| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of come out phenomenon without reducing the strength of a cross head part. SOLUTION: In a bit for rotary tool which is provided with cross head parts 2, 3 in which four blade parts 5 fitted in a cross groove formed in a screw head are formed symmetrically and in which an inclined face 5A inclined on a shaft core side when approaching a tip side of the head parts 2, 3 is formed in an outer peripheral fringe part of each blade part 5, a plurality of grooves 6 over the direction of width of the inclined face 5A are arranged in a row along the direction of inclination of the inclined face 5A on the inclined face 5A of the blade part 5.
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