a two - piece , mechanically connected mandrel assembly in which a locking wedge assembly serves to secure a tapered socket connection . the wedge assembly includes two long wedge segments , two short wedge segments , a bolt connecting the short wedge segments and a locking device to fix the bolt after proper torquing to secure the assembly . the two - piece , mechanically connected mandrel assembly is useful in the rolling or drawing of steel tubing or other metal constructs , and the four - piece locking wedge assembly both provides a secure connection and permits ready replacement of a worn work bar with a new work bar .