Importance

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Abstract

A method and apparatus for manufacturing anchor bolts to be fixed on concrete structures, with the method comprising preliminarily heading a steel rod to form at an upper end thereof, a head having a tapered surface gradually tapering downwardly from the upper end and decreasing in diameter; forming the mail screw at the other end of rod by thread-rolling and simultaneously rolling a part adjacent to the head to form a rod-portion of a reduced diameter by gradually displacing a surface layer of the rod-portion inwardly and outwardly to give rise to an inner and outer transient swells respectively forming a stopper a tapered portion merging into the tapered surface of head; and loosely fitting and expansible sleeve on the rod-portion of reduced diameter, with the sleeve being made by die-cutting and bending a metal plate into a cylindrical shape of an outer diameter substantially equal to outer diameter of the screw. The apparatus includes a header forming the preliminary head, and a pair of rolling die assemblies each comprising a thread-rolling die to form the screw, a neck-rolling die combined therewith by a spacer and adapted to form the rod-portion of reduced diameter.

First Claim