An impact wrench is a wrench that uses a discontinuous drive clutch system and compressed air to achieve torque. Impact wrenches are the most commonly used tool in the world, and it is often used to tighten lug nuts on cars for tire changes.
Impact wrenches are destructive by nature with its "hammering" design. Due to the lack of proper torque control, an impact wrench can easily damage parts and the threads of a fastener. The wrench is not designed for torque control and it tends to under and over tighten the fastening application.
While the initial purchase of an impact wrench is inexpensive, the wrench is not ergonomically friendly to an operator. An impact wrench requires a high maintenance budget and typically needs service multiple times each year. For fastening applications a pulse tool will increase productivity, provide excellent ergonomics, reliability and quality.