Self-centering drill bit with pilot tip

Details Self-centering drill bit with pilot tip Self-centering drill bit with pilot tip

1986-08-18

1990-11-06

Howell, Daniel W.

Cutting by use of rotating axially moving tool

Tool or tool with support

Having inversely angled cutting edge

408225, 408230, B23B 5102

Patent

active

049681931

ABSTRACT:
A self-centering twist drill bit 20 is formed with a "fishtail" cutting section 32 having major cutting lips 72 and 74 on a working end 26 thereof at a point angle of 190.degree.. Tip relief surfaces 76 and 78 trail cutting lips 72 and 74. A pilot tip 38 on the working end 26 extends axially from the "fishtail" cutting section 32 and is formed with a split point having leading cutting edges 40 and 42 and minor cutting lips 46 and 48. Outer surfaces 58 and 60 of pilot tip 38 are each formed with a radial relief and a back taper and joins with cutting section 32 along fillets 92 and 100 which are also radially relieved.

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Tool and Manufacturing Engineers Handbook, vol. 1, Machining, fourth edition, 1983, pp. 9-42.
Werkstattstechnik, vol. 64, No. 6, 1974, "Spezial-Wendelbohrer", p. 373.

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