JP2007229899A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill capable of preventing a scratch mark from occurring around the entry of a machined hole by the chips generated when the drill bites the workpiece. <P>SOLUTION: In the drill, a chip discharge groove 20 extending toward the rear end side is formed on the outer periphery of a cutting blade part provided on the tip end side of a drill body 10 rotating around the axis line O, and a blade is formed at a crossing ridgeline part between a wall surface 21 toward the front side of the drill rotational direction T of the chip discharge groove 20 and the tip end flank of the cutting blade part. The groove width ratio W1/W2 in a cross section orthogonal to the direction of the axis line O is set to be within 0.3 to 0.6, and the curvature radius R of a groove bottom part 22 of the chip discharge groove 20 is set to be within the range of 0.1×D to 0.25×D with respect to the outside diameter D of the drill. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a drill used for drilling for forming a processed hole in a workpiece.

Conventionally, as such a drill, a cutting edge portion is formed on the front end side of a drill body rotated about an axis, and a pair of chip discharge grooves extending toward the rear end side are formed on the outer periphery of the cutting blade portion. A drill is known in which cutting edges are formed at the intersection ridgeline between the wall surface of the chip discharge groove facing the front side of the drill rotation direction and the tip flank of the cutting edge.
In such a drill, the drill body is rotated around the axis and fed in the axial direction, and pressed against the material to be cut, so that the material to be cut is cut with a cutting blade to have a predetermined inner diameter. A hole is formed.

In the case of cutting with a drill having such a configuration, if chips generated during cutting accumulate inside the processing hole, the cutting resistance increases due to the chips, and the drill breaks, or the chips become cutting edges. It has been known that various troubles occur such as the fact that welding cannot be performed due to welding, and the inner wall surface of the processing hole is damaged by chips.
Therefore, in the conventional drill, in order to promote the chip discharge from the processing hole, the chip width W1 of the chip discharge groove formed on the outer peripheral surface of the cutting edge portion is increased, and the chip discharge groove in the cross section orthogonal to the axis is obtained. The ratio of the groove width W1 to the width W2 of the portion other than the chip discharge groove, that is, the groove width ratio W1 / W2 is increased. For example, in the drill disclosed in Patent Document 1, the groove width ratio W1 / W2 Is 0.9 to 1.3.
Japanese Patent Laid-Open No. 10-76414

  However, in the conventional drill having such a large groove width ratio, the chips when the drill bites into the workpiece tend to be long without being divided, and this long chip rotates with the drill and is processed. Scratch marks may occur around the hole entrance. In this case, the surface roughness of the workpiece becomes rough due to scratch marks, and when the bolt is tightened into the processed hole, the bolt cannot be sufficiently tightened, or the surface condition of the workpiece is deteriorated. The aesthetics were sometimes impaired. For this reason, it may be necessary to take measures such as polishing the surface of the workpiece after forming the processed hole.

  The present invention has been made in consideration of such circumstances, and provides a drill capable of preventing the generation of scratch marks around the hole entrance due to chips generated when the drill bites on the workpiece. The purpose is to do.

  In order to solve this problem, according to the present invention, a chip discharge groove extending toward the rear end side is formed on the outer periphery of a cutting edge portion provided on the front end side of a drill body rotated about an axis, and the chip In a drill in which a cutting edge is formed at a crossing ridge line portion between a wall surface facing the front side in the drill rotation direction of the discharge groove and a tip flank surface of the cutting edge portion, a groove width ratio W1 / W2 in a cross section orthogonal to the axial direction is , 0.3 to 0.6, and the curvature radius R of the bottom of the chip discharge groove is 0.1 × D to 0.25 × D with respect to the drill outer diameter D. It is characterized by being set within the range.

  In the drill having this configuration, the groove width ratio W1 / W2 is as small as 0.6 or less, and the curvature radius R of the bottom surface of the chip discharge groove, that is, the wall surface portion of the chip discharge groove facing the outside in the radial direction of the drill body is small. Since the outer diameter D of the drill is reduced to 0.25 × D or less, the chips guided into the chip discharge groove are curled with a small radius of curvature R, and the chips are cut short. be able to. Therefore, it is possible to prevent the chips generated when the drill bites against the workpiece to rotate with the drill while extending for a long time, and it is possible to prevent the generation of scratch marks around the processing hole entrance.

Further, since the chips are divided into short pieces and the groove width ratio W1 / W2 is set to 0.3 or more and the groove width W1 is secured at a minimum, the chips can be discharged to the rear end side of the drill. Occurrence of troubles due to clogging can be prevented. Moreover, since the curvature radius R of the groove bottom is set to 0.1 × D or more, the chips are surely guided to the curvature radius, and the chip can be prevented from clogging and can be satisfactorily cut. .
Furthermore, since the groove width ratio W1 / W2 is small and the rigidity of the drill can be ensured, vibration when the drill is rotated at a high speed can be prevented, and the processed hole can be formed with high accuracy.

  In order to ensure that such an effect is achieved, it is preferable to set the groove width ratio W1 / W2 within a range of 0.4 to 0.5, and to set the radius of curvature R of the groove bottom to 0. It is preferable to set within the range of 15 × D to 0.2 × D.

  Here, by configuring the curvature radius R1 of the wall surface facing the front side in the drill rotation direction of the chip discharge groove and the curvature radius R2 of the wall surface facing the rear side in the drill rotation direction so as to satisfy a relationship of R1> R2. The chip generated by the cutting blade and guided into the chip discharge groove can be forcibly curled on the wall surface facing the rear side in the drill rotation direction, and the chip can be reliably divided into short pieces.

  Furthermore, it is preferable to set the twist angle θ of the chip discharge groove within a range of 15 ° ≦ θ ≦ 35 °. That is, by setting the twist angle θ of the chip discharge groove to 15 ° or more, the discharge of chips generated at the bottom of the processed hole is promoted, and the drilling process can be performed well, and the twist angle θ is set to 35 °. By setting it as the following, the part which notches a drill main body in the cross section orthogonal to an axis line decreases, and the rigidity of a drill main body can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the drill which can prevent that the abrasion traces generate | occur | produce around a process hole entrance with the chip | tip generated when a drill bites a to-be-cut material can be provided.

A drill according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 to 3 show a drill according to an embodiment of the present invention.
As shown in FIG. 1, the drill body 10 of this drill is formed in a substantially cylindrical shape centering on the axis O, and the rear end side (upper side in FIG. 1) of the drill body 10 serves as a rotating shaft of the machine tool. The shank portion 11 is gripped, and the distal end side (lower side in FIG. 1) of the drill body 10 is a cutting blade portion 12.

  On the outer periphery of the cutting edge portion 12, a pair of chip discharge grooves 20, 20 that twist to the rear side in the drill rotation direction T from the front flank 13 toward the rear end side in the axis O direction rotate 180 ° with respect to the axis O. It is formed symmetrically. The chip discharge groove 20 has a wall surface 21 that faces the front side of the drill rotation direction T, a groove bottom portion 22 that faces the outer side of the drill body 10 in the radial direction, and a wall surface 23 that faces the rear side of the drill rotation direction T.

Further, cutting edges 15 and 15 are formed at the intersecting ridge line portions of the wall surfaces 21 and 21 facing the front side of the drill rotation direction T of the chip discharge grooves 20 and 20 and the tip flank 13 respectively.
Here, at the front end side of the wall surface 21 facing the front side of the drill rotation direction T of the chip discharge groove 20, the drill rotation direction T is connected to the concave curved surface 21A recessed toward the rear side of the drill rotation direction T and the outer peripheral end of the concave curved surface 21A. The cutting edge 15 formed at the intersecting ridge line portion of the wall surface 21 facing the front side of the drill rotation direction T and the tip flank 13 is formed by a convex curved surface 21B that is convex toward the front side. While forming a concave curve shape that is recessed toward the rear side in the rotational direction T, the outer peripheral end portion has a convex curve shape that protrudes toward the front side in the drill rotational direction T. Here, in the present embodiment, the radial rake angle at the outer peripheral end of the cutting edge 15 is set to −8 °, and the radial rake angle at the outer peripheral end portion of the chip discharge groove 20 is set to approximately 0 °.

  As shown in FIG. 2, the tip flank 13 of the cutting edge 12 has a first cutting edge 15, 15 formed on the ridge line portion on the front side in the drill rotation direction T when the chip discharge grooves 20, 20 intersect. The flank faces 13A, 13A and the second flank faces 13B, 13B connected to the first flank face 13A, 13A on the rear side in the drill rotation direction T have a multi-step surface shape. Is provided with a relief that increases in a multi-step manner as it goes backward in the drill rotation direction T. In the present embodiment, the clearance angle formed by the first flank 13A is 7 °, and the clearance angle formed by the second flank 13B is 25 °.

Further, the tip flank 13 is inclined so as to gradually go to the rear end side of the cutting edge portion 12 as it goes outward in the radial direction of the drill body 10, and a predetermined tip angle α is given to the cutting edges 15, 15. It has come to be. In the present embodiment, the tip angle α is set to α = 135 °.
Further, the cutting edge portion 12 is provided with a back taper so that the outer diameter gradually becomes smaller toward the rear end side of the cutting edge portion 12, and in this embodiment, the back taper amount is 0.3 / 100 to 0.35 / 100.

Further, at the tip of the cutting edge portion 12, the groove bottom portion 22 of the chip discharge groove 20, the wall surface 23 facing the rear side in the drill rotation direction T, and the tip flank 13 (first flank 13A and second flank 13B) intersect. The thinning portion 16 is formed so as to cut out the ridge line portion toward the inner side of the chip discharge groove 20 as it crosses the axis O and moves toward the rear end side of the cutting edge portion 12.
Therefore, on the inner peripheral end side of the cutting edge 15, it is connected to a thinning cutting edge 17 that is formed at the intersecting ridge line portion of the thinning portion 16 and the first flank 13 A and extends linearly toward the axis O. .

Here, the outer peripheral surface excluding the pair of chip discharge grooves 20, 20 in the cutting edge part 12, that is, the land part 30 in this drill, in the cross section orthogonal to the axis O, as shown in FIG. A margin part 31 having a substantially arc shape centering on the axis O intersecting with the outer peripheral side ridge line part of the wall surface 21 facing the front side of the drill rotation direction T, and being connected to the drill rotation direction T rear side of the margin part 31, A second picking surface 32 having a substantially arc shape centering on an axis O having an outer diameter smaller by one step than an arc formed by the margin portion 31, and the rear end of the second picking surface 32 in the drill rotation direction T That is, the outer peripheral end portion of the wall surface facing the drill rotation direction T rear side of the chip discharge groove 20 is the heel portion 33.
Further, like the chip discharge groove 20, the margin portion 31 and the second picking surface 32 are arranged on the rear side in the drill rotation direction T from the portion intersecting the tip flank 13 toward the rear end side in the axis O direction. It is formed to be twisted.

  In the cutting edge portion 12, as shown in FIG. 3, the groove width W <b> 1 of the chip discharge groove 20 is smaller than the land width W <b> 2 of the land portion 30, specifically, orthogonal to the axis O. The groove width ratio W1 / W2, which is the ratio of the groove width W1 of the chip discharge groove 20 and the land width W2 of the land portion 30 in the cross section, is set within a range of 0.3 ≦ W1 / W2 ≦ 0.6, and more Preferably, it is set within the range of 0.4 ≦ W1 / W2 ≦ 0.5. In the present embodiment, the groove width ratio W1 / W2 = 0.48.

Further, as described above, the chip discharge groove 20 has a wall surface 21 facing the front side in the drill rotation direction T, a groove bottom portion 22 facing the outer side in the radial direction of the drill body, and a wall surface 23 facing the rear side in the drill rotation direction T. In the cross section perpendicular to the axis O, the radius of curvature R of the concave curve formed by the groove bottom 22 is set within the range of 0.1 × D ≦ R ≦ 0.25 × D with respect to the drill outer diameter D. More preferably, 0.15 × D ≦ R ≦ 0.2 × D is set. In the present embodiment, the radius of curvature R is 0.15 × D.
Further, in the cross section orthogonal to the axis O, the curvature radius R1 of the concave curve formed by the wall surface 21 facing the front side of the drill rotation direction T is smaller than the curvature radius R2 of the concave curve formed by the wall surface 23 facing the rear side of the drill rotation direction T. Thus, a relationship of R1> R2 is established.

  Further, the twist angle of the chip discharge groove 20, that is, the angle θ formed by the axis O and the center line of the chip discharge groove 20 is set within a range of 15 ° ≦ θ ≦ 35 °, and more preferably 20 ° ≦ θ. It is set within a range of ≦ 30 °. In the present embodiment, the twist angle θ is 25 °.

  Further, in the present embodiment, the surface of the cutting edge portion 12 in the drill body 10, that is, the surface of the land portion 30 that is the outer peripheral surface of the cutting blade portion 12, the tip flank 13, the chip discharge groove 20 and the thinning portion 16. On the other hand, a hard film such as TiN, TiCN, or TiAlN is coated.

  In the drill configured as described above, the shank portion 11 formed at the rear end of the drill body 10 is gripped by the rotating shaft of the machine tool and rotated around the axis O, and at the front end side in the axis O direction. It is sent toward and pressed against the material to be cut to form a processed hole having a predetermined inner diameter in the material to be cut. Moreover, the drill of this embodiment is used when forming a through hole in a flange portion in which, for example, the plate thickness t is t = 1 × D with respect to the drill outer diameter D, as the processing hole, The hole depth L of the processed hole is L = 1 × D.

  In the drill having this configuration, the groove width ratio W1 / W2 is set to 0.5, the groove width W1 of the chip discharge groove 20 is reduced, and the radius of curvature R of the groove bottom portion 22 of the chip discharge groove 20 is outside the drill. Since the diameter D is reduced to 0.15 × D, the chips generated by the cutting blade 15 and guided into the chip discharge groove 20 are curled with a small radius of curvature R formed by the groove bottom 22. It is possible to cut the chips and shorten them. Therefore, the length of the chips generated when the drill bites against the workpiece can be shortened to prevent the chips from rotating with the drill, and the generation of scratch marks around the processing hole entrance can be prevented.

Further, since the chip is divided into short pieces and the groove width ratio W1 / W2 is set to 0.5 and the groove width W1 of the chip discharge groove 20 is secured, the chips are passed through the chip discharge groove 20 to the rear end side of the drill. It can discharge | emit and generation | occurrence | production of the trouble resulting from chip clogging can be prevented. Further, since the radius of curvature R of the groove bottom portion 22 is 0.15 × D, the chips are guided to the groove bottom portion 22 to be bent reliably, and the chips are prevented from being clogged without being bent. Can be cut well. In this embodiment, since the hole depth L of the processed hole is L = 1 × D with respect to the drill outer diameter D, the distance that the chip passes through the chip discharge groove is short, and chip clogging occurs. There is little possibility to do.
Furthermore, since the groove width ratio W1 / W2 is as small as 0.5 and the rigidity of the drill is ensured, the occurrence of vibration when the drill is rotated at high speed can be prevented, and the processed hole can be formed with high dimensional accuracy. it can.

  Furthermore, the curvature radius R1 of the wall surface 21 facing the drill rotation direction T front side of the chip discharge groove 20 is R1> R2 with respect to the curvature radius R2 of the wall surface 23 facing the drill rotation direction T rear side of the chip discharge groove 20. Since it is configured to have a relationship, the chips generated by the cutting blade 15 can be forcibly curled on the wall surface 23 facing the rear side in the drill rotation direction T of the chip discharge groove 20, and the chips can be reliably shortened. Can be divided.

  Furthermore, since the twist angle θ of the chip discharge groove 20 is set to θ = 25 °, the chips generated at the bottom of the processed hole can be reliably discharged to the rear end side of the drill and the drilling process can be performed satisfactorily. In addition, the portion of the drill body 10 that is notched in the cross section orthogonal to the axis O is reduced, the rigidity of the drill body 10 can be improved, and the occurrence of vibration when the drill is rotated at high speed is prevented. Can be formed with high dimensional accuracy.

Moreover, in this embodiment, since the outer peripheral end portion of the cutting edge 15 is formed in a convex curve shape and the radial rake angle is −8 °, the sharpness at this outer peripheral end portion is good, The sliding between the inner wall surface of the hole and the outer peripheral end portion of the cutting edge 15 can be prevented, and the work hardening layer can be prevented from being formed around the processing hole.
Further, since the surface of the cutting edge portion 12 in the drill body 10 is coated with a hard film such as TiN, TiCN, or TiAlN, the wear resistance can be improved and the life of the drill can be extended.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, the tip angle, the shape of the cutting edge, and the like are not limited to this embodiment, and can be any shape. However, it is necessary to set the groove width ratio W1 / W2 and the radius of curvature R of the bottom of the chip discharge groove within the scope of the present invention.

Moreover, although this embodiment demonstrated as what coated the ceramic coating, such as TiN, TiCN, TiAlN, on the surface of the cutting-blade part, it is not limited to this, Even if these hard films are not coat | covered Good.
Furthermore, although it demonstrated as a drill which forms the processing hole by which the hole depth L was set to L = 1xD with respect to the drill outer diameter D, it is not limited to this, The deep hole of L> 1xD It may be. However, when the hole depth L of the processed hole is L ≦ 1 × D, it is preferable because the distance that the chips pass through the chip discharge groove is shortened and the possibility of chip clogging is reduced.

Below, the result of the comparative experiment conducted in order to confirm the effect of this invention is demonstrated. In this comparative experiment, using a drill (drill outer diameter 14 mm) with a groove width ratio W1 / W2 and a radius of curvature R of the bottom of the chip discharge groove changed to 7 mm in depth on a carbon steel plate as a workpiece. Then, the chip length and the state of generation of scratches around the hole entrance were evaluated. Moreover, the expansion allowance at the processing hole inlet and the hole outlet, that is, the difference between the inner diameter of the hole and the outer diameter D of the drill was measured. The cutting conditions were a cutting speed of 73 m / min and a feed speed of 0.23 mm / rev.
The experimental results are shown in Tables 1 and 2.

As shown in Table 1, in Comparative Example 1 where the groove width ratio W1 / W2 is large and the curvature radius R of the groove bottom is large, the chip length is as long as 90 mm, and large scratch marks are generated around the hole entrance. Was confirmed. In Comparative Examples 2 and 3 in which the groove width ratio W1 / W2 and the radius of curvature R are relatively small, the chip length is 70 mm, and scratch marks are generated around the hole entrance. Thereby, the surface roughness in the vicinity of the machining hole of the workpiece is increased.
On the other hand, according to the example of the present invention, the chip length is 20 mm, which is significantly shorter than those of Comparative Examples 1 to 3, and no scratch marks are generated around the machining hole entrance. The surface roughness near the machining hole is also small.

Further, as shown in Table 2, in Comparative Examples 1 to 3, it was confirmed that the expansion allowance of the hole was large, and the deflection when the drill was rotated at a high speed was increased. This is because the chip discharge groove has a large groove width and lacks drill rigidity.
On the other hand, in the example of the present invention, it was confirmed that the expansion allowance of the hole was kept small, and the runout when the drill was rotated at high speed was small.
From this experimental result, by setting the groove width ratio and the curvature radius R of the groove bottom of the chip discharge groove within the range of the present invention, it is possible to reliably suppress the generation of scratch marks and to form the processed hole with high dimensional accuracy. It was confirmed that it was possible.

It is a side view of the drill which is embodiment of this invention. It is a X direction arrow line view in FIG. It is YY sectional drawing in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drill main body 12 Cutting edge part 13 Tip flank 15 Cutting edge 20 Chip discharge groove 21 Wall surface 22 which faces the drill rotation direction front side Groove bottom part 23 Wall surface which faces the drill rotation direction rear side

Claims (3)

A chip discharge groove extending toward the rear end side is formed on the outer periphery of the cutting edge portion provided on the tip side of the drill body rotated about the axis, and a wall surface facing the front side in the drill rotation direction of the chip discharge groove and In the drill in which the cutting edge is formed in the crossing ridge line part with the tip flank of the cutting edge part,
The groove width ratio W1 / W2 in the cross section orthogonal to the axial direction is set within a range of 0.3 to 0.6,
The drill has a radius of curvature R at the bottom of the chip discharge groove set within a range of 0.1 × D to 0.25 × D with respect to the outer diameter D of the drill.   The curvature radius R1 of the wall surface facing the drill rotation direction front side of the chip discharge groove and the curvature radius R2 of the wall surface facing the drill rotation direction rear side have a relationship of R1> R2. The drill according to 1.   The drill according to claim 1 or 2, wherein a twist angle θ of the chip discharge groove is set in a range of 15 ° ≤ θ ≤ 35 °.

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