Twist drill for tough plastics

Abstract

There is disclosed a twist drill particularly adapted for drilling plastics and composite materials having a sharp point angle, typically 85.degree. to 95.degree., and a very low lip relief angle, typically 2.degree. to 3.degree.; the relief surfaces are broad, though not unusually so, and may each subtend an angle of 40.degree. to 60.degree. about the drill longitudinal axis. A two-flute drill is shown, but the structure may be modified to provide three or more flutes. Land width, helix angle, and other attributes of the twist drill are generally similar to most common varieties of twist drills for steel, wood, or other uses in drill presses or hand drills.

Dependencies are inferred from the claim text.