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Subchapter 7. General Industry Safety Orders
Group 3. General Plant Equipment and Special Operations
Article 21. Use, Care, and Protection of Abrasive Wheels

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§3580. Mounting.

(a) Inspection. Immediately before mounting, all wheels shall be closely inspected and sounded by the user (ring test) to make sure they have not been damaged in transit, storage, or otherwise. The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel. Wheels should be tapped gently with a light nonmetallic implement, such as the handle of a screwdriver for light wheels, or a wooden mallet for heavier wheels. If they sound cracked (dead), they shall not be used.

NOTE: This is known as the "Ring Test." Wheels must be dry and free from sawdust when applying the ring test, otherwise the sound will be deadened. It should also be noted that organic bonded wheels do not emit the same clear metallic ring as do vitrified and silicate wheels. "Tap" wheels about 45 degrees each side of the vertical centerline and about 1 or 2 inches from the periphery as indicated by the spots in Figure A-20 and Figure A-21 of Appendix E. Then rotate the wheel 45 degrees and repeat the test. A sound and undamaged wheel will give a clear metallic tone. If cracked, there will be a dead sound and not a clear "ring."

(b) Arbor size. Grinding wheels shall fit freely on the spindle and remain free under all grinding conditions. A controlled clearance between the wheel hole and the machine spindle (or wheel sleeves or adaptors) is essential to avoid excessive pressure from mounting and spindle expansion. To accomplish this, the machine spindle shall be made to nominal (standard) size plus zero minus .002 inch, and the wheel hole shall be made suitably oversize to assure safety clearance under the conditions of operating heat and pressure.

(c) Surface condition. All contact surfaces of wheels, blotters and flanges shall be flat and free of foreign matter.

(d) Bushing. When a bushing is used in the wheel hole it shall not exceed the width of the wheel and shall not contact the flanges.

(e) Blotters. When blotters or flange facings of compressible material are required, they shall cover entire contact area of wheel flanges. Highly compressible material such as blotting paper as normally used should not exceed.025 inch in thickness. If material of lower compressibility is used, greater thickness may be necessary. Blotters need not be used with the following types of wheels:

(1) Mounted wheels.

(2) Abrasive discs (inserted nut, inserted washer, and projecting-stud type).

(3) Plate mounted wheels.

(4) Cylinders, cups, or segmental wheels that are mounted in chucks.

(5) Types 27 and 28 wheels.

(6) Certain Type 1 and Type 27A cutting-off wheels.

(7) Certain internal wheels.

(8) Type 4 tapered wheels.

(9) Diamond wheels, except certain vitrified diamond wheels.

(f) Multiple wheel mounting. When more than one wheel is mounted between a single set of flanges, wheels may be cemented together or separated by specially designed spacers. Spacers shall be equal in diameter to the mounting flanges and have equal bearing surfaces. When mounting wheels which have not been cemented together, or ones which do not utilize separating spacers, wheels specially manufactured for that purpose shall be used.

(g) Replacing safety guard. After mounting a wheel, safety guard shall be properly positioned before starting the wheel.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Repealer and new section filed 7-26-78; effective thirtieth day thereafter (Register 78, No. 30).

2. Repealer and new section filed 11-22-85; effective thirtieth day thereafter (Register 85, No. 48).

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