Abstract: An object of the present invention is to provide a ball plunger wherein a main ball of the ball plunger is rotated surely and smoothly, when a mold, jig or other article is fixed, positioned, or transported. Another object is to control and keep constant the main ball projection height from a surface fixed to the ball plunger. A plurality of the sub balls are accommodated on the bottom portion of the ball roller which farther accommodates the main ball on the sub balls, thereby reducing the rolling friction between the main ball and the sub balls. Thus, the main ball rolls smoothly. The ball roller and the spring is inserted into the casing. Finally, the spring is fixed to the casing by the coupling ring such as a c-shaped ring.

Abstract: The spring plunger of the present invention comprises: a body; a stopping portion for stopping the body; a pin whose projection height from the surface of a plate is to be precisely decided; a spring connected with the pin, and spring stopper for fig the end of the spring. When the stopping portion contacts a pit surface provided on the surface of the plate, the body of the spring plunger does not proceed any more in the female screw in the plate. Thus, the pin projection height from the surface of the plate is kept constant. According to the present invention, the pin projection height from a surface of an object body such as a mold surface can be controlled easily and precisely.