Patent ID: 6652203
Filing Date: 2003-11-25
Classification: B23B,Y10T

Abstract:
A drill bit comprising:an elongated body having a tip at one end and an engagement shank at the opposite end, a first portion of said body adjacent said tip having a first diameter and a second portion between said first portion and said engagement shank having a second diameter greater than said first diameter; said elongated body defining at least one flute in at least said second portion, said flute formed at a helix angle relative to the longitudinal axis of said elongated body, the helix angle decreasing from said tip to said engagement shank, wherein the helix angle starts at about 38Â° adjacent said tip and the helix angle at said engagement shank is about 15Â°, wherein the helix angle decreases from about 38Â° adjacent said tip to about 35Â° at a first distance from said tip, wherein the helix angle decreases from about 35Â° at said first distance to about 17Â° at a second distance from said tip, wherein the helix angle decreases from about 17Â° at said second distance to about 15Â° at a third distance from said tip, wherein said third distance is at least 3.5 inches, wherein the helix angle decreases substantially linearly over said third distance, wherein the helix angle decreases substantially linearly over said first distance at a first slope, the helix angle decreases substantially linearly over said second distance at a second slope that is greater than said first slope, and the helix angle decreases substantially linearly over said third distance at a third slope that is less than said second slope.