16. Do not overtighten the clamp nut on the grinding wheel. Excessive tightening can cause the wheel to crack during operation. 17. Make sure that the guard is in good condition and securely installed before operating grinder. 18. Do not clamp the grinder in a vise or use as a fixed grinder. 19. Never turn on the grinder with the grinding wheel or any rotating parts touching the workpiece. 20. Use only grinding wheels in compliance with ANSI standard B7.1 and rated greater than 11,000 RPM. 21. D