In the latest instalment of its Expert Corner workshop information series, Chicago Pneumatic has issued some important advice on the use of torque limited impact wrenches and how to prevent over tightening.

The tool experts say an impact wrench with a torque limited function enables efficient torque level control, with torque limited to the forward direction to prevent overtightening. Antoine Tourneux, Global Product Marketing Manager, Vehicle Service Air Tools, at Chicago Pneumatic says, “Operators should always complete the final tightening with a calibrated torque wrench to ensure that the torque applied is accurate and complies with the vehicle manufacturers’ specifications.”

There are two types of torque limited technology, both designed to reduce power in the forward direction once a given torque is reached, mechanic modification (takes place in the wrench’s impact mechanism) and air flow modification (occurs in the impact wrench’s motor).

Chicago Pneumatic says since torque limited impact wrenches with mechanical modifications rely on a hammer and anvil making physical contact, they are inherently prone to vibration. They will also experience more friction at the contact point, which results in heat, and acts as a source of potential failure. This is where opting for tools with air flow modifications can be a big advantage. Tools with a reduced inlet air flow consume less air and have a significant benefit of reduced vibration compared to tools with mechanical modifications.

Depending on the make and manufacturer, tools with air flow modifications can also reduce vibration in the forward direction compared to tools with a non-torque limiting design. This helps to protect workers from The Hand Arm Vibration Syndrome (HAVS), a common yet debilitating musculoskeletal disorder, which is often permanent, but easily preventable, and caused by intensive and repeated vibration exposure.

No matter which technology the tool employs, both mechanical and air flow modifications ensure that once the optimal level of torque is achieved, it is not exceeded. This helps avoid the risks associated with overtightening.