The angle grinder is the most dangerous handheld power tool on a construction site — not because it is inherently defective, but because workers regularly remove the guard, use the wrong wheel, and operate at speeds that exceed the wheel's rating. Angle grinder injuries are catastrophic: wheel fragments travel at 200 mph and cause amputations, punctures, and eye damage. There are no second chances with a grinder.

• Check the wheel for cracks or chips before mounting — ring test: tap the wheel gently with a wooden mallet; a clear ring = intact; a dull thud = discard the wheel
• Match the wheel's maximum RPM rating to the tool's no-load RPM — using a slower-rated wheel on a faster grinder is a wheel explosion waiting to happen
• Verify the wheel is rated for the application: cutting wheels are for cutting only, grinding wheels for grinding. A cutting wheel used for grinding flexes and can shatter
• Check that the guard is in place and functional — do not remove or modify the guard for any reason

• Use both hands on the grinder at all times — a wheel catch or kickback will pull the grinder hard and fast
• Keep bystanders at least 25 feet clear — a disintegrating wheel sends fragments in all directions
• Never use a grinder on an aluminum surface with a steel-wire wheel — aluminum-steel friction creates a fire hazard and can jam the wheel
• Eye protection: face shield over safety glasses — safety glasses alone are not enough against grinding sparks and wheel fragment risk
• Allow the wheel to reach full speed before touching the work surface — and allow it to stop completely before setting it down