| 摘要 |
PROBLEM TO BE SOLVED: To display a permanent set degree with high reliability by fixing a display mark to a prescribed angle position correlating with a display sign, and arranging the display sign on the free end of a shank to the rotary axis of a connecting bolt. SOLUTION: A three-dimensional one projecting display mark or a recessed display mark 9 is formed on a side wall surface 8 or a top wall surface of a head 2 and an integral collar 3. A display sign 10 is formed as an integral or divided symmetrical groove so as to be positioned in an end part of a shank 5 similarly to the display mark 9. The display mark 9 and the diaplay sign 10, and the head 2 and the display sign 10 can dissplay an actual angleθH between a reference surfaceαand a reference surface X for deciding on a relative angle position around the rotary axis q-g of a connecting bolt between a contact surface 4 of the head 2 and a plane on the free end of the shank 5.
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