| 摘要 |
A rotary piercing tool for forming, in a metal plate or the wall of a metal tube, by pressure and friction-generated heat a bossed hole, said tool comprising a tapered active end portion at one end, a shank for its attachment in a chuck of a machine tool at the other end and a coaxial cavity extending from the free end of said shank to a place at a given distance from the free end of said active end portion.
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