| 摘要 |
PURPOSE: A bolt for automatic transmission is provided to reduce cost and weight of automatic transmission without changing the size or material of bolt. CONSTITUTION: A bolt(B) comprises a hexagonal head(1) having an expanded portion(1a) formed at the lower end of the head; and a cylindrical body(2) arranged beneath the head, and which has a male screw(2a) formed along the outer periphery of the cylindrical body. The hexagonal head has a reciprocal cone-shaped groove(1b) formed inward from the upper surface of the head. The thickness(t) measured from the apex of the reciprocal cone-shaped groove to the bottom surface of the head is 2/5 or greater with respect to the total height of the head. Thus, the bolt has a weight reduced by the volume of the groove formed at the head.
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