| 摘要 |
A metal rod (20) having a conical or pyramidal cut extremity (20a) is used to make a mandrel for blind rivets. The rod is held in place between a pair of die segments (11) such that its end (26) of a preset length including the extremity is swageable and protrudes from an upper surface (14) of the segments. Subsequently, the swageable end (26) is axially compressed to form a mandrel head (27) by a punch (12) which has a lower face (17) in parallel with the upper surface (14) of the segments and a conical or pyramidal recess (18) fittable on the extremity. Thus, a free intermediate portion of the swageable end (26) compressed by the punch (12) swells radially to form the head (27) having a flat flange (31) from which the extremity protrudes as a lug (32) upwardly and centrally. The mandrel, which has the head formed uniform without any eccentricity about the axis of a mandrel body, can now be produced inexpensively using the nail manufacturing apparatus, as in the prior art method.
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