| 摘要 |
PURPOSE:To extend the life of a tool longer less decreasing its chipping while to improve the accuracy of cutting especially the accuracy of cutting a groove in its width, by forming a cutting broach with a material of quality improving its wear resistance better successively toward the roughing edge part, intermediate finishing edge part and the finishing edge part, in case of the broach for use of cutting a key groove or the like. CONSTITUTION:For generating a key groove K, a broach B is inserted into a prepared hole M, and the broach B, holding its extraction holding part 7 to an extracting head, is drawn out in the direction of an arrow head 14 toward a roughing edge part 2 from a finishing edge part 4. Then the broach B passes through the prepared hole M successively in the order of a front guide part 8, roughing edge part 2, intermediate finishing edge part 3, finishing edge part 4 and a rear guide part 5 finally generating the key groove K in the prepared hole M. Here the broach B generates a depth of cut about 50-100mum by the roughing edge part 2, about 20-50mum by the intermediate finishing edge part 3 and about 0-20mum the finishing edge part 4. Accordingly, the broach enables rough finishing and intermediate finishing to be performed with no generation of chipping by the roughing edge part 2 and the intermediate finishing edge part 3 in rich toughness. While the broach enables a width W of the key groove K to be high accurately cut by the finishing edge part 4 of rich wear resistance.
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