| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus capable of forming a thread suitably without causing large thickness deviation and thickness reduction on a cylindrical workpiece. SOLUTION: This apparatus for forming the thread on the cylindrical workpiece W comprises: an inner block 20 which is inserted into the workpiece W; and an outer block 50 which is provided in the state where the inner block 20 is encircled. A helical recessed groove 20c is formed on the outer periphery of the inner block 20. The outer block 50 is provided with first blocks 51 and second blocks 52 which are alternately pressed against the outer peripheral part of the workpiece W. The first blocks 51 and the second blocks 52 have a circular-arcuate projecting line 50e corresponding to the recessed groove 20c of the inner block 20 respectively and arranged alternately in the peripheral direction of the inner block 20. The inside block 20 is composed of a plurality of divided bodies 201, 202, 203 which are divided in the peripheral direction and each divided body is made can to be opened and closed in the radial direction in the inside of the workpiece W. COPYRIGHT: (C)2009,JPO&INPIT
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