1. Material of precision machining OEM parts shell coupling: alloy steel 11SMnPb30+C 2. job operation: impact forging bead blasting turning milling gadding grinding. 3.surface treatment: electroless-plating neutral salt spray test (NSS) adhesion and thickness of coating. 4. test program: mechanical properties gauge capability study geometric tolerance Form and Position Tolerance Surface Roughness. These OEM parts are suitable for both of auto producing andmaintenance services.