PURPOSE: To make both ends machinable simultaneously, by clamping a material by a solid type collet being closed by axial movements of both first and second sleeves, while giving rotation to a work material with a spindle rotated.

CONSTITUTION: When a third sleeve 15 is moved to the right, a lever 12 turns round, pushing a pusher 13 toward the front side. The pusher 13 first moves a first sleeve 4 to the front side and the second sleeve 6 to the same side in succession whereby a collet 7A at one side of a solid type collet 7 is contracted in its diameter for the first time and thereby a material 19 is clamped, then a collet 7B of another one side is contracted in its diameter, thus the material 19 is clamped in addition. After clamping, when a spindle 1 is rotated by a gear 17, the material 19 is rotated via the first sleeve 4 and the collet 7 so that both ends of the material 19 are simultaneously machinable so favorable enough.