Impact wrenches make our lives much easier. Changing a flat tire with one of these tools is certainly a piece of cake. However, despite their great utility, most impact wrenches have a huge con. They don’t let you adjust the applied torque.
So, it isn’t recommended to use an impact wrench without torque setting on rusted bolts. Excessive torque could break them easily. Even if you’re using the impact wrench out there, you’ll have to be careful when pulling the trigger to avoid causing a disaster.
Fortunately, there’s an easy way to adjust the torque applied by pneumatic impact wrenches that maybe you didn’t know. Today, we’ll tell you how to do it. Also, you’ll learn why proper impact wrench torque setting is so important.
Reasons You Need to Set Your Impact Wrenches
Unfortunately, when impact wrenches were invented, no one thought on a mechanism for controlling the applied torque. So there’s a high chance of breaking the bolts if you don’t handle your tool carefully.
Some machines require precise torque application on each of their bolts. If the torque isn’t enough, there will be vibration and friction between parts. If the torque is excessive, the bolt may break, wear the thread or puncture the retained elements. Also, if the bolt is too tight, it will be very difficult to remove in the future.
For these reasons it’s so important to adjust impact wrenches before using them. Before starting work, it’s also a good idea to take a look at the recommendations in the user manual to find out the maximum torque that can be applied to each bolt.
Impact Wrench Torque Setting Methods
Things you’ll need
- Torque setting attachment
- Air pressure regulator
Case 1: The tool has torque adjustment
Some electric impact wrenches have a control ring that lets you control the applied torque easily. To use it, you just need to turn the ring to adjust the torque to any of the preset levels on the numbered scale.
These models are comparatively better because they allow precise and effortless torque adjustment. These tools are ideal for very delicate tasks, where applying the exact torque is essential to ensure good machine calibration.
Case 2: The tool has not torque adjustment
If the impact wrench hasn’t setting option, there are three different methods to adjust the applied torque. The first is to install a special attachment between the rotating head of the wrench and the socket. This attachment limits the application of torque to a certain level, preventing serious damage to bolts and threads.
The second method is to install an air pressure regulating valve between the air hose and the impact wrench. The less air enters the wrench, the less torque it will apply. This method isn’t as precise as the first one, but it gives good results when the user knows the right amount of air pressure to obtain a certain torque.
The third method is to adjust the air pressure output with the compressor valves. This method is the least accurate of all and can affect the performance of other pneumatic tools connected to the compressor.
The first method is applicable for all impact wrench models. However, the second and third methods can only be applied in pneumatic models.
- Before using an impact wrench, carefully read the assembly instructions of the machine or structure to know how it works and the recommended torque for each bolt.
- If the assembly instructions only indicate the dry value of the torque and the bolts are lubricated, it’s recommended to apply 75%-85% of that torque.
- If you’re using a pneumatic model, be sure to properly maintain the air compressor before starting work. This includes purging the tank, cleaning the air filters, changing the oil and fixing any air leak.
- Be careful to not exceed the recommended air pressure for your pneumatic wrench. Excessive pressure could cause irreversible damage to the tool.
- If the bolt is rusty or visibly deteriorated, it isn’t recommended to use an impact wrench. In these cases it’s better to opt for a torque wrench.
As you can see, it’s possible to adjust the applied torque on any impact wrench model. You just need to follow the tips in this guide.
If you have a pressure regulating valve and an air compressor, it’s advisable to do some tests so as to determine the change in torque related to the pressure variation. Then record the obtained data in a notebook so you can consult your notes each time you need to vary the torque.
Q. 1: What is the usual torque applied on lug nuts?
A. It all depends on the size and material of the lug nut. Usually, a torque near to 100 ft.lb is required for aluminum nuts and near to 80 ft.lb for steel nuts.
Q. 2: How much torque an impact wrench should apply?
A. The impact wrench must be capable of generating the torque required by the bolt. If the torque is excessive, the bolt may break. If it’s lower, there will be friction and vibration between parts.
Q. 3: Are impact wrenches and torque wrenches the same thing?
A. No. Although both tools are useful for tightening and loosening bolts, they’re very different. Impact wrenches generate impact torque and rotation using hydraulic, pneumatic or electric power. On the other hand, torque wrenches use muscle force applied by the user.
Q. 4: Is it possible to check the torque of an impact wrench?
A. Yes. There are several ways to do it. The most popular is to tighten a bolt using an impact wrench and then measure the maximum torque required to loose it using a dial torque wrench.