Twist drill

Cutting by use of rotating axially moving tool – Tool or tool with support – Having peripherally spaced cutting edges

Patent

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Details

76108T, B23B 5102

Patent

active

048985031

ABSTRACT:
The invention is a split-point twist drill for use in drilling holes in sandwich structures composed of a combination of organic matrix composite, titanium and steel. The drill (20) preferably has a web thickness (50) prior to splitting of between 23 and 27 percent of the drill diameter, a point angle (60) between 132 and 138 degrees, a web taper from the point to flute run out between 0.015 to 0.020 inch per inch, a chisel-edge angle (44) between 115 and 121 degrees and a splitting angle (70) between 127 and 137 degrees. Further important dimensions are a helix angle (24) of between 28 and 32 degrees and a lip relief angle (62) of between 10 and 14 degrees. Additional important splitting dimensions are a positive notch rake angle (74) of between 5 and 10 degrees, and an angle of the notch (72) to the drill axis between 32 and 38 degrees. Additionally, the margin width (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 59 and 61 percent of the drill diameter. The primary cutting edge rake angle (76) is 10 to 14 degrees positive and the width of the flat (78) at the corner is between 10 and 12 percent of the drill diameter. The preferred material is tungsten carbide.

REFERENCES:
patent: 984323 (1911-02-01), Vauclain
patent: 2936658 (1960-05-01), Riley
patent: 3387511 (1968-06-01), Ackart, Sr. et al.
patent: 4116580 (1978-09-01), Hall et al.
patent: 4222690 (1980-09-01), Hosoi
patent: 4566347 (1985-12-01), Barish

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