Twist drill bit

Details Twist drill bit Twist drill bit

1986-08-11

1988-05-17

Weidenfeld, Gil

Cutting by use of rotating axially moving tool

Tool or tool with support

Having peripherally spaced cutting edges

408145, B23B 5102

Patent

active

047447052

ABSTRACT:
A twist drill bit includes a cylindrical body having a pair of spiral grooves formed in an outer peripheral surface of the body and extending spirally along a length thereof to a forward end of the body. Each of the grooves has a forward portion defined by a first surface which is concavely arcuate when viewed from the forward end and extends from the outer periphery of the body generally radially inwardly thereof and a second surface which is convexly arcuate when viewed from the forward end and extends from an inner end of the first surface to the outer periphery of the body. Each of the first surfaces serves as a rake surface which terminates at the forward end in a cutting edge which is concavely curved when viewed from the forward end. Each of the cutting edges is coated with a hard coating which is harder than the body. The body has a web thickness of 0.25 D to 0.5 D wherein D is a diameter of said body, and the first surface has a radius of curvature of 0.20 D to 0.30 D while the second surface has a radius of curvature of 0.25 D to 0.40 D.

REFERENCES:
patent: 61208 (1867-01-01), Kasson

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