Machine Guarding Basics
Recognize point-of-operation hazards and work safely around guards, interlocks and emergency stops.
Table of contents
Machines do not slow down for a hand caught in them. Moving parts can crush, cut, pull in or sever a finger or arm in less time than you can react. A guard is the barrier that keeps your body out of the danger zone. Removing a guard or bypassing a safety device to save time leads to many of the worst amputations at work. Learn what each guard does, and treat any missing guard as a stop-work problem.
What You Will Be Able to Do
- Point out the dangerous parts of a machine before you use it.
- Tell a fixed guard from an interlock and a safety device.
- Do a quick guard check before you start.
- Say what an emergency stop can and cannot do.
- Respond correctly to a missing or bypassed guard.
Where the Danger Is
OSHA's general machine guarding rule is 29 CFR 1910.212. It requires guards for the point of operation, nip points, rotating parts, flying chips and sparks. Other rules cover specific machines, such as 1910.217 for mechanical power presses and 1910.219 for belts, pulleys and shafts.
| Hazard area | What it is | Examples |
|---|---|---|
| Point of operation | Where the machine cuts, shapes, bores or forms the work | Saw blade, press die, drill bit, shear |
| Power transmission | The parts that carry power to the machine | Belts, pulleys, chains, gears, couplings, shafts |
| Other moving parts | Anything that moves while the machine runs | Feed mechanisms, flywheels, robot arms, spinning stock |
And these are the motions that hurt people:
- Rotating parts can catch hair, sleeves and gloves, and wrap them in. Even a smooth, slowly turning shaft can do this.
- In-running nip points form where two parts turn toward each other, such as rollers, or a belt and pulley. They draw you in.
- Reciprocating parts move back and forth, and they can pin you against something fixed.
- Cutting, punching, shearing and bending actions do to your hand what they do to the material.
- Flying parts, such as chips, sparks, broken tools and thrown workpieces, can reach you even when you are outside the machine.
Types of Safeguards
| Safeguard | How it works | Examples |
|---|---|---|
| Fixed guard | A permanent barrier that takes a tool to remove | Mesh over a belt drive |
| Interlocked guard | Shuts the machine off or stops it from starting when the guard opens | A door on a machining center |
| Adjustable guard | Can be set to fit the stock | A band saw blade guard |
| Self-adjusting guard | Moves as the stock passes through | A lower blade guard on a circular saw |
| Presence-sensing device | Stops the motion when a light curtain or mat detects you | A light curtain on a press brake |
| Two-hand control | Needs both hands on the buttons to run | A press with two palm buttons |
| Pullback or restraint | Straps at the wrist keep your hands out of the danger zone | Some older presses |
A good guard:
- Stops any part of you from reaching the danger.
- Is firmly attached, so that it cannot easily be removed or defeated.
- Does not create a new hazard, such as a sharp edge.
- Lets you see and do the work.
- Allows oiling and cleaning without being removed, where possible.
Opening sizes matter. If you can reach through or around a guard, it is not doing its job. On a mechanical power press, for example, OSHA ties the size of the opening to the distance from the danger: an opening 1/2 to 1-1/2 inches from the point of operation can be no more than 1/4 inch wide. Opening limits vary by machine.
Before You Run a Machine
Take a minute each time you start up or return to a machine:
- Are all guards in place and secure? Are any fasteners missing?
- Do interlocks work? If the procedure calls for a check, open the guard and confirm the machine stops or will not start.
- Do you know where the emergency stop is? Can you reach it from where you stand?
- Is the area clear of scrap, tools and oil?
- Are you trained and authorized on this machine?
- Are you dressed for it? Tie back long hair. Take off rings, watches and necklaces. Roll or fasten loose sleeves.
Warning: Do not wear gloves around rotating parts such as drill presses and lathes unless the procedure says so. Gloves can get snagged and pull your hand in faster than you can let go.
Emergency Stops Are Not Lockout
An emergency stop is for stopping a machine fast when something goes wrong. It is a control. It does not remove power from the motor circuit in every design, and it does nothing about stored energy such as air pressure, hydraulic pressure, springs or gravity. Someone can also reset it.
Before you reach into a machine, clear a jam, adjust a guard or do any service or cleaning that could expose you to moving parts, the machine must be shut down, isolated and locked out under your energy control procedure. The same applies to interlocks and light curtains. They protect you during normal running, and they are not a substitute for lockout.
There is a narrow exception for minor tool changes and adjustments during normal production. It only applies when the task is routine, repetitive and part of production, and when other effective protection is in use. It is never a shortcut for a job that happens to be fast.
When a Guard Is Missing or Bypassed
Guards get removed for bad reasons: to speed up production, to see better, to clear a jam, or because they are annoying. People also tape down switches, wedge interlocks, or jump out sensors.
- Do not run the machine.
- If you see someone working without a guard or with a bypass, tell them to stop if it is safe, and report it to your supervisor immediately. Do not wait for the end of your shift.
- Tag the machine out of service if that is your procedure.
- Do not make your own repair. Guards go back on under the maintenance procedure.
If a guard gets in the way of doing the job, report it. The guard may be badly designed, and there may be a better one. You are protected from retaliation when you report safety hazards.
Common Mistakes
| Mistake | What it costs | Better habit |
|---|---|---|
| Reaching in "just for a second" | Amputation or crush injury | Stop, isolate and lock out |
| Relying on the E-stop | The machine restarts or stored energy moves | Follow the lockout procedure |
| Taping an interlock to speed up work | The next person gets hurt | Fix the reason it was bypassed |
| Using a hand to feed or clear a blade | Hand contact with the blade | Use push sticks and proper tools |
| Running a machine you are not trained on | Mistakes with no margin | Get trained and authorized first |
Check Your Understanding
1. A chain drive guard is hanging by one bolt, and the line is behind schedule. What do you do?
Stop the line if that is your authority, or tell your supervisor right away. The guard must be secured before the machine runs. Being behind schedule does not change that.
2. Paper jams in a packaging machine. A coworker hits the E-stop and starts to reach in. What is the problem?
The E-stop is not lockout. The machine could restart or stored energy could move something. It must be locked out, or the jam cleared with an approved method.
3. You open the door of a machining center and the spindle keeps turning. What does that tell you?
The interlock has failed or been bypassed. Stop the machine by normal means, tag it and report it.
4. A rotating shaft sticks out 3 inches from a coupling. It is smooth and turns slowly. Is that a hazard?
Yes. Rotating parts can grab hair, clothing or gloves even when smooth and slow. It must be guarded.
Key Takeaways
- Guards protect you from the point of operation, power transmission parts, and other moving parts.
- Know the difference between fixed guards, interlocks and sensing devices.
- Check guards, interlocks and E-stops before you run a machine.
- E-stops and interlocks are not lockout.
- Never remove or bypass a guard, and report any bypass at once.
- Tie back hair, take off jewelry, and keep sleeves and gloves away from rotating parts.