Grinding machines need enough power to hold spindle speed at safe levels under every normal operating condition. They must carry safety guards that conform to ANSI B7.1-1970 (the abrasive wheel safety code) and to this section. The guard must cover the flange projections, the nut and the spindle end, stays aligned with the wheel, and is held by fastenings stronger than the guard itself; exposure of the outer flange, nut and spindle end is allowed where the work itself protects the operator, the guard side covers may be omitted where the work covers the whole side of the wheel, and portable saws may have those parts exposed. Floor stand and bench wheels used for external grinding need protection hoods strong enough to withstand a bursting wheel, with angular exposure of periphery and sides of no more than 90 degrees, or 125 degrees where the work has to touch the wheel under the spindle's horizontal plane, and in either case exposure starts no more than 65 degrees above that plane. These grinders also need work rests that are rigidly supported, readily adjustable and kept within one-eighth inch of the wheel face. Cup wheels for external grinding need a revolving cup guard or band guard per ANSI B7.1-1970. Other portable wheels for external grinding need hoods meeting (c)(5), except that safety flanges are used where the work location makes a hood impossible, and wheels 2 inches or smaller in diameter firmly mounted at the tip of a steel mandrel need neither. Portable wheels for internal grinding need safety flanges unless the wheel is 2 inches or less on a mandrel or sits wholly inside the work. Required hoods are mounted aligned and strong enough, with fastenings, to hold fragments if the wheel breaks, with a 180 degree maximum exposure; required safety flanges are used only with wheels designed for them and must be of a type that retains the pieces of a broken wheel. Before mounting, every wheel gets a close inspection and a ring test to find cracks or defects, must fit freely on the spindle without forcing, and the spindle nut is tightened only enough to hold it. Anyone using abrasive wheels needs subpart E eye protection unless an eye shield is permanently fixed to the bench or floor stand. All abrasive wheels and tools must meet the other applicable parts of ANSI B7.1-1970. On offhand grinders the work rest supports the work, is rigid and adjustable for wear, is kept no more than 1/8 inch from the wheel, is clamped securely after each adjustment, and is never adjusted while the wheel turns.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.