Patent ID: 7837418
Filing Date: 2010-11-23
Classification: B23B,Y10T

Abstract:
1. A twist drill for the machining of aluminum alloys, said twist drill having an overall diameter, said twist drill comprising: a drill shaft configured to be inserted into a tool holder; a drill tip comprising a primary cutting edge; a body portion extending from said shaft to said tip; said body portion comprising spiral chip flutes; said body portion comprising lands disposed between adjacent chip flutes; said lands each comprising a clearance surface and a circular surface, said circular surface precedes said clearance surface in the direction of rotation of the twist drill; said spiral chip flutes together define a central drill core or web portion therebetween having a width; said drill core having a width at the drill tip that is (15±3)% the diameter of the twist drill; one of: said drill core width and the drill diameter tapers or decreases in size from said drill tip toward said shaft; said circular surface and a first plane containing said primary cutting edge and the direction of rotation of the twist drill at a point on said cutting edge together define a primary clearance angle measured in a second plane perpendicular to the first plane; said clearance surface and the first plane together define a secondary clearance angle measured in the second plane; and said secondary clearance angle being greater than said primary clearance angle: wherein at least one of: said body portion, said chip flutes, said clearance surfaces and said circular surfaces have precision-ground surfaces having an average roughness of R