| 摘要 |
PROBLEM TO BE SOLVED: To perform stable stop of turning of a screw, operability of an index and accurate and easy positioning by disposing a base end of an index threaded part above an upper end of an engaging groove in the state that upper surfaces of an index and a display outer shell are disposed in plane. SOLUTION: A base end 42a of a threaded part 42 of an index 4 is disposed above an upper end 34a of an engaging groove 34 in the state that an upper surface of the index 41 and an upper surface of a display outer shell 3 are disposed in plane. A nut 6 cannot move upward above the upper end 34a of the groove 34 so as not to arrive at the end 42a of the part 42, and hence an intrusion of the nut 6 into the base end 42a can be prevented. A plurality of engaging grooves 31a to be partly engaged with a sphere of a positioning member of an index base 41b are circumferentially continuously formed at an equal interval on an upper step 31 of the shell 3. When a spring is compressed as the index 4 is rotated, a sphere is intruded into the adjacent groove 31a. Thus, the index 4 can be accurately, easily positioned in response to a display position of the shell 3, thereby providing excellent attaching and detaching operability of the index 4 and stabilizing stopping of turning of a screw.
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