Reaction Torque

Last Updated: August 28, 2020

Definition - What does Reaction Torque mean?

Reaction torque is the force that acts on an object when it is not free to rotate. In the workplace setting, reaction torque usually refers specifically to the force produced by electrically powered tightening tools. This torque force occurs when the tightening cycle is complete and can be quite abrupt. Failure to mitigate the effect of this force can cause injury or musculoskeletal damage to the tool's operator. Reaction torque is also referred to as torque reaction.

WorkplaceTesting explains Reaction Torque

Torque refers to the twisting force applied to a fastener. The resistance produced when this twisting force can not move the object is called reaction torque. Using a wrench to attempt to loosen a frozen bolt can produce reaction torque. With regard to electrical power tools used to tighten threaded fasteners, reaction torque occurs when the tool enters the final phase of the tightening process. When the parts of the fastener are joined and can no longer be turned, the force being exerted by the tool is transferred back to the tool as reaction torque.

This is important to consider on a worksite as this force may then be distributed to the hand and arm of the tool's operator and trigger a reflexive muscle reaction. Prolonged or repeated exposure to reaction torque may result in injury or musculoskeletal damage to the operator. The risks of reaction torque can be reduced by the use of specialized tools designed to detect and limit torque reactions.

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