Split-point twist drill

Details Split-point twist drill Split-point twist drill

1984-05-11

1985-12-03

Bilinsky, Z. R.

Cutting by use of rotating axially moving tool

Tool or tool with support

Having peripherally spaced cutting edges

B23B 5102

Patent

active

045563470

ABSTRACT:
The invention is a heavy-duty, split-point twist drill for use in drilling holes in high-strength materials having poor heat dissipation properties. The drill (20) preferably has a web thickness (50) prior to splitting of between 36 and 40 percent of the drill diameter, a point angle (60) between 132.degree. and 138.degree., a web taper from the point to flute run out between 0.032 to 0.038 inches per inch, a chisel-edge angle (44) between 115.degree. and 121.degree. and a splitting angle (70) between 128.degree. and 137.degree.. Further important dimensions are a helix angle (24) of between 33.degree. and 37.degree. and a lip relief angle (62) of between 10.degree. and 14.degree.. Additional important splitting dimensions are a positive notch rake angle (74) of between 5.degree. and 10.degree., and an angle of the notch (72) to the drill axis between 32.degree. and 38.degree.. Additionally, the margin (34) should be held between 9 and 11 percent of the drill diameter, the body clearance diameter (36) held between 94 and 96 percent of the drill diameter, and the land width (30) between 62 and 64 percent of the drill diameter.

REFERENCES:
patent: 2936658 (1960-05-01), Riley
patent: 3387511 (1968-06-01), Ackart, Sr. et al.

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