PISTON AS 4651024 - Caterpillar

When pistons are cleaned, the ring grooves must be checked for burrs and carbon. Burrs can be removed with a small file and smaller beads can be used to clean the remainder of the carbon out of the groove.
Recommendations for a glass bead size of 50-100 microns (.0020-.0039") are given in some "Guidelines For Reusable Parts." The larger Size "10" bead, 88-149 microns (.0035-.0059"), will give better results. Size "9" beads, 125-177 microns (.0049-.0070") through Size "11", 75-125 microns (.0029-.0049") are also acceptable for this application.
A bead larger than 230 microns (.0091") must never be used for engine pistons and valves, and turbochargers.
The chart which follows gives the acceptable glass bead sizes used to clean different parts, part numbers of the glass beads and suppliers.