The abrasive wheel grinder is one of the most commonly used pieces of machinery in maintenance shops and manufacturing facilities. While they are great for removing metal from flat or cylindrical surfaces, they can be very dangerous if not properly used or maintained. When working with this tool, take the following precautions to keep employees safe.
Guarding for Abrasive Wheel Grinders
Improper guarding of abrasive wheel grinders is one of the most frequently cited OSHA standards each year. According to OSHA, an abrasive wheel grinder should be guarded as follows:
- Side guards cover the spindle, nut, flange and at least 75% of the wheel diameter
- The work rest is present and adjusted to within one-eighth inch of the wheel
- The adjustable tongue guard is present and adjusted to within one-quarter inch of the wheel
Grinding Wheels
Grinding wheels should match the motor speed. The RPM rating of the abrasive wheel should be equal to or exceed the RPM rating of the grinder motor. Using an abrasive wheel designed for low RPM motors on a high RPM grinder may cause the wheel to break apart, increasing the risk of injury.
Testing Wheel Grinders
OSHA requires that each wheel be tested before its initial use. Abrasive wheels should also be inspected to make sure they have not been damaged while being moved or stored. This can be quickly accomplished through visual inspection and the "ring test."
To perform the "ring test," gently tap a dry clean wheel with a light, nonmetallic tool (e.g., screwdriver handle or a wooden mallet). If the wheel is in good working condition, the tap should produce a clear "ping" noise. If it makes a thud sound, the wheel is damaged and should not be used.
Personal Protective Equipment for Abrasive Wheel Grinders
Abrasive wheel grinding creates several hazards that can be controlled through the use of personal protective equipment (PPE). Recommended PPE for grinding operations includes the following:
- Safety glasses with side shields to prevent chips from reaching the eyes
- Tight-fitting gloves to protect the hands if sharp parts are being handled
- Hearing protection to prevent hearing damage from the noise created by grinding
- Filtering face masks to prevent breathing in dust
Combustible Metal Precautions
Special precautions should be taken when grinding combustible metals. According to NFPA© 484: Standard for Combustible Metals, Metal Powders and Metal Dusts, the following metals are combustible and require additional safeguards: aluminum, lithium, magnesium, tantalum, titanium and zirconium. These safeguards include:
- Minimize accumulation of combustible metal chips, shavings, powders, flakes or dusts by frequently cleaning the grinding area
- Use a hand brushing technique for cleanup (e.g., use a broom with natural fiber bristles and a nonsparking, conductive dustpan)
- Ensure that all ignition sources (e.g., welding, cigarette smoking, grinding of ferrous metals) are controlled in the areas of combustible metal grinding
- Provide a listed Class D extinguisher, or other extinguishing agent that's effective on combustible metal fires, within 75 feet of the grinder; be aware that a given agent may not necessarily control all combustible metal fires, so make sure the extinguisher provided is designed for the type of metal in use
- Avoid grinding of multiple types of metals, especially ferrous metals with combustible metals
Additional Safeguards for Abrasive Wheel Grinders
There are several other steps you can take to reduce the risk of injury:
- Permanently mount abrasive wheel grinders to a bench or pedestal using bolts of adequate strength
- Keep work area free of combustible material that could be ignited by sparks
- Keep work area well-lit so operators can easily see the workpiece and wheel at all times
- Provide a dust collection system on all grinders that produce large amounts of dust
- Ensure each grinder has its own on and off control switch
- Allow the grinder to reach full speed before use
- Turn off the grinder when not in use, as accidental contact could occur with a grinder in motion; make sure the grinder comes to a complete stop before leaving the work area