BI-METAL DRILL BIT

摘要

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.

主权项

1. A drill bit, comprising:
a first rod-like section having a front cutting tip portion and a rear fluted portion, and composed of a first metal; and a second rod-like section having a front fluted portion and a rear shank portion, and composed of a different second metal, wherein the front fluted portion of the second section is welded to the rear fluted portion of the first section, the first section has a first material hardness that is higher than a second material hardness of the second section, and the first section has a length to diameter ratio between approximately 0.7 and approximately 3.0.