JP2000271805A - Hole machining tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent chipping of a cutting edge when inserting to a tool holder. SOLUTION: A boring bar 20 is substantially shaped in a bar, and a pair of cutting edge portions 22, 22 are provided on both sides of a shank portion 21 taking a view in a longitudinal direction of the boring bar 20. The shank portion 21 is substantially cylindrical shape, and provided with a step portion 24 at a connection with the cutting edge portion 22 in a part of a circumferential direction to make the outer diameter of a part of the cutting edge portion 22 smaller than the shank portion 21. A cutting edge 26 arranged at a tip of the cutting edge portion 22 is formed so as to slightly tilt to a diametrical direction to take the maximum width of the cutting edge portion 2, and a cutting edge projecting to the most tip outer periphery side is retracted in a diametrically inside more than the shank portion 21. The knife edge of the cutting edge 26 is positioned in the diametrically inside more than the outer peripheral surface of the shank portion 21 within a range 0.05D to 0.25D (D indicates the maximum outer diameter of the shank portion 21).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool such as a boring bar, and more particularly, to a drilling tool having a small diameter used for processing small precision parts.

[0002]

2. Description of the Related Art Conventionally, there is a boring bar as an example of a turning tool as a drilling tool. An example of this type of boring bar is disclosed in Japanese Patent No. 2878430. This boring bar will be described with reference to FIGS. The boring bar 1 shown in FIG. 7 (A) is provided with cutting blades 3 and 3 on both sides of a shank portion 2 having a substantially rod shape, and a cutting blade 4 is provided at the tip of each cutting blade 3 in the radial direction. . The shank portion 2 has a cylindrical shape and has positioning flat portions 5 and 5 formed on opposing outer peripheral surfaces. In addition, the side portion 6 of the shank portion 2 is cut off in a flat shape to form a flat portion 5,
5 and is formed as a flank for the cutting edge 3 (see FIG. 7B). Therefore, the cutting edge 4 a in the radial direction of the cutting blade 4 is positioned to protrude beyond the side surface 6 of the shank portion 2. A rear end 4b of the cutting blade 4 opposite to the cutting edge 4a is cut obliquely. The maximum width d1 of the cutting blade 3 in the radial direction is the maximum width d2 of the shank 2.
(See FIG. 7B).

When the boring bar 1 is used for cutting, one end of the boring bar 1 is inserted into a substantially cylindrical hole-shaped insertion hole 9 of a tool holder 8 shown in FIG. The flat portion 5 of the shank portion 2 is pressed and fixed by the screws 10 and 10 through the screw holes of the tool holder 8. Then, the outer peripheral surface of the tool holder 8 is attached to a machine tool or the like,
The rotating work is cut by the cutting blade 4 to form an inner diameter hole.

[0004]

By the way, in such a boring bar 1 in which the cutting edges 4 and 4 are provided on both sides of the shank portion 2, the maximum width d1 in the radial direction of the cutting edge portion 3 and the shank portion 2 Since the maximum width (maximum diameter) d2 is formed to be the same and the cutting edge 4a of the cutting blade 4 is formed so as to protrude radially outward with respect to the side surface portion 6 of the shank portion 2,
When one end of the boring bar 1 is inserted into the hole 9 of the tool holder 8, there is a disadvantage that the cutting edge 4 a of one of the cutting blades 4 comes into contact with the inner wall of the hole 9 and the cutting edge is likely to be damaged.
In the above-described prior art, a notch for inserting the cutting edge 4a of the cutting blade 4 is provided in the hole 9 of the tool holder 8, but when the boring bar 1 is inserted, the cutting blade 4 and the notch are positioned at a regular angle. However, the disadvantage that the cutting edge is likely to be lost cannot be sufficiently improved, and the machining of the cut portion in the hole 9 is difficult and complicated.

SUMMARY OF THE INVENTION [0005] In view of the above-mentioned problems, an object of the present invention is to provide a drilling tool that is less likely to cause a cutting edge defect when inserted into a tool holder.

[0006]

A drilling tool according to the present invention is a drilling tool having a substantially bar shape and having cutting edges provided on both sides of a holding portion when viewed in the longitudinal direction. The cutting edge located on the outside is located radially inside the holding portion. When using this hole drilling tool for inside diameter drilling, when inserting one end having a cutting edge not used for cutting the hole drilling tool into the hole of the tool holder, the cutting edge of the cutting edge is radially inward from the holding part. As a result, there is no risk of contacting the inner wall of the hole, and the hole can be reliably inserted and fixed in the hole without causing any loss. In addition, when drilling a work material, since the cutting edge of the cutting blade is located radially inward of the holding portion, the inner diameter of the processing hole can be reduced to be equal to or less than the outer diameter of the holding portion.

[0007] When the maximum outer diameter of the holding portion is D, the cutting edge of the cutting blade is 0.05D to 0.2mm from the outer peripheral surface of the holding portion.
It may be located radially inward in the range of 25D. If the radial distance at which the cutting edge of the cutting blade is retracted from the outer peripheral surface of the holding portion is smaller than 0.05D, the position of the cutting edge in the radial direction is substantially the same as the outer peripheral surface of the holding portion and is inserted into the hole of the tool holder. At this time, there is a possibility that the cutting edge comes into contact with the inner wall of the hole portion to cause breakage. If the cutting edge is larger than 0.25D, the outer diameter of the cutting edge portion is reduced, so that the rigidity is reduced and the cutting edge is easily broken during cutting.

[0008] The minimum inner diameter of the machining hole that can be cut by the cutting blade may be smaller than the outer diameter of the holding portion. Even if the outer diameter of the holding portion of the drilling tool is the same as that of the conventional tool, it is possible to drill a smaller diameter hole. Further, in the drilling tool according to the present invention, the cutting edge is connected to the holding portion via the step portion, and is provided at the tip of the cutting edge portion partially smaller in diameter than the holding portion, and is connected to the cutting edge of the cutting edge. The flank may be formed so as to retreat radially inward from the holding portion and the cutting edge in the direction of the holding portion. When drilling a work material, the side flank of the cutting edge is located radially inward from the cutting edge of the cutting blade. Without contacting the surface, the surface roughness of the inner wall of the drilled hole can be maintained in good condition and drilling with high accuracy can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. The same reference numerals are used for the same or similar parts as those of the above-mentioned prior art.
1A is a side view of a boring bar according to an embodiment, FIG. 1B is a cross-sectional view taken along line YY of FIG. 1A, FIG. 2 is a side view of a cutting edge portion of the boring bar, and FIG. 2 is an enlarged sectional view of a portion A, FIG. 4 is an enlarged front view of a boring bar, and FIG. 5 is a partial sectional view of a state where the boring bar is inserted into a tool holder. The boring bar 20 shown in FIGS. 1 to 4 is, for example, a solid type tool for drilling a small-diameter hole made of a material such as cemented carbide, cermet, or ceramic, and has a substantially cylindrical rod shape. And a pair of cutting blades 22, 2 formed on both sides of the center shank 21.
2 and has an outer peripheral surface 31 having a substantially cylindrical peripheral surface shape. The shank portion 21 has a substantially columnar shape, and has a pair of planar positioning surfaces 23 and 23 formed in parallel with each other by cutting off the outer peripheral surface 31 opposite to both sides of the center axis O therebetween. Each positioning surface 23 is basically a shank 2
1 to the tip of the cutting blade 22.

Each of the cutting blades 22, 22 is formed as a rod-shaped shaft having a step portion 24 formed at a connection portion with the shank portion 21 and having an outer diameter partially smaller in the circumferential direction than the shank portion 21. The outer peripheral surface 31 of the distal end side region is partially cut out together with the positioning surface 23 to form a concave curved concave portion 25. A cutting blade 26 is provided on the ridgeline of the tip of the concave portion 25 so as to intersect the longitudinal direction of the boring bar 20 and extend in the radial direction. In a plan view of the cutting blade 26 shown in FIG. 1 (the left cutting blade 26 in FIG. 1), the cutting blade 26 is inclined at a minute angle with respect to a direction orthogonal to the central axis O (for example, 5 ° ± 3 °).
0 ') are arranged and the cutting blade 26 formed in the concave portion 25
In the rake face 27, the ridgeline 28 on the side surface intersecting the cutting blade 26 and the cutting edge 26a located at the outer end of the cutting blade 26 also has a small angle (for example, 5 ° ± 30 °) so that the ridgeline 28 extends outward toward the distal end side with respect to the central axis O. ') It is provided at an angle.
A rear end 26b which is an end opposite to the cutting edge 26a of the cutting blade 26
Is located on the same outer peripheral surface 31 connected to the shank portion 21 and the cutting blade portion 22. In the side views of the cutting blade portion 22 shown in FIGS. 2 and 3, the rake face 27 is a concave portion 25 forming a concave curved surface.
The step 29 is formed in the region on the front end side of which is lower by one step, and the cutting blade 26 and the rake face 27 are positioned higher than the center axis O (see FIG. 4).
Note that the step 29 may not be provided, and in this case, the rake face 27 is formed on a surface that smoothly continues from the cutting blade 26 to the recess 25.

The flank 30 of the cutting blade 26 formed on the tip end surface of the boring bar 20 in the cutting blade portion 22 faces inward from the cutting blade 26 toward the positioning surface 23 that cuts the outer peripheral surface 31 of the cutting blade portion 22. The positive is inclined.
In FIG. 4, a ridge line 28 connected to the cutting blade 26 at a cutting edge 26a.
The side flank 32 is formed by a positive first flank 32A and a second flank 32B in which the flank angle increases stepwise, and the inner wall is formed when the cutting edge portion 22 enters the machining hole during boring. The relief angle of the two-stage positive is set so as not to contact with. Also, as shown in FIG. 4, a first inclined surface 33A connected to the second flank 32A and a second inclined surface 33B connected to the positioning surface 23 are also provided on the shaft portion 33 between the concave portion 25 of the cutting blade portion 22 and the shank portion 21. And the first flank 32A
Is gradually inclined inward from the tip toward the shank portion 21 side and is connected to the first inclined surface 33A so that it does not contact the machined surface during drilling. The second flank 32B, the first inclined surface 33A, and the second inclined surface 33B of the shaft portion 33.
Is connected to the step portion 24, and the outer circumference of this region of the cutting blade portion 22 is smaller in diameter than the outer diameter of the shank portion 21.

As shown in FIG. 1, the cutting blades 26, 26 and the recesses 25, 25 are rotated by 180 ° about the central axis O with respect to the pair of cutting blades 22, 22 located on both sides of the boring bar 20. And both cutting blades 26,
The 26 cutting edges 26a, 26a are oriented in the same circumferential direction, that is, in the steps 24, 24 of the shank portion 21. Therefore, in FIG. 1, the boring bar 20 is rotationally symmetric with respect to a bisector Z of the boring bar 20 orthogonal to the central axis O. 1 and 4, the maximum outer diameter of the shank portion 21 of the boring bar 20 is denoted by D, and the maximum radial width Da of the cutting edge portion 22 is the radial width of the cutting edge 26 in this example. D> Da. And D-Da
= S, the distance difference s is the distance from the outer peripheral surface 31 of the shank portion 21 to the position of the cutting edge 26a of the cutting blade 26 retracted radially inward.

The distance difference s is preferably 0.05D to 0.
Set in the range of 25D. If the distance difference s is smaller than 0.05D, the maximum width Da of the cutting blade 26 becomes substantially the same as the maximum outer diameter D of the shank portion 21, so that when the boring bar 20 is mounted on the tool holder 8, However, there is a drawback that the contact with the inner wall of the hole 9 tends to cause the loss. The distance difference s
Is larger than 0.25D, the rigidity of the cutting edge portion 22 is lower than that of the shank portion 21, and there is a disadvantage that the cutting edge portion 22 is easily broken. In the boring using the ball end mill 20, the minimum inner diameter of the processing hole is equal to the maximum width Da of the cutting blade 26. Therefore, by setting D> Da, the shank 2
In this case, a machined hole having an inner diameter equal to or less than the maximum outer diameter D can be formed. As a numerical example, if D = 2 mm, s = 0.1 to 0.5
mm range.

A tool holder 35 for mounting the boring bar 20 will be described with reference to a partial sectional view shown in FIG. 5. The tool holder 35 is formed, for example, in a substantially cylindrical shape, and is coaxially formed from one end. A hole 36 is formed, and the inside diameter of the hole 36 is slightly smaller than the outside diameter D of the shank 21 of the boring bar 20. Then, the boring bar 20 is moved from one of the cutting blades 22 to the hole 3.
6, the screw 10 is screwed into the screw hole while the positioning surface 23 is opposed to a screw hole (not shown) formed in the outer peripheral surface of the tool holder 35.
Is pressed to fix.

Since the boring bar 20 according to the present embodiment is configured as described above, when performing boring of a workpiece using the boring bar 20, first, a cutting blade 26 not used for cutting is provided. One of the cutting blades 22 is inserted into the hole 36 of the tool holder 35. At that time, the cutting blade 2
6 is brought into contact with the inner wall of the hole 36 by inserting the outer peripheral surface 31 connected to the rear end 26b thereof into the inner wall of the hole 36.
The cutting edge 26a should have a gap of a distance s from the inner wall of the hole 36, so that the cutting edge 26a can be reliably prevented from contacting the inner wall of the hole 36 and can be inserted. When the shank portion 21 enters the hole portion 36, the outer peripheral surface 31 serves as a guide, so that there is no risk of the cutting edge 26 being lost.
After that, the positioning surface 23 may be pressed and fixed to the shank 21 by inserting the screw 10 into the hole 36. Thus, the boring bar 20 can be fixedly held on the machine tool via the tool holder 35.

Then, with respect to the end face of the rotating work,
The cutting edge 26a of the cutting blade 26 protruding from the tool holder 35 of the boring bar 20 is bitten, and the boring bar 20 is pushed into the processing hole 38 while being cut by the cutting blade 26, thereby performing the drilling (see FIG. 4). At this time, since the ridge line 28 connected to the cutting edge 26a of the rake face 27 is inclined outward by a small angle, the side flank 32 of the ridge line 28 also escapes from the bored inner wall, and there is a possibility that the flank 32 may contact the inner wall. Absent.
Further, the inner diameter of the processing hole 38 is in the range of Da to 2 Da in relation to the maximum width Da of the cutting blade 26, and the cutting edge 2
6a. For example, in order to drill a processing hole having the same inner diameter as the outer diameter of the shank portion 21, the radial distance from the rotation center of the work to the cutting edge 26a is D / D.
It may be set to 2. In this case, as shown in FIG. 4, the machining hole 38 of the workpiece is formed at a position shifted from the outer peripheral surface 31 of the shank portion 21 by a distance s in the direction in which the cutting edge 26a is retracted. Therefore, the depth of the processing hole 38 is set to the cutting edge 26a.
Is limited to the length L of the cutting blade portion 22 from the to the step portion 24 of the shank portion 21.

According to the present embodiment as described above,
When the ring bar 20 is inserted into the tool holder 35, the cutting edge 26
There is no danger that 6a may be damaged by contacting the inner wall of the hole 36. Moreover, it is possible to perform boring with an inner diameter smaller than or equal to the outer diameter D of the shank portion 21.

In the above-described embodiment, the cutting edge 26a of the cutting blade 26 is projected outward in the radial direction. However, it is not always necessary to project the cutting edge 26a, and the ridge 28 and the side flank 32 connected to the cutting edge 26a are aligned with the central axis O. Is formed in parallel with the cutting blade 26.
May be set as a maximum width Da having substantially the same dimension as the outer diameter of the cutting blade portion 22. Further, the rear end 26b of the cutting blade 26 opposite to the cutting edge 26a may be rounded as shown in FIG. 6, or may be cut obliquely and chamfered. With this configuration, the rear end portion 26b serves as a guide for insertion into the tool holder 35, and can be inserted without making the cutting blade 26 more reliably contact the inner wall of the hole portion 36. The boring bar 20 constitutes a drilling tool, and the shank 21 constitutes a holding part.

[0019]

As described above, in the drilling tool according to the present invention, since the cutting edge located radially outside the cutting edge is located radially inside the holding portion, one end of the drilling tool is provided. When inserting the part into the hole of the tool holder, the cutting edge of the cutting blade is retracted radially inward from the holding part, so there is no danger of contact with the inner wall of the hole and the inside of the hole is securely formed without any loss. When drilling holes, the cutting edge of the cutting blade is located radially inward of the holding portion, so that the inner diameter of the processing hole can be made smaller than the outer diameter of the holding portion.

When the maximum outer diameter of the holding portion is D, the cutting edge of the cutting edge is 0.05D to 0.2mm from the outer peripheral surface of the holding portion.
Since the blade is positioned radially inward within the range of 25D, the blade edge position is substantially the same as the outer peripheral surface of the holding portion, and when the blade edge is inserted into the hole of the tool holder, the blade edge contacts the inner wall of the hole. There is no risk of chipping, and the outer diameter of the cutting edge portion is reduced, rigidity is reduced, and breakage is not easily caused during cutting.

[Brief description of the drawings]

1A and 1B show a boring bar according to an embodiment of the present invention, wherein FIG. 1A is an overall plan view, and FIG. 1B is a cross-sectional view taken along line YY in FIG.

FIG. 2 is a side view of a cutting edge portion of the boring bar shown in FIG.

FIG. 3 is an enlarged sectional view of a portion A in FIG. 2;

FIG. 4 is a front view of the boring bar.

FIG. 5 is a partial sectional view showing a state in which the boring bar according to the embodiment is mounted on a tool holder.

FIG. 6 is a partial plan view showing a modified example of the cutting edge portion of the boring bar according to the embodiment.

FIG. 7 shows a conventional boring bar,
(A) is an overall plan view, and (B) is a sectional view taken along line XX of FIG. (A).

FIG. 8 is a longitudinal sectional view of a tool holder.

[Explanation of symbols]

 Reference Signs List 20 boring bar 21 shank 22 cutting blade 26 cutting blade 26a cutting edge

Claims (3)

[Claims] 1. A hole drilling tool having a substantially bar shape and having cutting edges provided on both sides of a holding portion when viewed in the longitudinal direction,
A cutting tool, wherein a cutting edge located radially outside the cutting blade is located radially inside the holding portion. 2. When the maximum outer diameter of the holding part is D, the cutting edge of the cutting blade is 0.05D or more from the outer peripheral surface of the holding part.
2. The drilling tool according to claim 1, wherein the drilling tool is located radially inward in a range of 0.25D. 3. The drilling tool according to claim 1, wherein a minimum inner diameter of the drilled hole that can be cut by the cutting blade is equal to or less than a maximum outer diameter of the holding portion.