METHOD OF PRECISELY SHEARING PIPING MATERIAL AND APPARATUS THEREFOR

摘要

The invention has its object to provide a method of precisely shearing a piping material to provide a high-precision sheared end which has small irregularities and is free of scratches and gossan, and an apparatus therefor. The invention has a feature of performing high speed shearing with a tension applied to a piping material in an axial direction thereof, when the piping material is to be sheared by means of a mandrel. The axial tension amounts to 1.5 % or more and less than 100 % of a yield stress of the material, and a shearing speed is equal to or more about 1 m/sec. An apparatus of the invention comprises a stationary blade (3) secured to a shearing type frame (2) and provided with a hole (30), through which a piping material W is passed to a predetermined position, a floating mandrel (13) inserted into the piping material W, a movable blade (4) which has a hole (40) for permitting the piping material W to pass therethrough and a stationary mandrel (14) concentric with the hole (40), and a holder (4a) for securing thereto the movable blade (4) and adapted to be moved by a ram R. A clamp mechanism (6) is provided for clamping a tip end of the piping material W, which is fitted onto the stationary mandrel (14) to the holder (4a). Incorporated into the shearing type frame (2) rearwardly of the stationary blade (3) is a traction mechanism (7) which acts to grip the piping material W to exert a traction force thereon in an axial direction and which is capable of extending and contracting and moving in an axial direction.