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Pneumatic Impact Wrenches
Technical Information

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Basics of... Pneumatic Impact Wrenches
Impact Wrenches

Impact wrenches feature a high RPM rotary-vane air motor coupled to a hammering mechanism.
Energy from the motor is converted into a series of high intensity rotary blows used for assembly and removal of various fasteners. Impact wrenches provide fast-free speed rundown before impacting and have the ability to remove stubborn fasteners with their rapid hammering action. Impact wrenches weighing only 21�?�2 Lbs. can provide over 280 Ft/Lbs of torque

Impact Wrench Selection Criteria

Bolt or Fastener Size: The size and type of bolt or fastener used in the application, as well as the required torque, will effect the selection of the best impact wrench. Consulting an "Impact Wrench Bolt Selection Chart" will help you determine the drive size and torque output of your impact wrench.

Torque Requirement: The torque required is usually obtained by a combination of the fastener size, joint type and accessory being used. If an extension bar and/or a universal joint are used, then a higher torque impact wrench is selected to compensate for the torque lost, usually 15-20% when using these types of accessories.

Joint Type: Joints are divided into either hard joints or soft joints. Hard joints are characterized by a metal to metal make up and are also referred to as hard slam joints. Once the fastener is seated there is less than 30° of fastener rotation to reach full torque. Often, soft joints must draw the mating pieces together or compress additional materials in the joint such as a gasket. Once the fastener is seated there is at least 720° of fastener rotation.

Handle Configuration: The most popular style of impact wrench is the pistol grip. The grip style handle is most common on larger impact wrenches of 1" & 1 1/2" drives. Straight "inline" impact wrenches and impact drivers are most commonly found in the 3/8' and 1/4' hex drive sizes.

Socket Retainer: The socket retainer is the mechanism used to retain a socket or accessory. The most common types and applications follow:

  • Ring: Found in automotive applications where sockets are changed frequently
  • Pin: Used in industrial assembly applications where the user assembles the same size fastener in an assembly line setting
  • Combination ring/thru-hole: Most popular style found on heavy duty automotive and industrial impact wrenches with drive sizes 3/4' and above
  • Quick Change: Commonly found on small impact drivers that use the 1/4' hex quick change retainer for driver bit retention
  • Spline Drive: Commonly found on larger impact wrenches used for off-road vehicle service, steel erection and high torque requirement
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