GB290951A - Improvements in or relating to the manufacture of hollow metal bars - Google Patents

Abstract

290,951. Bedford, R. A. Feb. 7, 1928. Cores.-In the manufacture of hollow metal bars, such as of tool steel, by rolling a hollow billet on a core of ductile metal such as copper, as described in Specifications 115,688 and 185,639, the core, after insertion into the billet is compressed therein prior to rolling so as to avoid the tendency of the billet during rolling to produce blind or waste ends. The hollow billet is heated and a. cold core of sliding fit is inserted therein; its length being sufficient to protrude from the billet substantially equally at each end. The billet is then placed in a mechanical, hydraulic, steam or pneumatic press and the core compressed longitudinally so as to expand it radially and press it into internal contact with the billet hollow. The protruding ends are received in collars or guides to prevent them from bending during compression. Two rams may be used moving towards one another in the guides, or one ram may be used co-operating with a support for the other end of the core. In the latter case the pressure may be applied in stages and relative movement of the support and billet effected after each stage. The core may alternatively be compressed by hammering. After rolling, a length of the bar is fractured and removed from each end of the core which is then gripped in order to extract it from the bar.