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What is a Nutrunner?

A pneumatic torque wrench, also known as a nutrunner, is a member of the industrial torque wrench family – a series of tools used to tighten nuts, bolts, and screws in situations where torque is crucial. Unlike standard wrenches, torque wrenches are capable of applying a defined level of torque to a bolt. By being able to gauge the tightness of a bolt, operators can ensure that they’re successfully meeting the project specifications a job or project.

Dating back to the 1930s, a nutrunner consists of a gearbox or a torque multiplier attached to a powerful air motor. At the bottom of the multiplier is an absorption platform capable of minimizing impact so that the user can successfully secure industrial bolts with little effort. These multipliers or gearboxes have multiplication ratios that allow for control of the amount of torque applied to the nut.

In this post, we’ll discuss when it’s necessary to use a nutrunner and how to ensure that your nutrunner provides the best level of accuracy.

When To Use a Nutrunner

Pneumatic torque wrenches are often used in heavy construction industries where the tightness of a bolt or a nut needs to meet certain specifications. These industries may include power generation, mining, steel, railroad, and manufacturing. When nutrunners use pneumatic power they are an especially safe option for jobs involving flammable liquids, gases, and chemicals.

What is the Difference Between a Pneumatic Torque Wrench and a Standard Impact Wrench?

A pneumatic torque wrench is often confused with a standard impact wrench because they are very similar in appearance. However, a pneumatic torque wrench is an industrial torque wrench powered by continuous gearing. On the other hand, a standard impact wrench (also known as an air wrench), builds power in a rotating mass and releases it in small increments or “hammers” against the output shaft. While nutrunners are used to apply a critical torque specification to industrial bolts, impact wrenches are commonly used in general maintenance or assembly work.

How to Ensure the Accuracy of Your Pneumatic Torque Wrench

Because pneumatic wrenches are used in heavy industry where accuracy is critical, it’s important to ensure your tool is accurate and well calibrated. A poorly calibrated or inaccurate nutrunner can lead to disastrous results. Accurate bolt tightening is crucial for safety, especially for projects involving heavy infrastructure or hazardous materials. A good pneumatic torque wrench should be +/- 5 percent accurate with 2 percent repeatability. Below are three factors that can heavily influence the accuracy of a nutrunner:

Tool Quality

Nutrunners are complex tools made-up of gearboxes with pneumatic air motors. With so many moving parts, poorly constructed tools may leave a lot of room for error. Be sure that the tool is high quality if new or in good condition if used. Check that the gearboxes have bearings on each gear and evaluate the gear grades as well.

Air Quality

Because air powers the motor and turns the gearbox, ensuring that only high quality, clean air is used to power the wrench is crucial. Wet or dirty air can not only dramatically impact the accuracy of the tool, it can cause problems or damage over long periods of time. Additionally, the amount of air used to generate the motor needs to be adequate for the tool to function as intended.


The number one way to ensure the accuracy of a pneumatic torque wrench is to make sure it is calibrated and verified on a regular basis. There are a number of service providers that have calibrated measuring equipment and can measure and certify the accuracy of your wrench. Frequent calibration and measurement is essential – only tools that have been properly serviced are capable of meeting project specifications. To guarantee your tool is functioning properly, be sure to certify it with a ISO17025 calibration certificate.

If you’re pneumatic torque wrench needs repaired or calibrated, give Maxpro a call. We are the largest RAD pneumatic torque wrench dealer and authorized repair shop in the United States. When you calibrate your wrench at Maxpro, you’ll receive an ISO/IEC 17025 accredited calibration. Contact us today to learn how to get the best performance out of your pneumatic torque wrench today.

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