An impact driver is a tool that delivers a strong, sudden rotational force paired with forward thrust. The force can come from a blow struck with a hammer, in a manual impact driver, or be produced mechanically in a powered one. Mechanics commonly use an impact driver to loosen larger screws, bolts and nuts that have seized through corrosion or been over-torqued, and its direction can be reversed to tighten a fastener with more torque than an ordinary screwdriver can supply.
Facts
OriginManual impact drivers came first: a heavy outer sleeve turns a splined inner core when struck with a hammer, driving the bit forward into the fastener and reducing cam-out on screws such as Phillips heads. Powered impact drivers later added a spring-driven mechanism that delivers the same rotational striking blows once torque demand exceeds what the motor alone can supply, and typically handle smaller fasteners than an impact wrench. 1 Open Questions
Introduced When (Circa)not dated in source consulted
The Wikipedia Impact driver article gives no invention date or year for either the manual or the powered form; no date found in the source consulted. Sources
1. Impact Driver (Wikipedia)
Wikimedia FoundationLede and Manual sectionQuote, Lede and Manual section
Manual impact drivers consist of a heavy outer sleeve that surrounds an inner core that is splined to it. The spline is curved so that when the user strikes the outer sleeve with a hammer, its downward force works on the spline to produce turning force on the core and any socket or work bit attached to it.
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