Drill bit and step feeding method

Abstract

An improved drill bit for high speed, small diameter drilling of printed circuit boards uses flute/land ratio tapering in combination with the appropriate web thickness and point, cutting or flute angles to obtain high quality, accurately positioned holes. In one embodiment, the web thickness at the tip is 15% of the drill diameter, the flute/land ratio is 2.0, the tip angle is 130.degree., the second cutting angle is 20.degree., the third cutting angle is 30.degree., the flute angle is 32.degree., the relief groove depth is 0.001", body length is 0.256" and the distance between the body end and the flute end is 0.01". Such a bit is used in connection with an air jet cooling/cleaning system and a step feed drilling method wherein the first step is between four-six times drill diameter, the second step is between two-three times the drill diameter, and the third step and subsequent steps are between 1.5-2.5 times the drill diameter.

Dependencies are inferred from the claim text.