A large number of revolving, rotating, reciprocating and moving parts of machinery can be said as the sources of danger and require guarding for protection against accidents. Extensive studies reveal that some characteristic groups of dangerous parts are acting as common sources of accidents in workshops. Many such major sources are as under.
1. Revolving parts, viz. pulley, flywheels, worms, worm wheel, fan, gears, gear trains, gear wheels etc.
2. Projecting fasteners of revolving parts; like bolts, screws, nuts, key heads, cotters and pins etc.
3. Intermittent feed mechanisms, viz., tool feed of planer; table feed of a shaper, ram feed of power presses and similar other applications.
4. Revolving shafts, spindles, bars, mandrels, chucks, followers and tools like drills, taps, reamers, milling cutters, and boring tool etc.
5. Rotating worms and spirals enclosed in casings, such as in conveyors and revolving cutting tool, like milling cutters, circular saw blade, saw band, circular shears and grinding wheels, etc.
6. Reciprocating tools and dies of power presses, spring hammer, drop hammers, and reciprocating presses, reciprocating knives and saw blade such bow saw, shearing and perforating machines and the cutting and trimming machine and power hack- saws etc.
7. Moving parts of various machines, like those of printing machines, paper-cutters and trimmers, etc.
8. Revolving drums and cylinders without casing, such as concrete and other mixers, tumblers and tumbling barrels, etc.
9. High speed rotating cages such as in hydro-extractors.
10. Revolving weights, such as in hydraulic accumulator or in slotting machines for counter-balance.
11. Nips between meshing racks and pinions of machine parts
12. Nips between reciprocating parts and fixed components, such as between shaper table and the fixture mounted on it or a planer table and table reversing stops, etc.
13. Nips between crank handles for machine controls and fixed parts.
14. Projecting nips between various links and mechanisms, like cranks, connecting rods, piston rods, rotating wheels and discs, etc.
15. Projecting sharp edge or nips of belt and chain drives; via belt, pulleys, chains sprockets and belt fasteners, spiked cylinders etc.
16. Nips between revolving control handles and fixed parts traverse gear handles of lathes, millers, etc.
17. Moving balance weights and dead weight, hydraulic accumulators, counter-balance weight on large slotting machines, etc.
18. Revolving drums and cylinders uncased, tumblers in the foundry, mixers, varnish mixers etc.
19. Nips between fixed and moving parts such as buckets or hoppers of conveyors against tipping bars, stops or parts of the framework.
20. Nips between revolving wheels or cylinders and pans or tables, sand mixers, crushing and incorporating mills, mortar mills, leather carrying machines, etc.
21. Cutting edges of endless band cutting machines, wood working, and log cutting metal find stone-cutting band saws, cloth-cutting band knives, etc.
22. Nips between gears and racks strips, roller drives, presses, planning machine drives, etc.