9.2 Mechanical Power Presses, Point of Operation & Power Transmission Guarding (1910.217, 1910.219)

9.2 Mechanical Power Presses, Point of Operation & Power Transmission Guarding (1910.217, 1910.219)

Mechanical Power Presses (29 CFR 1910.217)

Mechanical power presses cut, punch, form, or assemble metal or non-metallic materials by means of tools or dies attached to slides or rams. Because of the extreme force and rapid cycle times involved, power press point of operation guarding is subject to stringent federal oversight under 29 CFR 1910.217.

Full-Revolution vs. Part-Revolution Clutch Presses

The fundamental safety architecture of a mechanical power press depends on its clutch type:

1. Full-Revolution Clutch Presses: Once tripped, a full-revolution clutch cannot be disengaged until the crankshaft completes a full 360-degree revolution and the ram returns to its top of stroke position. Because stroke motion cannot be stopped mid-cycle, full-revolution presses pose severe amputation hazards.
2. Part-Revolution Clutch Presses: Equipped with air-clutch and friction-brake mechanisms, part-revolution presses can be disengaged and stopped at any point along the downward or upward stroke cycle.

CRITICAL EXAM COMPLIANCE RULE: Presence-sensing devices (such as optical light curtains) and two-hand controls CANNOT be used as point of operation guards on full-revolution clutch presses, because interrupting a sensor field cannot stop a stroke once initiated. They may only act as trip devices if coupled with single-stroke mechanisms and proper safety distances.

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Power Press Safeguarding Devices and Mechanisms

Point of operation protection on power presses is accomplished through guards (die enclosure guards, fixed barrier guards) or devices (presence-sensing, pullback, restraint, two-hand control, gate).

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Power Press Inspection, Maintenance & Recordkeeping (1910.217(e))

Employers must maintain a rigorous, documented maintenance program for power presses:

• Periodic Inspections: Clutches, brakes, anti-repeat mechanisms, torque monitors, and light curtains must be inspected at least weekly.
• Written Records: Employers must maintain signed inspection records showing date of inspection, inspector identity, and specific press serial numbers.
• Reporting Amputations: Under 29 CFR 1910.217(h), any point of operation injury or amputation must be reported to OSHA within 30 days if connected to PSDI operation.

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Mechanical Power-Transmission Apparatus (29 CFR 1910.219)

29 CFR 1910.219 governs the guarding of all equipment that transmits mechanical power from a prime mover (motor, engine) to driven machinery. The standard applies to all components located seven (7) feet or less above the floor or working platform.

Flywheels and Prime Movers (1910.219(b))

Flywheels located 7 feet or less from the floor must be guarded by one of the following methods:

• A complete enclosure guard constructed of sheet, perforated, or expanded metal.
• A guard railing at least 42 inches high, equipped with a midrail and a 4-inch toeboard, positioned between 15 and 20 inches from the flywheel rim.

Shafting and Projecting Shaft Ends (1910.219(c))

• Revolving Shafting: All exposed parts of horizontal, vertical, or inclined shafting 7 feet or less above floor level must be protected by a stationary casing or stationary trough guard.
• Projecting Shaft Ends: Unshielded projecting shaft ends must present a smooth edge and surface, and must not project more than one-half (1/2) the diameter of the shaft unless guarded by non-rotating caps or safety sleeves.
• Keyways, Set Screws, and Bolts: All projecting keys, set screws, and bolts in revolving parts must be countersunk, covered, or enclosed by smooth cylindrical guard sleeves. Unenclosed set screws with exposed threads are strictly prohibited.

Belts, Pulleys, and Ingoing Nip Points (1910.219(d) & (e))

• General Rule: All horizontal, vertical, or inclined belts and pulleys located 7 feet or less above the floor must be fully enclosed with fixed guards.
• Ingoing Nip Points: The exact point where a belt enters a pulley, or where a chain enters a sprocket, creates an ingoing nip point capable of drawing limbs into moving machinery. Ingoing nip points must be guarded 100% of the time regardless of belt speed.

Gears, Sprockets, and Chains (1910.219(f))

Gears — 1910.219(f)(1). Gears must be guarded by one of three permitted methods:

1. A complete enclosure; or
2. A standard guard at least 7 feet high extending 6 inches above the mesh point of the gears; or
3. A band guard covering the face of the gear, with flanges extending inward beyond the root of the teeth on the exposed side or sides. For a gear 20 inches or less in diameter the band guard must also cover the tooth face; larger gears require the band guard plus a disc barrier or a bolted-on cover over the arms and spokes.

HAND-ADJUSTMENT EXCEPTION (1910.219(f)(2)): hand-operated gears used only to adjust machine parts, which do not continue to move after hand power is removed, are not required to be guarded — although OSHA recommends guarding them.

Sprockets and chains — 1910.219(f)(3). The rule reads: "All sprocket wheels and chains shall be enclosed unless they are more than seven (7) feet above the floor or platform." Where the drive extends over other machines or working areas, protection against falling components must still be provided even above 7 feet.

Openings for oiling — 1910.219(f)(4). Where frequent oiling requires access through a guard, hinged or sliding self-closing covers must be provided.

EXAM TRAP: A widely repeated myth holds that gears, sprockets, and chains must be enclosed "no matter the height." They do not get a blanket rule. Sprockets and chains receive the same 7-foot relief as shafting, belts, pulleys, and flywheels. The gear requirement is different in kind — a choice among three methods, one of which is itself a 7-foot-high standard guard — not a height exemption. If a question offers "regardless of height," check whether it is talking about gears or about sprockets and chains before you pick it.