Machine Guarding
The Core Mandate (29 CFR 1910.212)
OSHA's general requirement for all machines is simple in theory: "One or more methods of machine guarding shall be provided to protect the operator and other employees in the machine area from hazards such as those created by point of operation, ingoing nip points, rotating parts, flying chips and sparks."
Types of Safeguards
1. Fixed Barrier Guards
The most reliable method. A physical barrier that requires a tool to remove. If a hazard doesn't need to be accessed during normal operation, bolt a guard over it.
2. Interlocked Guards
When an operator needs frequent access (e.g., loading parts into a CNC mill), the door must be interlocked. Opening the door must immediately stop the hazardous motion. Crucially, closing the door should not automatically restart the machine; a separate start command is required.
3. Light Curtains (Presence Sensing)
Opto-electronic devices that stop the machine if the light beam is broken. Their placement is highly regulated.
The Safety Distance Formula:
Ds = K × (Ts + Tc + Tr + Tbm)
Where Ds is the minimum safe distance, K is the OSHA hand speed constant (63 inches/second), and the T variables represent the stopping times of the machine and the reaction time of the safety system.