How to choose an Air Impact Wrench?

Most manufacturers use 2 different time intervals, to measure tools’ torque:

Working torque: the value you need to look at considering your everyday torque needs.

A good working torque is measured within a 4 seconds time interval, because we believe this is the right amount of time to get the job done in real conditions.

Maximum torque: the best torque the tool can reach in occasional usage (removing a rusted nut for example).

As a guidance, we measure maximum torque within a 10 seconds time interval. We consider that if you can’t reach the torque you need before 10 seconds, you would need to look at a higher dimensioned tool.

For example, below is a Graph Torque/Time of Hymair 1/2'' Composite Twin Hammer Air Impact Wrench.The Working Torque should be 675Nm, and Maximum Torque should be 844Nm.

Some manufacturers will use other terms, such as “break away torque” and others. These values refer to the maximum torque measured with the tool, on a longer time interval. In other words, the tool can reach this torque, but you would need a significant time to get the job done. Not to mention that using a tool at maximum torque frequently shortens its lifespan.