Every hand tool, power tool and similar piece of equipment on the job must be kept safe to use, and this applies whether the employer or the worker owns it. Guarding: a power tool built to take guards must carry them whenever it is used. Exposed moving parts that workers could touch or that otherwise create a hazard (for example gears, belts, pulleys, shafts, spindles, sprockets, drums, chains, flywheels and any other moving parts) must be guarded, and the guarding must satisfy ANSI B15.1-1953 (R1958) for mechanical power-transmission apparatus. The employer must provide at least one guarding method, for example barrier guards, two-hand tripping devices or electronic safety devices, to shield the operator and others near the machine from point-of-operation, ingoing nip point, rotating part, flying chip and spark hazards. Where operating a machine exposes a worker to injury, its point of operation (where the material is actually worked) must be guarded to any applicable standard or, if none exists, designed so that no body part can be inside the danger zone during the cycle. Special hand tools for feeding and removing material may supplement that guarding but never replace it. Machines that typically need such guarding include power presses, jointers, shears and alligator shears, guillotine cutters, power saws, milling machines, portable power tools, and calenders and forming rolls. Where the outer edge of fan blades is less than 7 feet over the floor or work level, the blades need a guard whose openings are 1/2 inch or smaller. Machines meant for a fixed location must be anchored so they cannot walk or shift. Abrasive wheel guards where the operator stands facing the opening must have a peripheral member adjustable to the shrinking wheel, the angular exposure limits may never be exceeded, and the top gap from the wheel's edge to the adjustable tongue can be no more than 1/4 inch. On bench and floor stands exposure should not exceed 90 degrees (one quarter of the periphery) and must begin at a point no higher than 65 degrees above the spindle's horizontal plane, with up to 125 degrees allowed where the work must contact the wheel below the spindle's horizontal plane; on cylindrical grinders the limit is 180 degrees, again starting no higher than 65 degrees. Workers using tools who face falling, flying, abrasive or splashing objects, or harmful vapors, gases, dusts, mists or fumes, must be given the PPE that protects against that hazard, meeting and maintained under subparts D and E. Switches: hand-held platen sanders, routers, grinders with wheels of 2 inches or less, laminate trimmers, planers, shears, nibblers, jigsaws and scroll saws whose blade shanks are 1/4 inch wide or narrower may have just a positive on-off control. Drills, tappers, fastener drivers, grinders with wheels over 2 inches, disc and belt sanders, reciprocating and saber saws and similar tools need an on-off control of the momentary contact type, and a lock-on is allowed only if the finger or fingers that start the tool can release it in a single motion. Other hand-held power tools, for example chain saws, circular saws and percussion tools lacking positive accessory holding, need a constant-pressure switch that cuts power on release. The switch rules took effect July 15, 1972 and do not apply to jack hammers, rock drills, powered tampers, concrete breakers and vibrators and similar hand-operated power tools.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.