Peening is a technique for imparting a residual compressive stress into the surface of metals. Having the shot used to peen metal surfaces in a captive flap, allows for more control and greater access to areas that require this strengthening procedure.
Mandrels are designed to be used with cartridge rolls to help you reach hard-to-get areas in your work pieces. Screw type mandrels and forked spindles secure cartridge rolls to the tool.