PURPOSE: To prevent a pad from damaging by forming the contact face of the end in a rounded shape, and forming a support in a platelike state so that the end becomes oblique with respect to the surface of the pad, thereby alleviating a force to be applied to the pad.

CONSTITUTION: A contact stylus 4 is formed at the contact face with the pad of an end 41 in a rounded shape, and a support 42 is formed in a platelike state to bend vertically. Further, the central axis of the part near the end 41 becomes oblique with respect to the surface of the pad 2. Or, the shape of the end 41a is formed in a semispherical shape to further improve the wear resistance of the end 41a. Thus, pressure to be applied to the pad can be alleviated to prevent the pad from damaging.