| 摘要 |
This invention comprises a main body that has a proximal end and a distal end; the central axis of the proximal end extends to the distal end. The main body has recess at inside on the proximal end with punctures on the recessed periphery; each puncture has a moving part mounted on to, the moving part has its primary end and secondary end. A sleeve is in slide-fitting onto the outside of the main body, which has its central axis parallel with the central axis of the main body; inner wall of the sleeve has a plurality of push fronts, each push front contacts with the primary end of the moving part, each push front surface rises gradually from one end to the other. When the sleeve is rotating on the main body, the gradual rising push fronts are pushing the moving parts toward or away from the central axis to match with varieties of scales of work pieces.
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