Importance

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Abstract

A bi-metal drill bit includes a body defining a cutting end and a shank end. At least a portion of the cutting end is formed of a first metal section and at least a portion of the shank end is formed of a second metal section that is welded to the first metal section. The first metal section has a first metal having a material hardness that is higher than a second material hardness of the second metal section. One of the first and second metal sections is treated either by coating or oxide treating so as to have a recognizable different appearance than the other of the first and second metal sections. A length to diameter ratio of the first metal section has been optimized to allow electrical resistance welding, provide better strength in the rear end after the tip breaks through a workpiece, and to minimize cost.

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First Claim