Code 1747 applies to employers engaged in grinding or crushing emery, talc or other minerals that have no more than 5% free silica content, to a fine powder.  The term “free silica” for the purpose of this interpretation means pure silica or contains more than 5% pure silica content.

Bulk minerals are first crushed into chunks, then pulverized into a fine powder using roll mills and conveyor type equipment.  The powder is screened to size and may be washed to remove any impurities and then dried.

This classification is also assigned to the cleaning of castings to remove burrs by a tumbling method using sawdust, corncob or steel shot, but not by sandblasting.  Castings to be cleaned are placed in drums with sawdust, corncob or steel shot and tumbled until rough edges are removed.  This cleaning is assigned to this classification when performed as a service for customers, but not when cleaning is done by casting manufacturers.