JPS62188614A - Drill - Google Patents

Abstract

PURPOSE:To improve the extent of dischargeability in chips without entailing any drop in drill strength, by forming a groove width ratio of a chip discharge groove to be larger at the rear end side to the tip end side, in case of a twist drill having the twisted chip discharge groove. CONSTITUTION:This twist drill 2 is provided with a tool body 21. Two cutting edges 22 are installed in a tip of this tool body 21, while there are provided with two chip discharge grooves toward a rear end from these two cutting edges 22. Web thickness between these chip discharge grooves 23 is designed so as to become thickened gradually in proportion as going toward the rear end side from the tip end side. And, each of these chip discharge grooves 23 is formed, in its width ratio, so as to be gradually larger in proportion as going toward the rear end side from the tip end. That is to say, when the groove width ratio in both tip and rear parts of these chip discharge grooves 23 is set down to X=2alpha/360 deg., Y=2beta/360 deg., it is set so as to become X<Y in design.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a twist drill in which the groove width ratio of the chip discharge groove is larger on the rear end side than on the front end side.

"Prior Art" As a conventional twist drill, for example, a twist drill l as shown in FIGS. 5 to 7 is known.

This twist drill I is provided with two chip discharge grooves 13.13 extending from the two cutting edges 12.12 at the tip of the tool body 11 toward the rear end of the tool body.

This chip discharge groove 13 is formed with a constant groove width ratio from the tip to the rear end, and is
It is formed with a so-called core thickness taper in which the core thickness of 3.13 mm gradually increases from the tip to the rear end.

"Problem to be Solved by the Invention J" By the way, in the above twist drill 1, as shown in FIGS. 6 and 7 (A) and (B), the groove width ratio of the chip discharge groove 13 is The core thickness taper is constant from the tip to the rear end and becomes thicker from the tip to the rear end.As a result, the groove cross-sectional area at the tip and rear ends of the chip evacuation groove 13 is The problem is that the chip becomes smaller from the tip to the rear end, which reduces chip evacuation performance.This problem also occurs when the chip evacuation groove is long compared to the outside diameter of the drill. This is more noticeable in long drills.

On the other hand, it is also conceivable to make the cross-sectional area of the chip discharge i13 constant by keeping the core thickness constant. However, this is not preferable because the strength of the drill decreases.

``Object of the Invention'' An object of the present invention is to provide a drill that can improve chip evacuation without reducing strength.

"Structure of the Invention" This invention has a structure in which the groove width ratio of the chip discharge groove is larger on the rear end side than on the front end side.

be.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a diagram showing a twist drill 2 according to the present invention. This twist drill 2 is a tool body 2! have. At the tip of this tool body 21, there are two cutting edges 22.
22, and two chip discharge grooves 23, 23 are provided from these two cutting edges 22 toward the rear end. This chip discharge groove 23 is formed to have an arcuate cross section, and the core thickness between these two chip discharge grooves 23 and 23 is as follows.
The thickness gradually increases from the tip to the rear end.

The chip discharge groove 23 is formed such that the groove width ratio thereof gradually increases from the tip toward the rear end. That is, FIGS. 2 and 3 (A), (B
'), the groove width ratio at the tip and rear ends of the chip evacuation groove is set to X=2α/360°, Y=2β/360°.
Then, it is set so that X<Y. Note that the groove width may be widened either on one side of the groove or on both sides of the groove, as shown by diagonal lines in FIGS. 4(A) and 4(B').

In this way, in this twist drill 2, the groove width ratio of the chip discharge groove 23 is gradually increased from the tip toward the rear end, so that the width ratio of the chip discharge groove 23 is increased while maintaining the core thickness taper. The cross-sectional area can be kept constant or increased, so chip evacuation can be improved without reducing the strength of the drill. As a result, it is possible to perform deep hole machining in which it is difficult to discharge chips, and since the chips can be discharged well, it is possible to prevent scratches and the like from occurring on the inner wall surface of the machined hole.

In addition, in the above embodiment, the rate of increase in the groove width ratio from the tip to the rear end side is constant, but there is no need to limit it to this, and the groove width ratio does not increase from the tip to a certain position, The groove width ratio may be increased from there toward the rear end, or may be increased in steps.

Further, in the above embodiment, the chip discharge groove is formed to have an arcuate cross section, but it is not limited to this, and may be formed in any shape such as a U-shape in cross section.

"Effects of the Invention" As explained above, according to the present invention, the groove width ratio of the chip discharge groove is made larger on the rear end side than on the front end side, which reduces the strength of the drill. It is possible to improve the evacuation of chips without causing any damage.Inner wall surface 4 of the machined hole This has the added effect of preventing scratches and the like from occurring.

[Brief explanation of drawings]

1 to 4 are views showing one embodiment of the present invention, in which FIG. 1 is a side view thereof, FIG. 2 is a sectional view along its length, and FIG. Fig. 2 is a sectional view taken along line A-A in Fig. 2, Fig. 3 (B) is a sectional view taken along line β-B in Fig. 2, and Fig. 4 (A) is a case where one side of the groove is widened. 4(B) is a sectional view showing the case where both sides of the groove are widened,
5 to 7 are views showing a conventional twist drill, in which FIG. 5 is a side view thereof, FIG. 6 is a sectional view along its length, and FIG. 7(B) is a sectional view taken along the line AA in FIG. 6, and FIG. 7(B) is a sectional view taken along the line BB in FIG. 2...Twist drill, 23...Chip discharge groove.

Claims (1)

[Claims] In a twist drill with a twisted chip evacuation groove,
A twist drill characterized in that the groove width ratio of the chip discharge groove is larger on the rear end side than on the front end side.