To prevent in advance a drum form being damaged, by absorbing a dislocation by movably attaching a pintle and by holding it in a fixed state.

A pintle 2 has a disc shape with a center protuberance part 21 protruding in a cone shape, and a disc-like bottom part 22 is stored movably up and down and right and left in a sliding compartment 13 of a clamper 1. A pressing mechanism 3 operates by confirming that the pintle 2 is inserted in a center hole of a drum, and is equipped with a cylinder 32 into which air is introduced by opening an electromagnetic valve 31 and a piston rod 33 to press the bottom part 22 from the back by moving in the cylinder 32. A tip portion 33 A fixes and holds the pintle 2 at a fixed position if it strongly makes contact with or presses the bottom part 22. If a dislocation occurs in the center hole of the drum and the pintle 2, since an inclined plane of the protuberance part 21 abuts a rim of the center hole of the drum, the pintle 2 moves in a direction A by a repelling component of force, and the dislocation of the center hole and the pintle 2 is well absorbed.