Drill head

Abstract

The drill head (2) extends along a rotational axis (24) in the axial direction (22) and has a central area (6) on the front with first main cutting edges (26), an intermediate area (8) connecting thereto, and an outer area (10) in turn connecting thereto with second main cutting edges (30). The intermediate area (8) in this case expands in the axial direction (22) toward the outer area (10) and in particular forms an expanding conical shell. A centering effect is hereby achieved via the intermediate area (8).

Claims

1. A drill head extending along a rotational axis in an axial direction and comprising: a central area on a front portion of the drill head, with first main cutting edges which extend up to a first radius; an outer area, offset rearwardly in the axial direction relative to the central area, with second main cutting edges extending up to a second outer radius; and an intermediate area extending in the axial direction, which terminates at the central area and connects the central area with the outer area, the intermediate area having intermediate cutting edges formed thereon, the intermediate cutting edges connecting the first main cutting edges with the second main cutting edges, wherein the intermediate area extends in the axial direction up to the outer area at an inclination angle, the inclination angle being in a range between 3° and 15° in relation to the rotational axis wherein the second main cutting edges are oriented with respect to one another at the same point angle as the first main cutting edges.

2. The drill head according to claim 1, wherein the intermediate area expands conically.

3. The drill head according to claim 1, wherein the first radius of the central area is in a range between 0.25 to 0.8 times that of the outer radius.

4. The drill head according to claim 1, wherein the intermediate area extends in the axial direction over an axial length in a range of from 0.1 mm to 5 mm.

5. The drill head according to claim 1, wherein the first main cutting edges of the central area are oriented at a point angle with respect to one another, which is in a range of from 90° to 180°.

6. The drill head according to claim 5, wherein the point angle is about 140°.

7. The drill head according to claim 1, wherein a chip flute is placed in the central area.

8. A drill head extending along a rotational axis in an axial direction and comprising: a central area on a front portion of the drill head, with first main cutting edges which extend up to a first radius, the first main cutting edges being oriented at a first point angle with respect to one another in a range of from 90° to 180°; an outer area, offset rearwardly in the axial direction relative to the central area, with second main cutting edges extending up to a second outer radius, the second main cutting edges being oriented at a second point angle with respect to one another, the second point angle being equal to the first point angle; and an intermediate area extending in the axial direction, which terminates at the central area and connects the central area with the outer area, wherein the intermediate area extends in the axial direction up to the outer area at an inclination angle, wherein the inclination angle is in the range between 3° and 15° in relation to the rotational axis; and wherein the intermediate area has intermediate cutting edges formed thereon, the intermediate cutting edges connecting the first main cutting edges with the second main cutting edges.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a drill head in a side view, which is designed as a replaceable drill head for a modular drilling tool.

(2) FIG. 2 illustrates a drill head comparable to that in FIG. 1, with a view of its drill face.

(3) FIG. 3 illustrates an enlarged, diagrammed representation of the area indicated with a circle in FIG. 1.

DETAILED DESCRIPTION

(4) FIGS. 1 and 2 show a drill head 2 which, in some embodiments, is formed as a replaceable drill head for insertion into a carrier (which is not shown in more detail here) of a modular drilling tool.

(5) The drill head has a drill face 4 as the front face. This drill face 4 is wholly formed by three sub-areas, namely a central area 6 on the front, an intermediate area 8, and an outer area 10. A total of two chip flutes 12 are introduced into the drill head, which chip flutes 12 extend in the shape of a helix in the exemplary embodiment. These are typically continued in a shaft area of the carrier.

(6) The drill head 2 has a coupling pin 14 on its side opposite the drill face 4, with a connecting lead-in pin 16. A detachable connection with the carrier is formed via the coupling pin 14. A respective secondary cutting edge 18, at which a support or guide chamfer 20 connects to a drill back of the drill head 2 in the circumferential direction, runs along the chip flute 12.

(7) The entire drill head 2 extends in an axial direction 22 along a rotational axis 24 around which it rotates during operation. The rotational axis 24 defines a center axis.

(8) The central area 6 on the front has two first main cutting edges 26 which, starting from a center, extend in approximately a radial direction outward up to a first radius r.sub.1. Intermediate cutting edges 28 of the intermediate area 8 adjoin these first main cutting edges 26. Second main cutting edges 30 of the outer area 10, which extend up to a nominal radius r.sub.2 of the drill head 2, then in turn adjoin these first main cutting edges. Thus, the radius of the drill hole created is defined via the nominal radius r.sub.2. In the exemplary embodiment, the drill head 2 is formed rotationally symmetrically around the rotational axis 24 with respect to a 180° rotation.

(9) As can particularly be seen from the enlarged, diagrammed representation in FIG. 3, the intermediate area 8 is formed overall as a conically expanding intermediate area 8 in the axial direction 22, thus in the direction from the drill face 4 to a rearward area. Thus, the intermediate area 8 is formed wholly as an expanding conical shell. The intermediate area 8 in this case is oriented at an inclination angle α with respect to the axial direction 22. The inclination angle α is preferably in a range of between 3° and 15°, and approximately 11° in the exemplary embodiment.

(10) At the same time, both the first main cutting edges 26 and the second main cutting edges 30 are oriented at a point angle β with respect to one another, which is preferably in a range of between 120° and 150° and is approximately 140° in the exemplary embodiment. Alternatively, the two point angles β are formed differently. In this case, the point angle β of the first main cutting edges 26 is greater than or less than the point angle β of the second main cutting edges 30.

(11) The first radius r.sub.1 is preferably in a range of between 0.25 to 0.8 times that of the nominal radius r.sub.2. Preferably, it tends to be in the lower range, i.e. in a range of between 0.25 and 0.4 times that of the nominal radius, for example. In the exemplary embodiment, it is about one-third that of the nominal radius r.sub.2.

(12) The intermediate area 8 further extends over an axial length L which as a whole is of comparatively short dimension, at least as compared to the conventional designs of step drills. It is preferably in a range between 0.1 mm and 2 mm. Depending on the material to be machined, the axial length L may also be more than this, for example up to a maximum of 5 mm.

(13) The embodiment of the drill face 4 described here, with the intermediate area 8 expanding at an inclination angle α, may in principle be formed with different face geometries for drills that are known per se. Thus, FIG. 2 shows as an example a grinding face as a type of conical shell cut, in which a respective effective main cutting edge respectively connects to an approximately conical flank 32. In addition, a point thinning 34 is introduced into this flank in a known manner to taper a core area of the drill. An effective main cutting edge here is understood to be in particular the uninterrupted, continuous cutting edge which is formed by the three sub-areas: first main cutting edge 26; intermediate cutting edge 28; and second main cutting edge 30.

(14) Furthermore, it is to be learned from FIG. 2 that—given the grinding face of the drill face 4 selected here—the two first main cutting edges 26 are connected to one another via a crosscut, which means that an approximately S-shaped cutting edge is formed.

(15) In addition to the grinding face of the drill face 4 shown here, what are known as four-surface grinding faces etc. that are known per se are also used for the drill face 4.

(16) Due to its conical design, the intermediate area 8 forms a centering area and has a centering effect during the drilling process. Due to its inclination, it engages with the work piece to be machined. As a result of the intermediate cutting edges 28, there is machining of the work piece in the intermediate area 8. This causes material removal forces to occur which have a radial component in the direction of the rotational axis 24. Due to the rotationally symmetrical design, these material removal forces that occur have an effective centering effect, and the entire drill head 2—and thus the drill—is effectively centered.