| 摘要 |
PROBLEM TO BE SOLVED: To realize working treatment for a joining surface capable of forming a uniform frictional working surface by bringing a conic inclined surface of form rolling dies, in which a form rolling blade having a triangular wave shape in cross section is formed, into press-contact with a joining surface of steel and form rolling it. SOLUTION: A bolt hole 11 is perforated in steel 2. A form rolling blade 38B having a triangular wave shape in cross section is concentrically formed on the conic inclined surface 38A of form rolling dies 36L, 36R respectively. Form rolling is executed in a state that the conic inclined surface 38A of the form rolling dies 36L, 36R is brought into press-contact with a joining surface of the steel 2 around the bolt hole 11. In such a way, a frictional working surface 45 having plural concentric projecting and recessing parts peak 45A, groove 45B) is formed around the bolt hole 11. The steel 2 is which the frictional working surface 45 is formed is delivered from a work table to an external part using a steel delivering means. The worked steel is superposed and firmly joined in a superposing surface with a fastening member such as a bolt or rivet.
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