Metal drill bit and method using the same

Abstract

The present invention relates to a drill 10 for drilling a blind hole having a blind hole diameter and a blind hole depth, which is guided by hand to a workpiece made of metal, and includes a shaft 20 defining a drilling direction 30 and having a rotation axis oriented in the drilling direction. The shaft has a cutting edge 50 at its end facing the drilling direction and an abutting shoulder 55 at a certain distance from the cutting edge, which is measured in the direction opposite to the drilling direction and defines the blind hole depth. The cutting edge defines the blind hole diameter by rotation about the rotation axis. The shaft has an envelope circle diameter that varies along the rotation axis and is larger than the blind hole diameter at the abutting shoulder. The shaft has a first shaft portion 40 adjacent to the abutting shoulder in the direction opposite to the drilling direction. The first shaft portion extends up to the abutting shoulder, and its envelope circle diameter increases starting from the abutting shoulder in the direction opposite to the drilling direction.

Description

Technical Field

[0001] The present invention relates to a drill bit for drilling a blind hole with a manual guide into a metal workpiece.

Background Art

[0002] There are known drill bits having a shank with a cutting edge and a stop shoulder that define a drilling direction, the distance between the cutting edge and the stop shoulder defining the blind hole depth. The stop shoulder usually has an edge and creates a hole with a sharp boundary in the cover layer of the workpiece in question. A sealing ring that later covers the hole can be damaged by its edge.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to provide a drill bit that reduces the risk of damage to the sealing element.

Means for Solving the Problems

[0004] This object is achieved by a drill bit for hand-guiding a metal workpiece and drilling a blind hole having a blind hole diameter and a blind hole depth, the drill bit including a shank defining a drilling direction and having a rotational axis oriented in the drilling direction, the shank having a cutting edge at its end facing the drilling direction, and having a stop shoulder at a certain distance from the cutting edge defining the blind hole depth and measured opposite to the drilling direction, the cutting edge defining the blind hole diameter by rotation about the rotational axis, the shank having an envelope circle diameter that varies along the rotational axis and is larger than the blind hole diameter at the stop shoulder, the shank having a first shank section adjacent to and reaching up to the stop shoulder opposite to the drilling direction, the envelope circle diameter starting from the stop shoulder and preferably increasing continuously opposite to the drilling direction. The shank preferably has two or more cutting edges at its end facing the drilling direction, which together define the blind hole diameter by rotation about the rotational axis, and particularly preferably are arranged symmetrically about the rotational axis.

[0005] The envelope circle diameter in the present invention is the diameter of the smallest possible circle that still completely envelopes the shank and has the center of the circle on the rotational axis. In other words, for any point along the rotational axis, the area of the envelope circle is the area covered by the shank when rotated about the rotational axis. In the case of a circular circumference line, the envelope circle diameter is equal to the diameter of the circumference line, i.e., the shank diameter. Deviation inside the circumference line from the circular shape does not affect the envelope circle diameter, while deviation outside increases the envelope circle diameter.

[0006] In a preferred embodiment, the shank has a centering point at its end facing the drilling direction through which the rotational axis extends.

[0007] In a preferred embodiment, the stop shoulder has a stop surface oriented perpendicular to the rotational axis and the point in the drilling direction.

[0008] In a preferred embodiment, the shank has a fixing section at its end facing away from the drilling direction for temporary fixation to the hand-held drilling machine. The fixing section is particularly preferably configured as an insertion end.

[0009] In a preferred embodiment, the first section has a conical shape. The opening angle of the conical shape is preferably at least 60°, particularly preferably at least 90° or at least 120°.

[0010] In a preferred embodiment, the first section extends along the axis of rotation over at least 0.5 mm, preferably at least 1.0 mm, particularly preferably at least 1.5 mm or at least 2.0 mm.

[0011] This object is also achieved by a method of attaching a fastening element to a workpiece, wherein the workpiece having a cover layer and the drill bit are provided as described above, the blind hole is drilled into the workpiece through the cover layer by the drill bit, the first shank section of the drill bit creates a hole in the cover layer that increases in size in the direction opposite to the drilling direction, and further, a fastening element having a sealing element is provided and pushed into the blind hole, and the sealing element is pressed against the hole in the cover layer. The fastening element is preferably screwed into the blind hole.

[0012] Hereinafter, the present invention will be described in more detail with reference to the drawings.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Figure 1 shows a side view of a drill bit 10 suitable for drilling a counterbore into a metal workpiece (not shown) to stop at a hand guide. The drill bit 10 includes a shank 20 that defines a drilling direction 30 and has a rotational axis directed in the drilling direction 30. The shank 20 has a cutting edge 50 and a further cutting edge (not shown) at its end facing the drilling direction 30, which are arranged symmetrically on opposite sides of each other and with respect to the rotational axis, and together define the counterbore diameter of the counterbore drilled by rotation about the rotational axis. Further, the shank 20 has a stop shoulder 55 with a stop surface 60 that is directed perpendicular to the rotational axis and faces the drilling direction 30. During the drilling of the counterbore, the stop shoulder 55 abuts against the surface of the workpiece, so that the distance between the stop surface 60 and the cutting edge 50, measured opposite to the drilling direction 30, defines the counterbore depth of the drilled counterbore. The shank 20 has an insertion end (not shown) for temporarily fixing it to a hand-held drilling machine at its end facing opposite to the drilling direction 30.

[0015] The shank 20 has an envelope circle diameter that varies along the rotational axis. At the stop shoulder 55, the envelope circle diameter is larger than the counterbore diameter. Further, the shank 20 has a centering point 70 at its end facing the drilling direction 30, through which the rotational axis extends. The entire shank 20 including the cutting edge 50 and the centering point 70 is integrally formed, so that the stop shoulder 55 and the cutting edge 50 are made of the same material, preferably metal or alloy, particularly preferably steel.

[0016] For the removal of metal chips generated during the drilling by the cutting edge 50 and the further cutting edge, the shank 20 has two helical grooves 90 that extend through the stop shoulder 55 and are bounded by the cutting edge 50 and the further cutting edge.

[0017] The shank 20 has a first shank section 40 that is adjacent to the stop shoulder 55 opposite to the drilling direction 30 and reaches up to the stop shoulder 55. In the first shank section 40, the envelope circle diameter starts from the stop shoulder 55 and continuously increases in the direction opposite to the drilling direction 30. The first shank section has a conical shape with an opening angle of 140° and extends along the rotation axis over 2.5 mm.

[0018] Figure 2 shows a workpiece 100 having a cover layer 110. The workpiece has a blind hole 120, which is generated, for example, by the drill bit 10 of FIG. 1. The first shank section of the drill bit generates a hole 130 in the cover layer, and the size of the hole 130 increases in the direction opposite to the drilling direction.

[0019] Figure 3 shows a drilling machine 150 having a bit holder 160 and a fastening element 170. The fastening element 170 has a sealing element 180 configured as a sealing ring and is pushed into, for example, the blind hole 120 of FIG. 2.

[0020] Figure 4 shows the workpiece 100 having the cover layer 110 after the fastening element with only the sealing element 190 is pushed into the blind hole 120. The sealing element 190 is pressed against the hole 130 in the cover layer, and the size of the hole 130 increases in the direction opposite to the drilling direction. Due to the conical shape of the hole 130, the sealing element 190 is protected from excessive loads.

[0021] The present invention has been described using the example of a metal drill bit. However, the drill bit according to the present invention is also suitable for other purposes.

Claims

1. A drill bit for drilling a blind hole having a blind hole diameter and a blind hole depth, guided to a metal workpiece, comprising a shank defining a drilling direction and having a rotational axis directed in said drilling direction, said shank having a cutting edge at its end facing in said drilling direction, and having a stop shoulder at a certain distance from said cutting edge, defining said blind hole depth and measured opposite to said drilling direction, said cutting edge defining said blind hole diameter by rotation about said rotational axis, said shank varying along said rotational axis and having an envelope circle diameter larger than said blind hole diameter at said stop shoulder, said shank having a first shank section adjacent to said stop shoulder in a direction opposite to said drilling direction and reaching up to said stop shoulder, in which first shank section said envelope circle diameter increases starting from said stop shoulder in a direction opposite to said drilling direction.

2. The drill bit according to claim 1, wherein said envelope circle diameter of said first shank section increases continuously in a direction opposite to said drilling direction.

3. The drill bit according to claim 1 or 2, wherein said first section has a conical shape.

4. The drill bit according to claim 3, wherein said opening angle of said conical shape is at least 60°, in particular at least 90°, in particular at least 120°.

5. The drill bit according to any one of claims 1 to 4, wherein said first section extends along said rotational axis over at least 0.5 mm, in particular at least 1.0 mm, in particular at least 1.5 mm, in particular at least 2.0 mm.

6. The drill bit according to any one of claims 1 to 5, wherein said shank has a centering point at its end facing in said drilling direction, through which said rotational axis extends.

7. The drill bit according to any one of claims 1 to 6, wherein said stop shoulder has a stop surface directed perpendicular to said rotational axis and a point in said drilling direction.

8. The drill bit according to any one of claims 1 to 7, wherein said shank has a fixing section, in particular an insertion end, at its end facing in a direction opposite to said drilling direction for temporary fixation to a hand-held drilling machine.

9. A method for fastening a fastening element to a workpiece, comprising: - providing a workpiece having a cover layer - A step of providing a drill bit according to any one of claims 1 to 8, - A step of drilling a blind hole in the workpiece through the cover layer with the drill bit, wherein the first shank section of the drill bit increases in size in a direction opposite to the drilling direction, a step of generating a hole in the cover layer, - A step of providing a fastening element having a sealing element, and - A step of pressing the fastening element into the blind hole, wherein the sealing element is pressed against the hole in the cover layer A method comprising.

10. The method according to claim 9, wherein pressing the fastening element into the blind hole includes screwing the fastening element into the blind hole.

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