air impact wrench is a socket wrench power tool driven by compressed
air. An air impact wrench, also called a rattle gun because of the
sound it makes, is one of the most common pneumatic tools found
in the automotive workshop (and on the racetrack). Its most familiar
use is removing the nuts from a wheel so that a tire can be replaced.
The air impact wrench delivers a great deal torque, which is often
needed to twist the nuts free. A valve controls how much torque
is applied. The tool can be set to spin in either direction.
An air impact wrench should not be used for fine tightening of wheel
nuts. If the nuts are put on too tight, the bolts may fail while
the vehicle is moving, causing the wheel to shear off. An air impact
wrench should also used only be with specially hardened impact sockets,
extensions, and joints. The sockets are special 6-point types which
can stand the sudden force that the wrench generates.