BURNISHING PROCESS USING A ROTATING BALL-TOOL - EFFECT OF TOOL MATERIAL ON THE BURNISHING PROCESS

The cylindrical, machined surface of a steel bar was burnished under a rolling contact using a lathe and using a ball as a tool, i.e. a ball-tool; the ball-tool was rotated by the drive of the workpiece mounted on the lathe. To investigate the effect of the tool material on the burnishing process, five types of ball-tools, i.e. cemented carbide, silicon nitride, silicon carbide, alumina ceramic, and bearing steel were used. The burnishing force pressing the ball-tool against the workpiece ranged from 5 to 170 N and the burnishing speed was 100 m min-1. Although the burnishing (or running) distance was usually short, less than 100 m, the influence of the burnishing distance on the burnishing process was also examined by long-distance burnishing processes, continuously extending over a distance of up to 760 m. The cemented carbide ball-tool accomplished the best results among all types of ball-tools used; it produced the smoothest surface and its own surface was hardly damaged after use for long-distance burnishing. The silicon nitride ceramic ball-tool also produced a smooth surface. Neither, the silicon carbide nor the alumina ceramic ball-tool gave satisfactory results.