Drill

Abstract

The present invention provides a drill in which three main cutting edges (14) are provided at equal angular intervals around a drill shaft center (O), and a negative angled part (20) with a radial rake angle (phi) of a negative value is provided along a circumference of the main cutting edge (14). In addition, the radial rake angle (phi) of the negative angled part (20) ranges -20 DEG <= phi < 0 DEG, and a negative angle range (L) is 0.1D or less with respect to a drill diameter (D) from a circumferential corner. A part toward the drill shaft center (O) from the part (20) is a concaved shape smoothly concaved oppositely to the drill rotation direction. Thus, cut chip discharging performance and rigidity of a tool or cutting edge strength can be improved with good balance while preventing cutting resistance and thrust resistance from increasing. This can lead to highly efficient machining by high feeding. In addition, the drill can be appropriately used for boring various kinds of materials to be cut such as cast iron requiring relatively high rigidity, normal steel, and aluminum alloy with low dischargeablity of cut chips.

Description

Technical field [0001] The invention relates to a drill bit, in particular to a drill bit capable of high-feed and high-efficiency processing. Background technique [0002] A drill bit as a rotary cutting tool for drilling is well known. In the drill bit, a plurality of spiral grooves are provided around the axis of the drill bit, and a main cutting groove is formed along each spiral groove on the portion of the spiral groove that is open at the front end of the drill bit. In addition, a thinning chisel edge that is smoothly connected to the main cutting edge is provided near the drill axis center of the drill tip. The drill described in Patent Document 1 is an example. On the outer peripheral portion of the main cutting edge, a negative corner portion with a negative radial rake angle when viewed from the tip side of the drill bit is provided at the outer corner. Within the initial predetermined range, the strength of the cutting edge near the corner of the outer edge can be in...

AI Technical Summary

Problems solved by technology

[0005] However, the drill described in the above-mentioned Patent Document 1 is a two-edged drill with two helical flutes, and the amount of feed per one rotation exceeds 0.05D (5% of D) relative to the diameter D of the drill, especially in steel cutting. In the case of high-feed machining, the amount of cut per edge becomes large, and there are cases where chipping occurs due to insufficient cutting edge strength, so the stability is not good

In addition, when the thickness of the core is increased to increase the strength of the cutting edge, the thicker chips cut at high feed curl well in the flutes without being cut off, resulting in reduced chip discharge performance, which is prone to chip damage. damage due to blockage

On the other hand, in the case of the three-edge drill described in Patent Document 2, it is not necessary to provide the negative angle described in Patent Document 1 on the outer peripheral portion of the main cutting edge in order to prevent chipping during normal drilling. However, in the case of high-feed drilling, it will induce defects in the corners of the outer edge, and due to the small curling curvature of the chips, the chip discharge performance is not good in high-speed cutting and deep hole processing.

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