Manual impact drivers
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. The tool translates the heavy rotational inertia of the sleeve to the lighter core to generate large amounts of torque. At the same time, the striking blow from the hammer forces the impact driver forward into the screw reducing or eliminating cam out. This attribute is beneficial for Phillips screws which are prone to cam out. It is also excellent for use with the Robertson square socket head screws that are in common use inPowered impact drivers
Typical battery-powered impact drivers are similar to electric drills when used to drive screws or bolts, but additionally have a spring-driven mechanism that applies rotational striking blows once the torque required becomes too great for the motor alone. This shouldn't be confused with the hammer mechanism found on hammer drills, which is a longitudinal blow.Compared to an impact wrench
An electric impact driver typically delivers less torque and accepts smaller tool bits than an impact wrench. This makes the impact driver (with its often lesser torque and smaller tool bit) more suited towards driving smaller screws in for exampleReferences
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