A contractor working on a large bridge project came to us looking for a tool for bolting steel connections.
We recommended a RAD pneumatic torque wrench. A calibrated RAD torque wrench enhances the accuracy and reliability of fastening, and helps maintain safety and performance standards.
However, the contractor opted for an impact gun (or impact wrench), citing its faster speed. While pneumatic torque wrenches generally operate at around 20 RPM, impact guns typically operate at over 1,000 RPM.
Still, was it the best tool for this job?
We conducted a head-to-head test: torque wrench vs. impact wrench. Which of these bolt tightening tools would really serve this contractor best?
Pneumatic Torque Wrench and Impact Gun Basics
First, to clear up any confusion: A pneumatic torque wrench is sometimes called a pneumatic torque gun, and an impact gun is sometimes called an impact torque wrench.
By any name, both power tools are designed for tightening bolts, and both operate differently.
Torque Wrenches
- Mechanism
Pneumatic torque wrenches use air pressure to apply torque in a controlled manner. Operators can set them to shut off automatically once the desired torque level is reached.
- Weight and Maneuverability
Often lighter (half the weight of the impact gun) and easier to maneuver, torque wrenches are great for tight spaces and extended use.
- Speed
Torque wrenches generally operate at lower speeds, which can result in longer application times.This controlled approach provides more accuracy and precision—ideal for applications requiring exact tensioning, such as structural connections or critical assemblies.
- Torque Accuracy
Quality torque wrenches can achieve very tight torque accuracy, often within +/- 5% of the set value. They ensure consistent, reliable tension on fasteners.
- Fatigue and Vibration
Torque wrenches usually don’t vibrate as much as impact guns, as the reaction arm minimizes the vibration level. As a result, users tend to become less fatigued. Smooth, consistent torque application also lowers the risk of damaging the bolt or the connected material.
Impact Guns
- Mechanism
Impact guns use a hammering action to deliver bursts of torque. This dynamic impact mechanism helps quickly loosen or tighten fasteners. Guns continue to operate until the trigger is released, meaning users must rely on their monitoring and experience to avoid over-tightening. - Weight and Maneuverability
Impact guns are designed to include the robust motor and internal mechanisms needed to generate their hammering action’s high torque output. As a result, they are bulkier and heavier than torque wrenches. - Speed
Impact guns typically operate at higher RPMs than torque wrenches, allowing for rapid fastening. This speed can lead to overshooting the desired torque. Good uses for impact guns include situations where precise torque is less critical. - Torque Accuracy
Impact guns may have a torque accuracy of +/- 20% or more, which can cause inconsistent tension on fasteners. This lack of precision can be a significant drawback in applications where specific torque values are essential. - Fatigue and Vibration
The gun’s hammering action can lead to operator fatigue, and may cause vibrations affecting tool handling and user comfort.
While both are effective as bolt tightening tools, pneumatic torque wrenches excel in precision and control. They are best suited to critical applications such as bolted structural connections, whereas impact guns are appropriate for speed and convenience in less sensitive tasks.
The Torque Wrench and Impact Gun Go Head-to-Head
How did our torque wrench vs. impact wrench match-up turn out?
We placed an A325, 7/8-inch bolt inside a Calibore load-testing device. The Calibore is a bolt tension calibrator used with several tools, including pneumatic and hydraulic torque wrenches, impact wrenches, bolt tensioners, and nut runners. Our test’s load value was 36 kips, or 36,000 pounds of load. (One kip equals 1,000 pounds.)
Then we tested a one-inch drive impact gun with over 1,000 RPM against a 3/4-inch drive RAD 10GX pneumatic torque wrench with an RPM of just 20.
The RAD tool, at half the weight of the impact gun, was much easier to maneuver. And the impact gun took more than twice as long to put the correct torque and load on the bolt. Our RAD pneumatic torque wrench achieved the correct 36 kips in just eight seconds, while the impact gun took 17 seconds.
How a Torque Wrench Improves Efficiency in Building Bridges
Based on our test, we stand by our belief that a torque wrench would have been our bridge-building contractor’s better choice.
- Speed of Operation
The RAD pneumatic torque wrench proved significantly faster than the impact gun. Reduced time to torque allows workers to complete tasks more quickly, enhancing overall productivity on large construction projects like bridges. - Automatic Shut-Off
Unlike impact guns that keep running until the operator releases the trigger, the RAD torque wrench can be set to automatically shut off once the desired torque is reached. This feature not only prevents over-torquing, which can damage components, but also minimizes the risk of operator fatigue and mistakes, leading to more consistent performance and efficiency. - Smooth Torque Application
The RAD wrench uses a gearbox and a reaction arm, which engage with the steel structure without transmitting vibration back to the operator. This smooth application of torque allows for more precise and controlled tightening of bolts, reducing the likelihood of errors and ensuring connections are secure. - Torque Repeatability
The RAD tool has a repeatability calibration of +/- two percent, ensuring the torque applied is consistent across multiple bolts. In contrast, impact guns don’t measure repeatability, which can lead to variations in bolt tension. Precision is vital on bridge construction sites, where uniform tension is critical for safety and performance. - Lightweight Design
At half the weight of an impact gun, the RAD torque wrench is easier to maneuver, allowing workers to operate it for extended periods without fatigue. This ergonomic advantage can significantly improve workflow efficiency, especially in a demanding bridge construction environment where access and mobility may be limited.
Build Better Bridges with Maxpro’s Selection of RAD Torque Wrenches
If you’re in the bridge construction field, or any other industry where you have thousands of bolts to tighten accurately and securely, Maxpro can help.
We are an accredited supplier of a wide range of RAD torque wrenches. We carry not only pneumatic but also battery-powered and electronic torque wrenches.
We’d be happy to conduct a demonstration for you, like the torque wrench vs. impact wrench test we described above, to help you choose the best and most powerful tools for your job.
And if you need your torque tools calibrated, our state-of-the-art, A2LA-accredited calibration labs can come to you. Consistent maintenance and calibration help prevent equipment failure and keep your tools ready for the most demanding tasks.
To find out how we can meet your torque wrench needs, contact us online now or call 888-315-0175.
