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Impact Wrenches

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Impact Wrenches

An impact wrench (also known as an air wrench, air gun, rattle gun, torque gun) is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a rotating mass, then delivering it suddenly to the output shaft.

Compressed air is the most common power source, although electric or hydraulic power is also used, with cordless electric devices becoming increasingly popular in recent times.

Impact wrenches are widely used in many industries, such as automotive repair, heavy equipment maintenance, product assembly (often called "pulse tools" and designed for precise torque output), major construction projects, and any other instance where a high torque output is needed.

Impact wrenches are available in every standard socket wrench drive size, from small 1/4" drive tools for small assembly and disassembly, up to 3.5" and larger square drives for major construction. Impact wrenches are one of the most commonly used air tools, and are found in virtually every mechanic's shop.

In operation, a rotating mass (the hammer) is accelerated by the motor, storing energy, then suddenly connected to the output shaft (the anvil), creating a high-torque impact. The hammer mechanism is designed such that after delivering the impact, the hammer is again allowed to spin freely, and does not stay locked. With this design, the only reaction force applied to the body of the tool is the motor accelerating the hammer, and thus the operator feels very little torque, even though a very high peak torque is delivered to the socket. This is similar to a conventional hammer, where the user applies a small, constant force to swing the hammer, which generates a very large impulse when the hammer strikes an object. Energy is stored over time, allowing a very strong, but short output impulse to be generated from a relatively weak, but constant input force. The hammer design requires a certain minimum torque before the hammer is allowed to spin separately from the anvil, causing the tool to stop hammering and instead smoothly drive the fastener if only low torque is needed, rapidly installing/removing the fastener.

It is most important that the sockets that are used are
specifically designated "impact wrench sockets." Sockets and
accessories which are made for hand use only will not stand up
to impact wrench use. They are subject to premature failure,
breaking and possibly causing injury. Impact type sockets
usually are identified by a black finish on the outside, and have heavier section thickness.

Always wear safety goggles or safety glasses with side shields
complying with current national standard, and a full face shield
when needed. Use a dust mask in dusty work conditions. Wear hearing protection during extended periods of operation.

Do not wear loose clothing, jewelry or any dangling objects that may catch in rotating parts or accessories. Tie back long hair.

Never use a wire, soft pin or nail to hold the socket onto the
square spindle of the impact wrench. If the proper retaining device on the tool is broken, the tool should be repaired.

Avoid excessive impacting, particularly on small bolt sizes. Small bolts could easily be broken or the threads stripped. Over torquing can cause premature failure of fasteners or other damage, and can lead to accidents.

On applications where a low or critical level of torque isrequired, it is recommended that you impact each fastener lightly, and then perform the final tightening with a hand torque wrench.

If your owner/operators manual recommends using wood boring bits with an impact wrench, be sure to unplug the tool before changing, the bits.

Do not use an impact wrench in wet or damp environments.