JPH05253719A - Drill - Google Patents

Abstract

PURPOSE:To provide a drill, with which runout at the time of biting can be prevented in the same manner as a conventional cross type web thinning drill while the thrust load can be reduced, and by which the mechanical strength of the rotational center part can be improved while the occurence of defects can be prevented. CONSTITUTION:A cutting edge 13 is provided at an intersection between the wall surface to the rotational direction of two chip discharging grooves on the outer peripheral part of a drill main body, and the front end flank. A thinning edge extends from the end part of the inner circumferential side of the cutting edge 13 to the vicinity of the axis of the drill, while honing parts are provided on the cutting edge 13 and on the thinning edge. The two thinning edges are arranged so that they are separated from one another in the rotational direction perpendicular to the front end side of the thinning edge as seen from the front end side, while a chisel 17 is provided to connect the respective inner circumferential side end parts of the thinning edge together. The length of the chisel 17 is determined 0.02D-0.05D (D is the diameter of the drill).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a drill in which a cutting edge is honed and a tip flank is provided with a cross type thinning.

[0002]

2. Description of the Related Art Conventionally, the drill shown in FIGS. 5 and 6 has been provided as the above drill. In the drills shown in these figures, two twist grooves 2 are formed on the outer peripheral portion of a drill body 1 made of cemented carbide, and the cross section of the tip flank 3 and the wall surface of each twist groove 2 facing the direction of rotation. The cutting edge 4 is formed, and the tip flank 3 is subjected to cross-type thinning, thereby forming the thinning blade 5 extending from the inner peripheral end of the cutting edge 4 to the vicinity of the axis of the drill. . Further, since the drill body 1 is made of cemented carbide, a minute chamfer (hereinafter referred to as honing portion) 6 is formed on the cutting blade 4 and the thinning blade 5 by honing so that chipping does not occur in them. Has been done. In such a drill, since there is substantially no chisel that causes an increase in runout and thrust load at the time of biting, it is possible to improve the biting stability and reduce the cutting power. There is an advantage that.

[0003]

However, in the above-mentioned drill, since the honing portion 6 is formed on the thinning blade 5 constituted by the cross-type thinning, the two honing portions 6 are remarkably close to each other and are rotated. A portion P having almost no thickness is formed in the central portion. For this reason,
There has been a problem that the part P is easily damaged when the drill vibrates and is easily worn.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and not only provides various advantages of a cross type thinning drill but also prevents the rotation center portion from being chipped. The purpose is to provide a drill that can.

[0005]

DISCLOSURE OF THE INVENTION In a drill of the present invention, two thinning blades formed by thinning are arranged so as to be separated from each other in a rotation direction orthogonal to them when viewed from the tip side, and an inner circumference of the thinning blade is arranged. A chisel is provided to connect the side ends, and the length of the chisel is set to 0.
02D to 0.05D (where D is the drill diameter).

[0006]

In order to prevent an increase in thrust load, etc., the length of the chisel needs to be set to a predetermined length or less. On the other hand, a certain amount of chisel length is necessary to prevent the center of rotation from being damaged. .. The minimum and maximum of such chisel length correlates with the drill diameter. That is, when the diameter of the drill is large, the thrust load is originally large and the runout is unlikely to occur, so that the allowable length of the chisel becomes long. Therefore, in the present invention, the chisel length is set as a multiple of the drill diameter. The above numerical limits were obtained as a result of repeated experiments with various drills with different diameters,
This range is suitable for drills of all diameters as it has the advantages of the conventional cross-type thinning drill as it is, and can prevent damage to the center of rotation.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 is a side view showing a drill of the embodiment. In the figure, reference numeral 10 is a drill body. The drill body 10 is made of, for example, high speed steel,
Two chip discharge grooves 11 are formed on the outer peripheral portion thereof. The tip end side of the chip discharge groove 11 is formed in a spiral shape, and the rear end side is formed in a linear shape. A chip 12 made of cemented carbide is fixed to the center of the tip of the drill body 10 so as to cross the two chip discharge grooves 11.

A cutting edge 13 is formed at the intersection of the wall surface of the tip 12 facing the rotation direction and the tip flank. Also,
On the heel side of the tip flank of the tip 12 and the drill body 10, a thinning portion 14 is formed by scraping off toward the side opposite to the rotation direction so as to form an X shape in bottom view. Further, in the step formed on the tip flank by the thinning portion 14, the thinning blade 1 extending from the inner peripheral side end portion of the cutting blade 13 to the vicinity of the rotation center of the drill 1
5 is formed.

Further, a honing portion 16 is formed on the cutting blade 13 and the thinning blade 15. Honing section 1
As shown in FIG. 3, 6 is a flat surface that is inclined with a plane parallel to the axis of the drill at a predetermined inclination angle θ, the inclination angle θ is 10 to 45 °, and the width H is 0.03 to 0. It is set to 0.3 mm. The height M changes depending on the inclination angle θ and the width H. Then, as shown in FIG. 4, the thinning blades 15 are arranged apart from each other in the rotational direction orthogonal to them as seen from the tip side, and the chisel 17 is provided at the boundary between the two tip flanks of the tip 12. The thinning blade 15 is formed so as to connect the inner peripheral side ends thereof.

Here, the length Y of the chisel 17 is 0.02D to 0.05D, where D is the diameter of the drill. The lower limit of 0.02D is set in order to secure the necessary wall thickness at the center of rotation. However, the strength of the center of rotation depends on the width Z of the chisel 17 viewed from the direction along the cutting edge 13, rather than the chisel length Y. However,
The chisel angle α is generally set to 15 to 35 °, and within this range, the required strength can be secured with a chisel length of 0.02D.

If the size of the chisel angle α is not taken into consideration, the spacing between the thinning blades 15 is set to 0.
It is necessary to set it to 01D to 0.02D. Lower limit is 0.0
The reason why 1D is used is to ensure the width Z of the chisel 17 that is necessary and sufficient.

In the drill having the above structure, the chisel 17 is used.
Since the length Y is set to 0.05 D or less, it is possible to prevent the runout at the time of biting and reduce the thrust load as in the case of the conventional cross type thinning drill. In addition, the length of the chisel 17 is 0.02D.
As described above, the mechanical strength of the center of rotation can be increased and the occurrence of defects and the like can be prevented. Although the honing portion 16 is formed as a flat surface in the above embodiment, it may be formed as a curved surface. Further, the shape of the cutting blade and the thinning blade is not limited to the linear shape as described above, but may be various shapes such as a curved line.

[0013]

As described above, in the drill of the present invention, the two thinning blades formed by thinning are arranged apart from each other in the rotational direction orthogonal to them when viewed from the tip side, and A chisel is provided to connect the inner peripheral side ends, and the length of this chisel is set to 0.02D to 0.05D. Therefore, like the conventional cross-type thinning drill, core runout when biting is prevented. In addition to being able to reduce the thrust load, it is possible to increase the mechanical strength of the center of rotation and prevent the occurrence of defects and the like.

[Brief description of drawings]

FIG. 1 is a side view showing a drill according to an embodiment of the present invention.

FIG. 2 is a bottom view of the drill shown in FIG.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an enlarged bottom view of FIG. 1 showing the details of the center of rotation of the drill.

FIG. 5 is a bottom view of a conventional drill.

FIG. 6 is an enlarged bottom view of FIG. 5 showing the details of the center of rotation of the drill.

[Explanation of symbols]

 10 Drill Main Body 11 Chip Discharge Groove 13 Cutting Blade 14 Thinning Blade 15 Honing Part 17 Chisel

Claims (2)

[Claims] 1. A chip body is provided with two chips discharging grooves on an outer peripheral portion of a drill body which is rotated about an axis, and a cutting blade is provided at a crossing portion between a wall surface of each chip discharging groove facing the rotation direction and a tip flank. Is provided with a thinning blade extending from the inner peripheral side end of the cutting blade to the vicinity of the axis of the drill by thinning at least a portion of the tip flank that constitutes the core thickness of the drill body. In a drill provided with a honing portion for the cutting blade and the thinning blade, the two thinning blades are arranged apart from each other in a rotation direction orthogonal to them when viewed from the tip side, and the inner peripheral side end portion of the thinning blade is arranged. A drill characterized in that a chisel is provided so as to connect them, and the length of the chisel is set to 0.02D to 0.05D (where D is a drill diameter). 2. The spacing between the thinning blades is set to 0.
01D-0.02D is set, The 1st characterized by the above-mentioned.
Drill as described in the section.