Abrasive Wheel Machinery and Grinder Safety

The safety guard

Abrasive wheels may be used only on machines with safety guards, except:

• wheels used for internal work while within the work being ground;
• mounted wheels in portable operations, 2 inches and smaller in diameter; and
• types 16, 17, 18, 18R and 19 cones, plugs and threaded hole pot balls where the work offers protection.

The guard covers the spindle end, nut and flange projections, stays aligned with the wheel, and is fastened with fastenings stronger than the guard (with limited exceptions where the work itself protects the operator, and for portable saws). The guard's angular opening must not exceed the limits for the machine type.

Natural sandstone wheels and abrasive-coated metal, wood, cloth or paper discs are not covered by this section.

Reference: 29 CFR 1910.215(a)(1) · 29 CFR 1910.215(a)(2) · 29 CFR 1910.215(a)(5) · 29 CFR 1910.215(a)(2)(i) · 29 CFR 1910.215(a)(2)(ii) · 29 CFR 1910.215(b)(2)

Work rest and tongue guard

• On offhand grinders, use a work rest to support the work. Keep it adjusted closely to the wheel, with a maximum opening of 1/8 inch, so work cannot jam between the wheel and rest and break the wheel.
• Clamp the rest securely after each adjustment, and do not adjust it with the wheel in motion.
• On bench, floor stand and cylindrical grinder guards where the operator stands in front of the opening, the gap between the wheel and the adjustable tongue (top of the guard opening) must never exceed 1/4 inch. Readjust it as the wheel wears.

Reference: 29 CFR 1910.215(a)(4) · 29 CFR 1910.215(b)(9)

Ring test and speed check

Immediately before mounting, all wheels are closely inspected and sounded with the ring test:

• The wheel must be dry and free from sawdust.
• Tap it gently with a light nonmetallic tool, such as a screwdriver handle for light wheels or a wooden mallet for heavier ones.
• If it sounds cracked (dead), do not use it. (Organic bonded wheels do not ring as clearly as vitrified and silicate wheels.)

Also check the spindle speed of the machine before mounting, to be certain it does not exceed the maximum operating speed marked on the wheel.

Reference: 29 CFR 1910.215(d)(1) · 29 CFR 1910.215(d)(1)(i)

Flanges, blotters and fit

• Mount wheels between flanges at least one-third the wheel diameter. The rule lists exceptions: mounted wheels; portable wheels with threaded inserts or projecting studs; abrasive discs (inserted nut, inserted washer and projecting stud type); plate mounted wheels; cylinders, cup or segmental wheels mounted in chucks; Types 27 and 28 wheels; certain internal wheels; modified Types 6 and 11 wheels (terrazzo); and Type 1 and 27A cutting-off wheels, which have their own flange rules. Flanges are dimensionally accurate and in good balance, with no rough surfaces or sharp edges. Both flanges are the same diameter with equal bearing surface, except for Types 27 and 28 wheels and modified Types 6 and 11 (terrazzo) wheels, which use specially designed mountings. All flanges are maintained in good condition.
• Use blotters (compressible washers) between the flanges and the wheel to spread flange pressure evenly, except for wheel types the rule exempts.
• The wheel must fit freely on the spindle and stay free under all grinding conditions.
• All contact surfaces of wheels, blotters and flanges are flat and free of foreign matter. A bushing in the wheel hole must not exceed the wheel width or contact the flanges.

Reference: 29 CFR 1910.215(c)(1) · 29 CFR 1910.215(c)(6) · 29 CFR 1910.215(d)(2) · 29 CFR 1910.215(d)(3) · 29 CFR 1910.215(d)(4) · 29 CFR 1910.215(c)(9) · 29 CFR 1910.215(c)(1)(i) · 29 CFR 1910.215(c)(3) · 29 CFR 1910.215(c)(4)(i) · 29 CFR 1910.215(c)(4)(ii) · 29 CFR 1910.215(c)(4)(iii) · 29 CFR 1910.215(d)(5)