Impact driver

From Wikipedia, the free encyclopedia

An impact driver is a hand tool that delivers a strong, sudden torque after being struck by a hammer. In conjunction with toughened socket sets, they are often used by mechanics to loosen larger bolts and nuts that are frozen or over-torqued in place.

Impact drivers consist of a heavy outer sleeve that surrounds an inner core that is splined to it. When the user strikes the outer sleeve, its downward force works on the spline to turn the core about 90 degrees and any socket or work bit attached to it. The tool translates the heavy rotational inertia of the sleeve to the lighter core to generate large amounts of torque.

If the tool is powered by a motor instead of by manual striking, it is called an impact wrench instead, and greatly increases the versatility of this type of tool.