PURPOSE: To facilitate setting of a transistor by a method wherein a screw part is provided inside of an insulating bush, and a setting screw is screwed in.

CONSTITUTION: Female screw processing is performed to the setting screw inserting part of the insulating bush 5. Both sides of the outside circumference of the flange part thereof are cut off contriving to facilitate use of a spanner. By this constitution, when the bush 5 is fastened by the screw 3 without using a spring washer, the bush is locked by itself owing to moderate elasticity provided to the insulating resin material, and is not loosened by vibration or an impact. When the length of the screw is selected properly, the tip thereof is not protruded from the bush 5 and no contact with a lead 8b is generated, the number of parts is reduced and assembling time is shortened.