The Definition of Machine Guarding

Definition of Machine Guarding

Machine guarding is the use of physical guards, safety devices and safe work practices to prevent workers from contacting the dangerous moving parts of machinery. Guards stop hands, fingers, arms, hair and clothing from reaching points where they could be cut, crushed, caught or amputated, and they also protect against flying chips, sparks and broken parts.

Machines with exposed moving parts cause thousands of serious injuries every year, including many amputations. Common danger areas include the point of operation, where the machine cuts, shapes or presses material; power transmission parts such as belts, pulleys, gears, chains and shafts; and other moving parts such as rotating spindles, feed mechanisms and reciprocating arms.

In the United States, OSHA's general machine guarding requirements are in 29 CFR 1910.212, with additional rules for specific equipment such as mechanical power presses, saws and grinders. Machine guarding is consistently among OSHA's most frequently cited standards.

Types of Machine Guards and Devices

Guards

• Fixed guards: permanent barriers that cannot be removed without tools. They are the simplest and most reliable option where access is not needed during normal operation.
• Interlocked guards: guards that shut off or disengage the machine when opened, using safety interlocks.
• Adjustable guards: barriers that can be set to fit different sizes of material.
• Self-adjusting guards: guards that open only as far as the material entering the machine, such as the blade guard on a table saw.

Safety devices

• Presence-sensing devices: light curtains, safety mats and laser scanners that stop the machine when a person enters the danger zone.
• Two-hand controls: require both hands on the controls to cycle the machine, keeping hands away from the point of operation.
• Pullback and restraint devices: straps that pull or hold an operator's hands away from the hazard.
• Emergency stops: buttons or cables that quickly stop the machine. See kill switch (emergency stop).

Good Machine Guarding Practices

• Guards should prevent contact, be secure, not create new hazards and not interfere with work more than necessary.
• Use the hierarchy of controls: design out the hazard or use engineering controls before relying on procedures or PPE.
• Never remove or bypass a guard during production. See bypassing safety devices.
• Use lockout/tagout when guards must be removed for maintenance, cleaning or clearing jams.
• Inspect guards and safety devices regularly and include them in pre-start checks.
• Train operators on how guards work, why they matter and how to report missing or damaged guards.
• Review guarding whenever a machine is moved, modified or used for a new task.

Guarding is one way to control mechanical hazards. A job hazard analysis helps identify every point on a machine where a worker could be injured.

Example of Machine Guarding

A packaging plant had a conveyor with an exposed chain-and-sprocket drive at knee height. Operators often reached near the drive to clear jammed cartons. During a safety walk, a supervisor saw an operator's glove pulled toward the sprocket before he snatched his hand back.

The plant installed a fixed mesh guard around the drive and added an interlocked access door at the jam point that stopped the conveyor when opened. Clearing jams was added to the lockout procedure, and operators were trained on the new setup. The near miss was shared across all shifts at the next toolbox talk.

Frequently Asked Questions: Machine Guarding

What is the point of operation?

It is the area on a machine where work is actually performed on the material, such as cutting, shearing, bending or punching. It is often the most dangerous part of a machine and must be guarded.

Can a worker remove a guard to clear a jam?

Only if the machine is properly shut down and locked out, or if the employer has an approved alternative method that provides effective protection. Reaching into a running machine is never safe.

What is the most common machine guarding violation?

Common violations include missing guards on the point of operation, unguarded belts, pulleys and shafts, and guards that have been removed or bypassed.