Impact Wrenches

Impact wrenches hammer bolts loose or tight with hundreds or thousands of foot-pounds of torque. They’re fast and powerful, but the wrong socket can shatter, and the wrong habits strip, snap or over-tighten critical bolts.

• Mechanics
• Ironworkers
• Millwrights

Use impact-rated sockets only

• Impact sockets are usually black, thicker-walled and made of tougher steel that flexes under hammering.
• Chrome hand sockets are harder and more brittle. On an impact wrench they can crack or shatter and throw pieces.
• Use impact-rated extensions, adapters and universal joints, with a retaining pin or ring so the socket can’t fly off.

Torque matters

• An impact wrench doesn’t measure torque. Running lug nuts or flange bolts “until it stops” often over-tightens them, stretching studs or warping parts.
• Run bolts down snug, then finish with a calibrated torque wrench to the spec, or use torque-limiting extensions made for the job. See Torque Wrenches.
• For structural steel, follow the specified bolting method (like turn-of-nut) and your inspector’s requirements.

Using it safely

• Keep a firm grip with both hands on large wrenches; the reaction can twist the tool.
• Keep fingers away from the socket and the work; it’s easy to pinch them between the wrench and the part.
• Set the direction and power level before you pull the trigger.
• Use the lowest power setting that does the job, especially when starting threads.
• Start nuts by hand to avoid cross-threading.
• Disconnect air or remove the battery before changing sockets.

Noise and vibration

Pneumatic impact wrenches can exceed 100 dBA. Wear hearing protection. Long daily use adds up to hand-arm vibration injury; rotate tasks and use anti-vibration gloves or lower-vibration tools when you can. See Hand-Arm Vibration.

Air tools

• Use whip checks or safety couplings on air hoses, and secure the tool to the hose.
• Use the right air pressure for the tool; more pressure isn’t more safety.
• See Air Compressors.

Quick check

• Impact-rated socket, extension and adapter
• Retaining pin or ring in place
• Safety glasses and hearing protection on
• Direction and power set
• Plan to finish critical bolts with a torque wrench

Last updated: October 2, 2026