stress is distributed to the three main cutting edges 16 in the case of the flat drill 1 of the embodiment. Compared to a conventional flat drill with only two main cutting edges, the stress for each main cutting edge 16 reduces from 50% to 33.33% in the drilling process and thus decreases by 33.33% for each main cutting edge. The durability of the flat drill 1 and thus its service life increases due to the lower stress. The flat drill 1 can furthermore be centered better during the drilling process by means of the additional third main cutting edge 16, which leads to more precise bores. Lastly, the third main cutting edge 16 provides for faster drilling speeds and for a more efficient chip removal because the additional main cutting edge 16 can break chips and can remove the chip material more quickly, whereby the risk of blockages and an overheating of the flat drill 1 is reduced.

LIST OF REFERENCE NUMERALS

[0042] tip angle [0043] 1 flat drill [0044] 3 drill axis [0045] 5 direction of rotation of the drill [0046] 6 tool shank [0047] 8 cutting part [0048] 10 chip flute [0049] 14 web [0050] 16 main cutting edge [0051] 16a first main cutting edge section [0052] 16b second main cutting edge section [0053] 16c third main cutting edge section [0054] 20 point thinning [0055] 22 cutting edge corner [0056] 24 secondary cutting edge [0057] 26 guide bevel [0058] 28 first free surface [0059] 30 second free surface [0060] 32 cooling lubricant channel exit opening