PURPOSE: To lower remarkably the Z direction of an annular body mounted on a table of a wire electric discharging machine by allowing a ball to come in and out in a through hole by a recessed part and inclined edge of the annular body while pivoting the annular body on a plane by a horizontal cylinder.

CONSTITUTION: A bolt 32 inserted through a slot 31 of a base body 11 is screwed into a table 1 of a wire electric discharging machine to mount the base body 11 on the table 1. Then, a pull stud held by a coupling 13 of a workpiece (a) supporting vice A is inserted in a hole 12 from above. Then, when an annular body 18 is pivoted clockwise by the action of a horizontal cylinder 22, a ball is got out of a recessed part 19 while the ball 17 is left under the got-out state by an inclined edge 20, so that the ball 17 engages an annular groove of the pull stud.