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Machine Guarding

Part Revolution Mechanical Press Part revolution mechanical press

A Part Revolution Clutch, as defined by OSHA, [29 CFR 1910.211(d)(6)], is a type of clutch that can be disengaged at any point before the crankshaft has completed a full revolution and the press slide has completed a full stroke.

The majority of part revolution presses are air clutch and brake. They are designed to trap air in a chamber or tube. When compressed air is put into these chambers, the clutch is engaged and the brake is disengaged. The press then makes a single stroke. To stop the press, the reverse takes place.

Operator Involvement

This type of press is not as dangerous as the full revolution clutch press. However, hazards still exist. Here, the operator must keep the operating controls depressed throughout the machine stroke. A release of either control will stop the press action.

PencilNote: Many older models of part revolution clutch presses use a mechanical-friction clutch. These types of presses are generally not as safe but can be updated by adding a properly sized air cylinder to the part revolution control.

For a printable sample form of a periodic inspection record for partial revolution power presses, please see Appendix E.

Point of Operation


  • The biggest hazard when working with either full or part revolution mechanical power presses is the point of operation. A hand or any body part in this area can result in crushed or severed limbs or even fatalities.


  • The following are OSHA and ANSI recognized methods for safeguarding the point of operation on part revolution clutch mechanical power presses:

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