Mechanical Power Presses

Power presses punch, stamp and form metal with tremendous force. They are a leading cause of amputations in manufacturing, usually when a hand is in the die area when the ram comes down. A press can cycle in a fraction of a second, so there is no time to react. Safe press work depends on proper safeguards, maintenance, tooling, training and discipline.

• General Industry
• Manufacturing

How a mechanical press works

• A motor spins a flywheel. When the operator trips the press, a clutch connects the flywheel to the crankshaft, and the slide (ram) comes down to do the work. A brake stops the slide at the top of the stroke.
• Full-revolution presses use a clutch that, once engaged, can’t be disengaged until the slide completes the whole stroke. Part-revolution presses use a clutch and brake that can stop the slide at any point, so they allow safeguards that stop the stroke.
• The point of operation is where the die closes on the material. This is the most dangerous area, and most amputations occur there.
• Press brakes, which bend sheet metal, are also covered by OSHA’s press rules in many cases. See Press Brakes. Hydraulic presses have their own hazards. See Hydraulic Presses.

What goes wrong

• Hands in the die when the press cycles, from feeding or removing parts by hand, clearing jams or adjusting material.
• Unintended or repeat strokes from a worn clutch or brake, a failed part or a faulty control. The slide can cycle by itself, and a worker feeling safe can be caught.
• Bypassed safeguards: tied-down buttons, taped switches, a removed guard.
• Die changes and setup done without proper blocking and lockout, so a slide drops on a worker’s hands or body.
• Pinch points, flying pieces, broken dies, noise, falling parts and heavy lifting during die changes. See Noise and Lifting & Ergonomics.

What OSHA requires

OSHA’s mechanical power press standard (29 CFR 1910.217) covers guarding, controls, inspection, maintenance, training and record keeping. See Machine Guarding. Key ideas:

• The employer must provide and ensure the use of point-of-operation guards or devices on every operation that exposes workers to injury.
• The press must have a way to stop the slide that works, and a brake and clutch that are kept in good condition.
• Inspections and tests must be done regularly, and records must be kept. The standard calls for weekly checks of clutch and brake, anti-repeat feature and single-stroke mechanism on each press, with records.
• Operators and die setters must be trained and supervised.
• Employers must also follow lockout/tagout when servicing. See Lockout/Tagout.

Industry standards such as ANSI B11.1 for mechanical power presses and ANSI B11.19 for safeguarding give more detail. Some of these go beyond OSHA’s requirements.

Safeguarding

• Point-of-operation guards that keep hands out of the die area. Fixed barrier guards and interlocked guards are the most reliable, because they physically block access.
• Presence-sensing devices such as light curtains that stop the stroke if broken, used with a part-revolution press that can stop on command. They must be mounted at a safe distance.
• Two-hand controls that require both hands on the buttons to keep the press running. They must be placed far enough away that hands can’t reach the die before the stroke ends, and they must prevent one hand from operating them with a tie-down or an elbow.
• Pullbacks and restraints attached to the operator’s wrists that pull hands out as the slide descends, or limit reach.
• Hand-feeding tools such as tongs, magnets and vacuum lifters, so hands never enter the die. Hand tools are not guards, but they help.
• Automatic feeds and ejection (robots, feeders, chutes) that remove the need to put hands in the die. See Robots & Automation.

See Safeguarding Devices for how each device works and where it fits.

Safe distance for devices

• Two-hand controls and light curtains must be placed at a safety distance from the die based on how fast a hand can move and how long the press takes to stop. OSHA’s standard uses a hand speed of 63 inches per second, so the distance equals 63 inches per second times the press’s stopping time (measured at the time it stops, as the standard describes). A press that takes longer to stop needs the controls farther away.
• Stopping time can change as brakes wear. Re-measure it on a schedule, after brake repair and after any change.
• Some presses have brake monitors that detect a worn brake, and shut the press off if the stopping time gets too long.

Safe practices

• Only trained, authorized operators run presses.
• Test safeguards at the start of each shift and after die changes. Check that the light curtain stops the slide when blocked, that both hands are needed and that guards are in place.
• Use safety blocks (blocks that hold the slide up) and lockout when changing, setting or adjusting dies, or any time a worker’s body or tools enter the die area. Safety blocks must be used in addition to lockout for work inside the dies, as the standard directs.
• Report any repeat or unintended stroke immediately and stop using the press. Tag it out until a qualified person repairs it. See Tagging Out Damaged Tools.
• Keep the area clean and clear of slugs, scrap and oil. See Slips, Trips & Falls.
• Use ear protection where noise is high, and eye protection for flying chips and broken parts. See Hearing Protection.
• Keep hands and body parts out of the die area at all times, and use hand tools to remove parts and scrap.

• Never reach into the die area while the press can cycle.
• Never bypass, tape or tie down controls or sensing devices, or remove guards.
• Never let someone else operate the controls while you work in the die, unless full lockout is in place.
• Never wear loose clothing, rings or gloves that could catch.
• Never use a damaged die or a press that cycles on its own.

Maintenance and inspection

• Inspect and test the clutch, brake, anti-repeat feature and single-stroke mechanism on a regular schedule, at least weekly for presses in use, and record the results. See Clearing Jams for related safe methods.
• Check guards, interlocks, light curtains, two-hand controls, emergency stops, pneumatic and hydraulic lines, safety blocks and dies for wear and damage.
• Follow the maker’s lubrication, adjustment and repair instructions. Only trained mechanics should work on clutch and brake systems.
• Keep inspection and maintenance records, and review them when incidents occur.

Die setting and changes

• Die changes are among the most dangerous tasks. Lock out the press, release stored energy, and block the slide with safety blocks before anyone enters the die area. See Group Lockout.
• Use hoists and die carts for heavy dies. Never lift dies by hand. See Overhead Cranes & Hoists.
• Use a written procedure, and make sure die setters are trained, authorized and supervised.
• Test the press with the safeguards in place before returning it to production.
• Minor adjustments during production are not a reason to skip protection. See Minor Servicing & Alternative Energy Control.

Training and supervision

• Train operators on the press’s controls, safeguards, hazards, emergency stops, hand tools and what to do when something goes wrong. Train die setters and maintenance workers more deeply.
• Supervisors must enforce rules and never encourage shortcuts for production. Review near misses and incidents, and fix root causes. See Incident Investigation.
• OSHA has an emphasis program for amputation hazards in manufacturing, so presses draw a lot of attention. See OSHA Emphasis Programs.

Press safety checklist

• Point-of-operation guard or device in place, rated and working
• Two-hand controls and light curtains at the safe distance for the current stopping time
• Clutch, brake and anti-repeat tested at least weekly; records kept
• Safety blocks and lockout used for every die change and adjustment
• Operators and die setters trained and authorized
• No bypassed controls; repeat strokes reported and the press tagged out

Last updated: October 4, 2026