Drill bit

Abstract

A drill bit for a drill includes a body clearance extending helically along the drill bit, a margin also extending helically along the drill bit, adjacent to and projecting radially beyond the body clearance, and a flank at which the body clearance and the margin terminate at a tip of the drill bit. The margin has a variable width along its helical extension.

Claims

1. A drill bit for a drill, comprising: a body clearance extending helically along the drill bit; a margin also extending helically along the drill bit, adjacent to and projecting radially beyond the body clearance; and a flank at which the body clearance and the margin terminate at a tip region of the drill bit, wherein the margin has a variable width along its helical extension.

2. The drill bit according to claim 1, wherein the drill bit is a twist drill bit.

3. The drill bit according to claim 1, wherein the drill is an exchangeable tip drill, and wherein the drill bit is a tip component for the exchangeable tip drill.

4. The drill bit according to claim 1, wherein the variable width is given by one or more locally formed contact areas or by a wave along the helical extension of the margin.

5. The drill bit according to claim 4, wherein at least one local contact area is adjacent to the flank.

6. The drill bit according to claim 4, wherein at least one of the locally formed contact areas has a contact surface that substantially conforms to one of the following shapes: a triangle, a trapezoid.

7. The drill bit according to claim 2, wherein the variable width at any location along the twist drill bit in an azimuthal direction is at most one of the following: one half of a corresponding width of the body clearance, a quarter of a circumference of the twist drill bit.

8. The drill bit according to claim 2, wherein the variable width is configured to suppress a vibration of the twist drill bit.

9. A method of manufacturing a drill bit from a drill bit blank, comprising the following steps: providing the drill bit blank, wherein the drill bit blank has a land between two flutes, and the land extends helically along the drill bit blank; abrading a surface of the land so as to form a body clearance extending helically along the drill bit; thereby variably exempting one or more regions of the surface of the land so as to form a margin, the margin extending helically along the drill bit and having a variable width along its helical extension.

10. The method according to claim 9, wherein the exempting comprises at least one of the following steps: skipping a part of the surface of the land in order to form one or more local contact areas, changing an abrading direction in order to exempt a part of the surface of the land to form a local contact area, regrinding so as to limit the variable width at any location along the drill bit in an azimuthal direction to at most one-half of a corresponding width of the body clearance or at most one-fourth of a circumference of the drill bit.

11. The method according to claim 9, wherein the method further comprises grinding a tip of the drill bit blank so as to form a local contact area adjacent to a flank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The embodiments of the present invention will be better understood by means of the following detailed description and accompanying drawings of the various embodiments, which, however, should not be construed as limiting the disclosure to the specific embodiments, but are intended for explanation and understanding only.

[0051] FIG. 1 shows an embodiment of a twist drill bit.

[0052] FIG. 2 shows a further embodiment of the twist drill bit.

[0053] FIG. 3 shows images of a design of a local contact area in a comparison with a conventional drill.

[0054] FIG. 4 illustrates results of using an embodiment of the twist drill bit, compared to results by a conventional drill.

[0055] FIG. 5 illustrates further results of using the two drills, based on the holes from FIG. 4.

[0056] FIG. 6 shows steps of a method for manufacturing a twist drill bit.

[0057] FIG. 7 shows a further embodiment of a drill bit, wherein the drill bit is a tip component for an exchangeable tip drill.

[0058] FIG. 8 shows a conventional drill.

[0059] FIG. 9 shows a conventional drill bit of an exchangeable tip drill with a conventional tip component.

DETAILED DESCRIPTION

[0060] FIG. 1 shows an embodiment of a twist drill bit 100, with a body clearance 110 extending helically along the twist drill bit 100, and a margin 120 also extending helically along the twist drill bit 100, adjacent to and extending radially beyond the body clearance 110. The twist drill bit 100 furthermore has a flank 130 at which the body clearance 110 and the margin 120 terminate at a tip 105 of the twist drill bit 100. The margin 120 has a variable width B along its helical extension. In particular, the variable width B in this embodiment is given by a locally formed contact area 123. The local contact area 123 is adjacent to the flank 130 and has a substantially triangular contact surface. A surface of the margin 120 and the contact surface of the local contact area 123 together form a common surface. In particular, points on this surface located at the same axial position have an equal radial distance from a longitudinal axis A of the twist drill bit 100. This radial distance is maximal at this axial position, i.e. points of the body clearance 110 located at this axial position are not at this maximal radial distance from the longitudinal axis A. The twist drill bit 100 may be tapered in axial extent. Advantageously, a diameter of the twist drill bit 100 decreases from the tip 105 (starting from a nominal diameter) in the direction of the shank. In this way, in particular, friction can be minimized. The local contact area 123 can in particular reduce low-frequency bending vibrations of the twist drill bit 100. For such vibrations, a local maximum of the amplitude is located at the tip 105 of the tool, usually regardless of the tool geometry. Advantageously, therefore, at least one local contact area may be located at the tip of the tool, as shown here.

[0061] FIG. 2 shows a sketch of a further embodiment of the twist drill bit 100. Here, in addition to the first local contact area 123, a further local contact area 125 is formed. Like the local contact area 123, the further local contact area 125 may in particular be formed to suppress vibration of the twist drill bit 100.

[0062] The further local contact area 125 may have a trapezoidal outline. Its position may in particular be optimized to suppress a higher bending vibration mode of the twist drill bit 100. For this purpose, a position of a maximal amplitude of the corresponding vibration mode may be determined as a function of the geometrical and material parameters of the twist drill bit 100. The shape of the contact areas can also be selected for optimal vibration suppression, but also in favor of the simplest possible manufacturing.

[0063] In general, the twist drill bit may have a large number of local contact areas. The contact areas are advantageously placed in the axial direction where maximal vibration amplitudes are to be expected. The corresponding axial positions usually depend on the remaining tool geometry (e.g. on a ratio of the length to the diameter of the twist drill bit 100, on a twist angle, etc.).

[0064] Depending on the geometry and composition of the twist drill bit, it may also be advantageous not to form the contact area 123 at the tip 105 in particular. For example, in order to meet special requirements, the tip may be designed in such a way that a local contact area at this point is of less importance, or unnecessary.

[0065] FIG. 3 shows, in a part (a), a picture of a tip 5 of a conventional drill 1 with a flank 30, a body clearance 10 and a margin 20. In a part (b) of the figure, an embodiment of the presented twist drill bit 100 is shown. This twist drill bit 100 also comprises a flank 130 at the tip 105, and has a body clearance 110 and a margin 120.

[0066] Both the conventional drill 1 and the drill 100 have a diameter of 10 mm. The length of the cutting part (without the shank for clamping) is 142 mm in each case. The longitudinal axes of drills 1, 100 extend horizontally in this figure.

[0067] The margins 20, 120 in part (a) and part (b) each have a width of approximately 0.5 mm at the points indicated by arrows. The width B of the margin 120 of the twist drill bit in part (b) is however variable: In particular, a local contact area 123 is formed which is adjacent to the flank 130 and contributes to the surface of the margin 120 by its contact surface. The local contact area extends over a height H of 1.0 mm in the axial direction. The variable width B is 1.5 mm (in addition to the margin width of 0.5 mm) at its largest extent visible in part (b).

[0068] This design of the margin 120 (and in particular the variable width B) may depend on characteristics of the twist drill bit, such as its length-to-diameter ratio, its material, or a helix or clearance angle. The twist drill bit may furthermore be coated. Usually, these parameters also depend on the material to be machined.

[0069] The local contact area 123 results in particular in suppression of bending vibrations of the twist drill bit during use.

[0070] It is emphasized that the numerical values shown here are only intended to be understood as an example for a tool. Analogous vibration effects, which are reduced by the embodiment shown in part (b), also occur in tools with significantly different dimensions.

[0071] FIG. 4 illustrates results from an application of an embodiment of the twist drill bit made of solid carbide, compared to results by a conventional solid carbide drill in an aluminum bore.

[0072] In a part (a) of the figure, a surface of a drill hole 70 created by a conventional drill is shown. In a part (b) of the figure, a surface of a drill hole 170 produced by a twist drill bit of the type disclosed herein, having a local contact region 123 at the tip 105, is shown.

[0073] In both cases, a pilot hole with a diameter of 4 mm was drilled first. Both drills have a body clearance width of 0.3 mm. The respective drill hole 70, 170 was produced in both cases with a feed rate of 0.375 mm/rev and a cutting speed of 150 m/min, according to manufacturer's specifications of the conventional tool. In each case, one drill hole is shown over a length, or depth, of approx. 110 mm. A mean diameter of the drill holes 70, 170 is approx. 10 mm in both cases. Radial deviations from the mean diameter are shown exaggerated by a factor of 67. In both parts (a), (b) of the figure, a scale in each case represents a gray scale coding for the radius of the associated, essentially cylindrical drill hole surface 70, 170.

[0074] It can be seen that under the above circumstances, the deviations in part (b) of the figure are significantly smaller than in part (a) of the figure. This can be traced back to the suppression of bending vibrations by the contact area 123.

[0075] FIG. 5 illustrates further results of the comparison from FIG. 4. In part (a) of the figure, a cross-section through the drill hole 70 of the conventional drill is shown at a depth of 60 mm; cf. part (a) in FIG. 4. A circle 71 represents an average drill hole cross-section. A contour 75 shows the actual shape of the drill hole 70 at this depth. The course of the contour 75 in the radial direction is shown exaggerated by a factor of 37.

[0076] A target tolerance range 73 of ±10 μm in diameter is marked around the circle 71. The actually measured contour 75 runs in a range 77 that is significantly larger than the targeted tolerance range 73.

[0077] In part (b) of the figure, a cross-section through the borehole of the twist drill bit according to the invention at a depth of 60 mm is shown; cf. part (b) in FIG. 4. The circle 171 here also represents the central drill hole cross-section. A contour 175 shows the actual shape of the drill hole at this depth. Here, the course of contour 175 in radial direction is also shown exaggerated by 37 times. In this case, the actual measured contour 175 runs within the targeted tolerance range 73.

[0078] This figure thus also illustrates how the additional contact area 123 can improve the precision of a drill hole. In embodiment examples, in particular a diameter deviation and a shape deviation (deviation f.sub.K of roundness with the LSC method according to the standard DIN EN ISO 1101 (2014-04)) can each be improved by at least one tolerance grade (IT) according to DIN EN ISO 286-1 (2010-11).

[0079] FIG. 6 shows steps of a method for manufacturing a twist drill bit 100 having a margin 120 of variable width B. A first step comprises providing S110 a twist drill bit blank already having a land between two flutes, the land extending spirally along the twist drill bit blank, or respectively along the twist drill bit 100 to be formed therefrom. A further step comprises abrading S120 a surface of the land so as to form a body clearance 110 extending spirally along the twist drill bit blank, or twist drill bit 100. In this process, the method further comprises variably exempting S130 a portion of the surface of the land so as to form the margin 120, extending spirally along the twist drill bit blank or twist drill bit 100 and having variable width B along its helical extension.

[0080] In particular, the method may also comprise a prior determination of the variable width B. In this process, for example, positions and/or shapes of local contact areas 123, 125 or of shafts can be adapted to positions of maxima of amplitudes of natural vibration modes of the twist drill bit 100.

[0081] The exempting S130 may optionally comprise skipping one or more regions of the surface of the land in order to form one or more local contact regions 123, 125. Alternatively, or additionally, the exempting S130 may also comprise changing an abrading direction to recess a region of the surface of the land in order to form, for example, a local contact region 125 at an axial position away from a tip of the twist drill bit blank or twist drill bit 100. Furthermore, the exempting S130 may also include regrinding so as to limit the variable width B at each position along the twist drill bit 100 in an azimuthal direction to at most one-half of a corresponding width of the body clearance 110, or to at most one-quarter of a circumference of the twist drill bit, at the respective axial position.

[0082] The method may further comprise grinding a tip of the twist drill bit blank to form a local contact area 123 adjacent to a flank 130.

[0083] FIG. 7 shows, as a further embodiment of the drill bit presented herein, a tip component 100 for an exchangeable tip drill 1, FIG. 9.

[0084] A part (a) of this figure shows, for comparison, a conventional tip component 2 for an exchangeable tip drill. The conventional tip component 2 comprises a flank 30 at the tip 5, a body clearance 10 and a margin 20. The margin 20 extends helically along the tip component 2, and has a constant width. The conventional tip component 2 comprises a stem 6 by which the conventional tip component 2 can be mounted on a drill bit of a corresponding exchangeable tip drill.

[0085] A part (b) of this figure shows the tip component 100 which is an embodiment of the drill bit as presented herein. This tip component 100 also comprises a flank 130 at the tip 105, and has a body clearance 110 and a margin 120. The tip component 100 further comprises a stem 106 by which the tip component 100 may be mounted on a drill bit of a corresponding exchangeable tip drill 1, FIG. 9. The margin 120 extends helically along the tip component 100 and has a variable width B. In particular, the variable width B of the tip component 100 is such that a local contact area 123 is formed where the margin 120 adjoins the flank 130. If the drill bit of the exchangeable tip drill 1, FIG. 9 is equipped with the tip component 100, the local contact area 123 results in particular in suppression of bending vibrations of the drill bit during use. Depending on size and further constraints of the tip component 100, further local contact areas may be added to the margin 120 along its helical extent.

[0086] While the present invention has been described with reference to exemplary embodiments, it will be readily apparent to those skilled in the art that the invention is not limited to the disclosed or illustrated embodiments but, on the contrary, is intended to cover numerous other modifications, substitutions, variations and broad equivalent arrangements that are included within the spirit and scope of the following claims.

LIST OF REFERENCE SIGNS

[0087] 1 conventional drill bit

[0088] 2 conventional tip component

[0089] 5 tip

[0090] 6 stem

[0091] 10 body clearance

[0092] 20 margin

[0093] 30 flank

[0094] 70 drill hole

[0095] 71 averaged drill hole cross section

[0096] 73 tolerance range

[0097] 75 drill hole contour

[0098] 77 range of deviations

[0099] 100 drill bit

[0100] 105 tip

[0101] 106 stem

[0102] 110 body clearance

[0103] 120 margin

[0104] 123, 125 contact areas

[0105] 130 flank

[0106] 170 drill hole

[0107] 171 averaged drill hole cross section

[0108] 175 drill hole contour

[0109] A longitudinal axis

[0110] B variable width

[0111] H axial length of an additional contact area

[0112] S110, S120, . . . steps of a method