JPH10156613A - Eddy-shaped thinning drill with chisel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a run-out of riceball shape also obtain good discharge performance of cutting chips even in the case of a web core thickness in relatively large thickness, while avoiding chipping and excessive biting of a cutting edge and leaving a chisel edge. SOLUTION: A pair of cutting edges 14a, 14b are formed in a shape protruded in the drill rotating direction (counter clockwise direction in the drawing) as viewed by a bottom surface, when going toward a side of a drill axial center O form a drill peripheral edge, the cutting edge is made gradually adjacent to this drill axial center O, so that a drill axial center side end part is made further adjacent to the drill axial center O beyond a corner of a chisel edge 16, eddy-shaped thinning 22a, 22b (oblique line part) is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill, and more particularly to an improvement in a thinning shape.

[0002]

2. Description of the Related Art In order to reduce cutting resistance in drilling, S-type, N-type, X-type, and composite types thereof are used as thinning for thinning the web tip at the tip of a drill. I have. Japanese Patent Publication No. 39-16589 proposes a drill provided with an S-shaped cutting edge in order to solve the problem of the occurrence of runout at the start of drilling of a drill provided with a straight chisel edge. Japanese Utility Model Laid-Open Publication No. 48-53679 discloses an intersection between a center side cutting edge and an outer side cutting edge, that is, a corner of a chisel edge formed by so-called X-thinning. A drill in which a corner is rounded with an arc having a predetermined radius of curvature has been proposed. FIG. 4 (a)
Is an example of an S type, (b) is an example of an N type, (c) is an example of a spiral type, and (d) is an example of an X type. Each of the hatched portions 100 and 102 is a thinned surface, and 104 and 106 are a pair. The cutting edges 108 and 110 are flank faces, and 112 is a chisel edge. These thinnings increase the rake angle in the center, shorten the length of the chisel, take a surface on the escape side of the groove, etc., to improve the sharpness in the center, The aim is to improve emissions.

[0003]

However, since the S-type thinning and the N-type thinning still have a straight chisel edge, both ends thereof are alternately the instantaneous rotation centers of the drill and are formed into a triangular or pentagonal tapered shape. There were problems such as rotational vibration, a decrease in processing accuracy such as roundness, and the generation of rifle marks (spiral flaws). Another problem is that drills for high-speed heavy-cutting of difficult-to-cut materials such as tempered steel have a large web core thickness, so the chips that have been cut near the axis have poor discharge properties and are likely to be clogged. Included.

[0004] On the other hand, in the spiral type thinning, a pair of cutting edges are connected at an axis and there is no chisel edge. However, the cutting edge becomes thin near the axis and is apt to be chipped. There has been a problem that vibration occurs and the drill comes off the chuck. In particular, in drills for high-speed heavy cutting of difficult-to-cut materials,
The occurrence of chipping becomes remarkable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to prevent chipping and excessive run-out of a cutting edge while leaving a chisel edge while preventing a run-out of a tapered core. Another object of the present invention is to provide good chip evacuation performance even when the web core thickness is relatively large.

[0006]

In order to achieve the above object, a first aspect of the present invention has a straight chisel edge crossing a drill axis in a bottom view and extends from both corners of the chisel edge to an outer peripheral edge of the drill. A chiseled drill in which a pair of cutting edges are provided symmetrically with respect to a drill axis, wherein the cutting edges have a shape that is convex in a drill rotation direction in a bottom view, and a drill is formed from an outer peripheral edge of the drill. A tom-shaped thinning is performed so that the drill axis is gradually approached toward the axis side and the end of the drill axis side is further approached to the drill axis beyond the corner of the chisel edge. It is characterized by having been given.

A second aspect of the present invention is based on the first aspect, wherein (a) the chisel edge has a diameter of 10% or less of a drill diameter, and (b) the end of the cutting edge on the drill axis side extends from a corner of the chisel edge to the chisel edge. It is characterized in that it is extended at least half the length.

In a third aspect based on the first or second aspect, the cutting edge is formed at a position offset in the drill rotation direction by a predetermined dimension from a straight line passing through the drill axis in a bottom view and substantially parallel to the straight line. The outer peripheral side cutting edge portion, and an arc-shaped inner peripheral side cutting edge portion that is smoothly connected to the inner peripheral side end portion of the outer peripheral side cutting edge portion.

In a fourth aspect based on the first or second aspect, the cutting edge is formed at a position offset in the drill rotation direction by a predetermined dimension from a straight line passing through the drill axis in a bottom view and substantially parallel to the straight line. An outer peripheral side cutting edge portion, and a straight inner peripheral side cutting edge portion obliquely connected to an inner peripheral side end portion of the outer peripheral side cutting edge portion.

A fifth invention is characterized in that, in the third invention or the fourth invention, an end of the cutting edge on the drill axis side projects beyond the straight line to the opposite side.

[0011]

In such a towel-type thinning drill with a chisel, the cutting edge is gradually approached to the drill axis from the outer peripheral edge of the drill toward the drill axis, and the end of the drill axis side is also provided. Because the part is moved closer to the drill axis beyond the corner of the chisel edge, the centrifugal force is obtained by the cutting resistance acting from the corner of the chisel edge to the end of the drill axis, and the presence of the chisel edge Regardless, rice ball-shaped core runout is suppressed well, and excellent processing accuracy can be obtained. In addition, since the thinning is performed to the vicinity of the drill axis and the cutting edge has a shape that is convex in the drill rotation direction, a drill that performs high-speed heavy cutting of difficult-to-cut materials with a relatively thick web core In this case, good chip discharge performance can be obtained. Furthermore, since the chisel edge remains near the drill axis, a suitable cutting edge strength is obtained, chipping is well prevented in combination with suppression of center runout, and excessive cutting edge cutting is also prevented. You.

In the second aspect of the present invention, since the chisel edge is 10% or less of the drill diameter, the cutting resistance caused by the chisel edge is favorably reduced while maintaining the predetermined cutting edge strength and preventing the cutting edge from biting too much. In addition, the runout of the core is more effectively suppressed. In addition, since the end of the cutting edge on the drill axis side extends from the corner of the chisel edge by half or more of the length of the chisel edge, chip evacuation at the center portion is improved, and the cutting of that portion is performed. A suitable centripetal force is obtained by the resistance.

According to the fifth aspect of the present invention, since the end of the cutting edge on the drill axis side projects beyond the straight line passing through the drill axis substantially parallel to the outer peripheral cutting edge, the cutting edge is similarly cut at the center. In addition to improving the dust discharging property, an appropriate centering force can be obtained by the cutting resistance of the portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is suitably applied to, for example, a drill for high-speed heavy cutting having a web core thickness of about 25% to 50% of a drill diameter. In that case, high rigidity that can withstand large cutting resistance is obtained while securing the groove depth required for chip discharge, and the rice ball-shaped core runout is more effectively suppressed.

The length of the chisel edge is desirably 10% or less of the diameter of the drill for preventing runout of the core and reducing the cutting resistance. However, if the length is too short, the strength of the cutting edge is impaired or the bite is too deep. To at least 0.
It is desirable to leave about 5 mm or more.

[0016] The end of the cutting edge on the drill axis side is moved further beyond the corner of the chisel edge to the drill axis, but the end of the cutting edge does not need to be brought closest to the drill axis, and the end of the chisel edge is not required. An intermediate portion between the corner and the corner may be adapted to be closest to the drill axis.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a toe-shaped thinning drill 10 with a chisel according to an embodiment of the present invention (hereinafter simply referred to as a drill 10).
2) is a bottom view as viewed from the tip side, and FIG.
FIG. 3 is a side view showing the tip of the drill 10. This drill 10 is made of tool steel, high speed steel, cemented carbide, cermet,
It is made of a well-known material such as a diamond ultra-high pressure sintered body and has a web core thickness of about 30% of the drill diameter for high-speed heavy cutting of a difficult-to-cut material. 1 and 2, a pair of spirally formed chip discharge grooves 12a and 12b are formed in the conical tip surface of the drill 10 so that the starting end is near the drill axis O in bottom view. A pair of cutting edges 14a and 14b whose ends reach the outer peripheral edge of the drill are formed symmetrically with respect to the drill axis O. In addition, a straight chisel edge 16 that intersects the drill axis O is provided.
The two ends, that is, the corners, are the pair of cutting edges 14a,
14b intersects obliquely.

The pair of cutting edges 14a and 14b are substantially parallel to the straight line S at a position offset from the straight line S passing through the drill axis O by a predetermined dimension in the drill rotation direction (the counterclockwise direction in FIG. 1) when viewed from the bottom. Outer cutting edge portions 18a, 18b formed on the outer peripheral cutting edge portions 18a, 18b,
The inner peripheral edge portion 20a and the inner peripheral edge portion 20b are smoothly connected to the inner peripheral edge of the inner peripheral edge 18b. The inner peripheral side cutting edge portions 20a, 20b are convex in the drill rotation direction when viewed from the bottom by a pair of tom-shaped thinnings 22a, 22b (hatched portions in the figure) symmetrically provided with respect to the drill axis O. It has an arc shape, and is gradually approached to the drill axis O toward the drill axis O side,
The end of the drill axis side is further moved closer to the drill axis O beyond the corner of the chisel edge 16.

Due to the tom-shaped thinnings 22a and 22b, the length of the chisel edge 16 is set to 10% or less of the drill diameter, and in the embodiment, about 6% to 7%.
The ends of the cutting edges 14a, 14b on the drill axis side are か ら of the length of the chisel edge 16 from the corner of the chisel edge 16.
It extends as described above and projects beyond the straight line S to the opposite side. The radius of curvature of the inner peripheral side cutting edge portions 20a and 20b is about 24% or more of the drill diameter, and about 40% in the embodiment.
%, And is smoothly connected to the outer peripheral cutting edges 18a, 18b, and the chisel angle ε, which is the intersection angle between the tangent at the corner of the chisel edge 16 and the chisel edge 16, is about 130 ° or more. In the example, it is about 135 °. In addition, the inner peripheral side cutting edge portion 20
a and 20b are closest to the drill axis O at an intermediate position between the end of the drill axis side beyond the straight line S and the corner of the chisel edge 16, and the end side of the closest side is substantially closer to the drill axis O. Does not function as a cutting edge. At the tip of the drill 10, a flank 24 is formed continuously with the cutting edges 14a and 14b.
a, 24b are provided.

In such a drill 10, the cutting edges 14a and 14b are gradually approached to the drill axis O from the outer peripheral edge of the drill toward the drill axis O, and the end of the drill axis side. Is chisel edge 16
Of the chisel edge 16, the centering force is obtained by the cutting force acting from the corner of the chisel edge 16 to the end of the drill axis, and the presence of the chisel edge 16 Regardless, rice ball-shaped core runout is suppressed well, and excellent processing accuracy can be obtained.

Further, the tomographic thinnings 22a and 22b are provided up to the vicinity of the drill axis O, and the cutting edge 14a is formed.
Since a and 14b have a shape that is convex in the drill rotation direction as a whole, even in the drill 10 for high-speed heavy cutting of a difficult-to-cut material having a relatively thick web core as in the present embodiment,
Good chip evacuation performance is obtained.

Particularly, in this embodiment, the cutting edges 14a, 14b
The end of the drill shaft center side extends from the corner of the chisel edge 16 by half or more of the length of the chisel edge 16 and projects beyond the straight line S to the opposite side. While improving, an appropriate centering force can be obtained by the cutting resistance of that portion.

Further, since the chisel edge 16 remains near the drill axis O, an appropriate cutting edge strength is obtained, chipping is prevented well in combination with the suppression of center runout, and the cutting edge 14a , 14b are prevented from being excessively bitten.

In this embodiment, since the chisel edge 16 is about 6% to 7% of the drill diameter, the chisel edge 16 is formed while preventing the cutting edges 14a and 14b from biting too much while securing a predetermined cutting edge strength. In addition to reducing the cutting resistance due to the above, the run-out of the core is more effectively suppressed.

The drill 10 of the present embodiment has a high rigidity that can withstand a large cutting force while securing a groove depth necessary for chip discharge since the web core thickness is about 30% of the drill diameter. The resulting rice ball-shaped core runout is more effectively suppressed.

In this embodiment, the chisel angle ε is about 155.
°, it is difficult for the corner of the chisel edge 16 to be the instantaneous center of rotation, and in this respect too, the rice ball-shaped run-out is suppressed.

In the above embodiment, the inner cutting edge 2
Although 0a and 20b are formed in an arc shape, like the drill 30 shown in FIG. 3, the torso-shaped thinnings 34a and 34b (shaded lines in the drawing) are such that the inner peripheral side cutting edges 32a and 32b are substantially linear. Part) can also be applied. In this case, since the thinning area is wider than that of the above-described embodiment, the chip pocket is correspondingly larger, and the chip discharging performance is further improved. The connecting portion between the outer peripheral end of the inner peripheral cutting edge 32a, 32b and the outer peripheral cutting edge 18a, 18b is formed to have a smooth radius, so that the inner peripheral cutting edge 32a,
The end of the drill shaft 32b on the side of the drill shaft center bends around the drill shaft O with a relatively small radius of curvature after crossing the corner of the chisel edge 16. The length of the chisel edge 16 is substantially the same as that of the above embodiment, and the chisel angle ε is about 140 °.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention can be embodied in other forms.

For example, the drills 10 and 30 of the above-described embodiment are used.
Is a solid material, but a cemented carbide, ceramic, diamond ultra-high pressure sintered body, or CBN ultra-high pressure sintered body tip is fixed to the tip or cutting edge by brazing or the like. Is also good.

Although not specifically exemplified, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a bottom view of a toe-shaped thinning drill with a chisel according to an embodiment of the present invention.

FIG. 2 is a side view showing a tip of the drill of FIG. 1;

FIG. 3 is a bottom view showing another embodiment of the present invention.

FIG. 4 is a diagram illustrating some examples of conventional thinning.

[Explanation of symbols]

 10, 30: Tomoe type thinning drill with chisel 14a. 14b: Cutting edge 16: Chisel edge 18a, 18b: Outer cutting edge portion 20a, 20b, 32a, 32b: Inner cutting edge portion 22a, 22b, 34a, 34b: Tomoe type thinning O: Drill axis S: Straight line

Claims (5)

[Claims] 1. A drill having a straight chisel edge crossing a drill axis in a bottom view, and a pair of cutting edges from both corners of the chisel edge to the outer peripheral edge of the drill are provided symmetrically with respect to the drill axis. A drill having a chisel, wherein the cutting edge has a shape that is convex in the drill rotation direction when viewed from the bottom, and is gradually approached to the drill axis from the outer peripheral edge of the drill toward the drill axis. ,
A tom-type thinning drill with a chisel, characterized in that a tomical thinning is provided so that the end portion of the drill shaft side is further approached to the drill shaft center beyond the corner of the chisel edge. 2. The chisel edge according to claim 1, wherein the chisel edge has a diameter equal to or less than 10% of a drill diameter, and a drill axis side end of the cutting edge extends from a corner of the chisel edge by at least half the length of the chisel edge. Tomoe type thinning drill with chisel, characterized in that: 3. The cutting edge according to claim 1, wherein the cutting edge is formed at a position offset in a drill rotation direction by a predetermined dimension from a straight line passing through a drill axis in a bottom view and substantially parallel to the straight line. A toe-type thinning drill with a chisel, comprising: a blade portion; and an arc-shaped inner peripheral side cutting edge portion smoothly connected to an inner peripheral end portion of the outer peripheral side cutting edge portion. 4. The outer peripheral side cut formed at a position offset in a drill rotation direction by a predetermined dimension from a straight line passing through a drill axis in a bottom view as defined in claim 1 or 2, wherein the cutting edge is substantially parallel to the straight line. A toe-type thinning drill with a chisel, comprising: a blade portion; and a linear inner peripheral side cutting edge portion obliquely connected to an inner peripheral end portion of the outer peripheral side cutting edge portion. 5. The toe type thinning drill with a chisel according to claim 3, wherein the end of the cutting edge on the drill axis side projects beyond the straight line to the opposite side.