Bolt and Manufacturing Method of Bolt

摘要

The present invention provides a surface hardening portion 11 that has increased surface hardness and that is applied with a compressive residual stress, at least on the surface of a male screw 10 of a bolt 1. The present invention includes the steps of cutting to form the male screw 10 of the bolt 1, and processing to provide at least on the surface of the male screw 10 of the bolt 1 the surface hardening portion 11 that has increased hardness and that is applied with a compressive residual stress. As a result, the present invention can improve the fatigue resistance of the male screw 10 and the bolt is effective as a bolt to be used in a portion where the male screw 10 is subject to a repetitive stress.