| 摘要 |
PROBLEM TO BE SOLVED: To provide a boring tool easily manufacturable without requiring a grinding wheel and a facility of a special shape, and used for removal and removal work of a spot welding part, by improving strength of a tip cutting edge, without requiring the so-called candle grinding of setting a tip angle in two stages. SOLUTION: This boring tool has four blades of a pair of first tip cutting edges 11 of forming a first tip angleβ1 at 80°to 110°and a pair of second tip cutting edges 12 of forming a second tip angleβ2 at 170°to 190°in the same diameter d1 as an outer diameter of the first tip cutting edges 11. The tip 14 of the pair of second tip cutting edges 12 is retreated by the length (s) in the shaft direction from the tip 13 of the pair of first tip cutting edges 11. COPYRIGHT: (C)2006,JPO&NCIPI
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