JP2009142963A - Twist drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a twist drill which can be adapted to a highly hard steel by minimizing discontinuity between rake faces 12, 13, avoiding easy occurrence of scratch during cutting to prevent the chipping of a thinning cutting blade 10 and a main cutting blade 11, and producing the cutting force of the thinning cutting blade 10 and the main cutting blade 11 in the same direction, if possible, to improve the cutting capability. <P>SOLUTION: In the twist drill, the rake angle of the rake face formed ranging from the linear thinning cutting blade 10 to the side of a spiral main chip discharge groove 4 and the rake angle of the rake face formed ranging from the linear main cutting blade 11 to the side of the spiral main chip discharge groove 4 are each set to be a fixed angle (0°), and the rake faces 12, 13 cross each other at a boundary edge 15 extending from a boundary angle portion 14 between the linear thinning cutting blade 10 and the linear main cutting blade 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement in a twist drill having a thinning cutting edge extending from a chisel edge and a main cutting edge extending from the thinning cutting edge.

In the conventional twist drill disclosed in the following Patent Document 1, as shown in FIG. 3, both the cutting end portions 3 in which the spiral main chip discharge grooves 4 formed in the drill body are opened, A thinning cutting edge 10 that is formed by a thinning portion 9 that has been shaved off from the core and extends from the chisel edge 2a, and a main cutting edge 11 that extends from the thinning cutting edge 10 are provided.
Japanese Patent Laid-Open No. 7-112311

  In the said patent document 1, since the boundary part between the thinning cutting edge 10 and the main cutting edge 11 is rounded, the rake surface formed from this thinning cutting edge 10 to the spiral main chip discharge groove 4 side And the rake face of the rounded boundary portion connecting the rake face formed from the main cutting edge 11 to the spiral main chip discharge groove 4 side, the rake angle of the rake face of the thinning cutting edge 10 and the main cutting edge 11 A large number of rake angles different from the rake angle of the rake face are generated, and these rake faces are discontinuous with each other, so that a catching phenomenon is likely to occur during cutting, and the thinning cutting edge 10 and the main cutting edge 11 are damaged. There was a fear. In addition, since there are many rake faces having different rake angles, the direction of the cutting force generated by the thinning cutting edge 10 and the main cutting edge 11 is easily dispersed, which causes a reduction in cutting ability.

  This invention improves the cutting edge of the twist drill, eliminates the discontinuity of the rake face as much as possible, makes it difficult to cause a catching phenomenon at the time of cutting, and prevents the thinning cutting edge and the main cutting edge from being damaged, The purpose is to increase the cutting ability by making the cutting forces generated by the thinning cutting edge and the main cutting edge work in the same direction as much as possible.

The present invention will be described with reference to the reference numerals of the drawings (FIGS.
The twist drill according to the invention of claim 1 is configured as follows.
On the outer periphery of the chisel portion 2 formed on the rotation center line 1 a of the drill body 1 at the tip portion of the drill body 1, a plurality of cutting end portions 3 having cutting edges 7 are opened adjacent to the cutting end portion 3. A plurality of spiral main chip discharge grooves 4 are alternately arranged in the rotation direction X of the drill body 1. The cutting edge 7 extending from the chisel portion 2 to the outer peripheral portion 6 side of the cutting end portion 3 is provided on the end edge 5a on the rotation direction XF side among the end edges 5a, 5b on both sides in the rotation direction X of each cutting end portion 3. The tip cutting edge angle θ is formed. Each cutting end 3 is formed with a flank 8 having a clearance angle α from the cutting edge 7 to the opposite XR side with respect to the rotational direction XF, and rake surfaces 12 and 13 having rake angles β12 and β13 are formed on the cutting edge 3. It forms from the blade 7 to the spiral main chip discharge groove 4 side. Each of the cutting edges 7 is formed by a thinning portion 9 obtained by scraping the core thickness T of the chisel portion 2 and extends linearly from the chisel edge 2a, and the thinning cutting edge 10 extends from the cutting end portion 3 to the cutting end portion 3. And a main cutting edge 11 extending linearly to the outer peripheral portion 6. The rake angle β12 of the rake face 12 formed from the linear thinning cutting edge 10 toward the spiral main chip discharge groove 4 is set to a constant angle over the entire extending direction of the linear thinning cutting edge 10, and the straight line The rake angle β13 of the rake face 13 formed from the main main cutting edge 11 to the spiral main chip discharge groove 4 side is set to a constant angle over the entire extending direction of the linear main cutting edge 11, and this linear thinning cutting is performed. These rake surfaces 12 and 13 intersect each other at a boundary edge 15 extending from a boundary corner portion 14 between the blade 10 and the linear main cutting edge 11.

  In the invention of claim 2 based on the invention of claim 1, the rake angle β12 of the rake face 12 of the linear thinning cutting edge 10 and the rake angle β13 of the rake face 13 of the linear main cutting edge 11 are Are set at equal angles.

  In the invention of claim 3 premised on the invention of claim 1, the rake angle β12 of the rake face 12 of the linear thinning cutting edge 10 and the rake angle β13 of the rake face 13 of the linear main cutting edge 11 are Are set at different angles.

  In the invention of claim 4 based on the invention of claim 2 or claim 3, the rake angle β12 of the rake face 12 of the linear thinning cutting edge 10 and the rake face 13 of the linear main cutting edge 11 are determined. Of the rake angle β13, at least one of the rake angles β12 and β13 is set to 0 degrees.

  In the invention of claim 5 based on the invention of any one of claims 1 to 4, a pair of the cutting end 3 and the spiral main chip discharge groove 4 are provided.

  In the twist drill, the discontinuity between the rake faces 12 and 13 can be minimized in the twist drill, and it is difficult to cause a catching phenomenon at the time of cutting. The cutting ability can be enhanced by making the cutting forces generated by the thinning cutting edge 10 and the main cutting edge 11 work in the same direction as much as possible. Therefore, the present invention is suitable for a twist drill for high hardness steel.

Hereinafter, a twist drill according to an embodiment of the present invention will be described with reference to FIGS.
A pair of cutting ends 3 and a pair of spirals opened adjacent to the cutting end 3 on the outer periphery of the chisel portion 2 formed on the rotation center line 1 a of the drill body 1 at the tip of the drill body 1. The main chip discharge grooves 4 are alternately arranged in the rotation direction X of the drill body 1. A cutting edge 7 extending from the chisel portion 2 to the outer peripheral portion 6 side of the cutting end portion 3 is provided at an end edge 5a on the rotation direction XF side of the edge portions 5a and 5b on both sides in the rotation direction X of each cutting end portion 3. The tip cutting edge angle θ is formed. A flank 8 having a clearance angle α is formed on each cutting end 3 from the cutting edge 7 to the opposite XR side with respect to the rotational direction XF.

  Each cutting edge 7 includes a thinning cutting edge 10 that is formed by a thinning part 9 in which the core thickness T of the chisel part 2 is shaved off and extends linearly from the chisel edge 2a, and an outer periphery of the cutting end 3 from the thinning cutting edge 10 And a main cutting edge 11 extending linearly to the portion 6. The rake face 12 formed over the entire extending direction of the linear thinning cutting edge 10 from the linear thinning cutting edge 10 to the spiral main chip discharge groove 4 side, and the linear main cutting edge 11 to the spiral main cutting edge. The rake face 13 formed over the entire extending direction of the linear main cutting edge 11 toward the chip discharge groove 4 side is a boundary angle portion between the linear thinning cutting edge 10 and the linear main cutting edge 11. 14 cross each other at a boundary edge 15 extending linearly from 14. The rake angles β12 and β13 of these rake faces 12 and 13 are both set to 0 degrees.

  In the embodiment described above, the rake angle β12 of the rake face 12 of the linear thinning cutting edge 10 and the rake angle β13 of the rake face 13 of the linear main cutting edge 11 are both set to 0 degrees. The rake angles β12 and β13 are both set to, for example, plus 15 to 20 degrees or minus 15 to 20 degrees, or one of these rake angles β12 and β13 is set to plus 15 to 20 degrees or minus 15 to 20 degrees. It may be set to 0 degrees. In general, the rake angle β12 is set smaller than the rake angle β13.

  In the present embodiment, there are only two types of rake angle β12 of the rake face 12 of the linear thinning cutting edge 10 and the rake angle β13 of the rake face 13 of the linear main cutting edge 11, and therefore the linear thinning cutting edge 10 Except for the boundary edge 15 extending from the boundary corner 14 between the straight main cutting edge 11 and the straight main cutting edge 11, discontinuity between the rake faces 12 and 13 is eliminated as much as possible, and the thinning cutting edge is less likely to be caught during cutting. 10 and the main cutting edge 11 can be prevented from being lost. Further, since there are only two types of cutting force directions generated by the thinning cutting edge 10 and the cutting force directions generated by the main cutting edge 11, the cutting force generated by the thinning cutting edge 10 and the cutting force generated by the main cutting edge 11. Each work in the same direction and can increase cutting ability.

  Note that three or more of the cutting end portions 3 and the main chip discharge grooves 4 may be alternately provided.

(A) is a top view which shows the front-end | tip part of a drill main body in the twist drill concerning this embodiment, (b) is a partial front view similarly. (A) is a fragmentary sectional view of the thinning cutting edge extended from a chisel edge in the front-end | tip part of this drill main body, (b) is a fragmentary sectional view of the main cutting edge extended from this thinning cutting edge. It is a top view which shows the front-end | tip part of a drill main body in the conventional twist drill.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Drill main body, 1a ... Rotation center line of drill main body, 2 ... Chisel part, 2a ... Chisel edge, 3 ... Cutting edge part, 4 ... Spiral main chip discharge groove, 5a ... Edge of rotation direction side, 6 ... Cutting 7 ... Cutting edge, 8 ... Flank, 9 ... Thinning part, 10 ... Thinning cutting edge, 11 ... Main cutting edge, 12 ... Rake face of thinning cutting edge, 13 ... Rake face of main cutting edge , 14 ... boundary angle part, 15 ... boundary edge, X ... rotation direction of the drill body, XF ... rotation direction, XR ... opposite to the rotation direction, θ ... tip edge angle, α ... clearance angle, T ... chisel part Heart thickness, β12 ... rake angle, β13 ... rake angle.

Claims (5)

A plurality of cutting end portions having cutting edges and a plurality of spiral main chip discharge grooves opened adjacent to the cutting end portions on the outer periphery of the chisel portion formed on the rotation center line of the drill body at the tip end portion of the drill body Are alternately arranged in the rotation direction of the drill body, and the cutting edge extending from the chisel portion to the outer peripheral portion side of the cutting end portion is provided on the rotation direction side edge of the respective cutting end portions on both sides in the rotation direction. The cutting edge is formed to have a cutting edge angle, and a flank face having a clearance angle is formed at each cutting end from the cutting edge to the opposite side to the rotational direction, and a rake face having a rake angle is formed on the cutting edge. In the twist drill formed from the spiral main chip discharge groove side,
Each of the cutting edges is formed by a thinning portion obtained by cutting off the thickness of the chisel portion and extends linearly from the chisel edge, and a main portion extending linearly from the thinning cutting edge to the outer peripheral portion of the cutting end portion. Having a cutting edge,
The rake angle of the rake face formed from the straight thinning cutting edge to the spiral main chip discharge groove side is set to a constant angle over the entire extending direction of the linear thinning cutting edge. The rake angle of the rake face formed on the spiral main chip discharge groove side is set to a constant angle over the entire extending direction of the linear main cutting edge, and the space between the linear thinning cutting edge and the linear main cutting edge is set. A twist drill characterized in that these rake faces intersect each other at a boundary edge extending from the boundary corner of the shaft. 2. The twist drill according to claim 1, wherein the rake angle of the rake face of the linear thinning cutting edge and the rake angle of the rake face of the linear main cutting edge are set to be equal to each other. 2. The twist drill according to claim 1, wherein the rake angle of the rake face of the linear thinning cutting edge and the rake angle of the rake face of the linear main cutting edge are set at different angles. The rake angle of at least one of the rake angle of the rake face of the linear thinning cutting edge and the rake face of the linear main cutting edge is set to 0 degrees. The twist drill according to claim 2 or 3, wherein: The twist drill according to any one of claims 1 to 4, wherein a pair of the cutting end portion and the spiral main chip discharge groove are provided.

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