California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 7 - General Industry Safety Orders
Group 3 - General Plant Equipment and Special Operations
Article 21 - Use, Care, and Protection of Abrasive Wheels
Section 3578 - Permissible Wheel Exposure for Periphery Grinding

(a) Bench and Floor Stands. The angular exposure of the grinding wheel periphery and sides for safety guards used on machines known as bench and floor stands should not exceed 90 degrees or one-fourth of the periphery. This exposure shall begin at a point not more than 65 degrees above the horizontal plane of the wheel spindle. (See Figure A-1 of Appendix A.)

Whenever the nature of the work requires contact with the wheel below the horizontal plane of the spindle, the exposure shall not exceed 125 degrees. (See Figure A-2 of Appendix A.)

(b) Cylindrical Grinders. The maximum angular exposure of the grinding wheel periphery and sides for safety guards used on cylindrical grinding machines shall not exceed 180 degrees. This exposure shall begin at a point not more than 65 degrees above the horizontal plane of the wheel spindle. (See Figure A-3 of Appendix A.)

(c) Surface Grinders and Cutting Machines. The maximum angular exposure of the grinding wheel periphery and sides for safety guards used on cutting machines and on surface grinding machines which employ the wheel periphery shall not exceed 150 degrees. This exposure shall begin at a point not less than 15 degrees below the horizontal plane of the wheel spindle. (See Figure A-4 of Appendix A.)

(d) Swing Frame and Automatic Snagging Machines. The maximum angular exposure of the grinding wheel periphery and sides for safety guards used on machines known as swing frame and automatic snagging machines shall not exceed 180 degrees, and the top half of the wheel shall be protected at all times. (See Figure A-5 of Appendix A.)

(e) Top Grinding. In operations where the work is ground on the top of the wheel, the exposure of the grinding wheel periphery shall be as small as practical, with a maximum exposure of 60 degrees. (See Figure A-6 of Appendix A.)

(f) Guard Exposure Angles. The maximum exposure angles specified above shall not be exceeded. Visors or other accessory equipment shall not be included as a part of the guard when measuring the guard opening, unless such equipment has strength equal to that of the guard.

(g) Exposure Adjustment. Guards of the types described in subsections (a) and (b) of this section where the operator stands in front of the opening, shall be constructed so that the peripheral protecting member can be adjusted to the constantly decreasing diameter of the wheel. The maximum angular exposure above the horizontal plane of the wheel spindle as specified in subsections (a) and (b) of this section shall never be exceeded, and the distance between the wheel periphery and the adjustable tongue or the end of the peripheral member at the top shall never exceed one-fourth inch. (See Figures A-7, 8, 9, 10, 11, and 12 of Appendix B.)