PURPOSE: To improve the wear resistance of a screw driving part, to hold the precision for a longer time and to reduce the cost by constituting the screw driving part of a spindle, which is moved back from and forth to an anvil, with ceramics.

CONSTITUTION: A male screw part 7 provided on the side of a spindle 5 is constituted with ceramic materials, and plural male screw pieces 13 cut from a male screw member 23 which consists of the same materials as the male screw part 7 and has the same pitch as the male screw part 7 are attached to the inside circumferential face of an inner sleeve 4 to a female screw part to be engaged with the male screw part 7. In case that these male screw pieces 13 are attached to the inner sleeve 4, they are fixed with screw parts on the inside by an adhesive or the like. By this constitution, the production is made easy, and the precision is held for a longer time, and the cost is reduced.