A pneumatic torque wrench is one of the best controlled bolting tools that you can use with minimal effort.
This wrench uses an air motor to deliver the torque. To control the torque, you can increase or decrease the air pressure.
Many people mistake the pneumatic wrench for the impact wrench because they look the same. However, when you get to use them, you certainly feel the difference.
The pneumatic torque wrench runs on continuous gearing or a planetary torque multiplier box. There is less vibration because it absorbs most of the impact. You can work longer and harder with it without feeling the need to give your arms a rest.
On the other hand, the air impact wrench delivers torque by impact. It has heavier vibrations, which can affect your arms.
A pneumatic torque wrench has the capability to deliver a lot of torque. Therefore, you can use it for heavier bolting jobs such as tightening truck and tractor wheel lugs. Many can deliver torque from 118 Nm to 47600Nm/88 ft-lb to 35108 ft-lb.
This torque wrench type is a combination of the precision of a manual torque wrench and the speed of an electric wrench.
This type of wrench requires a 20 to 25 CFM (cubic feet per meter) flow rate.
A) Different types of pneumatic torque wrench
Since the invention of the Pneumatic Torque wrench in Germany in the early 1980s, it has been improved a lot.
Today, there are two main types of these torque wrenches, which we will look at below:
Stall torque nutrunner
This powerful, precision bolting tool requires the operator to set up the right air pressure. Check the manufacturer’s torque chart to set up the right air pressure. Of course, the final torque is determined by the torque rating for the fastener that you are tightening.
You can use this lightweight tool for different types of tightening jobs. The torque range for a stall torque nutrunner is high, which is okay for heavy-duty jobs. To increase the torque, increase the air pressure.
As its name suggests, this tool delivers what is called “stall torque.” You get this type of torque from a device whose output rotating speed equals zero.
The most important thing to know when using this torque wrench type is to know that when you increase the air pressure, the torque increases. Use the user manual and torque chart for the tool that you are using.
Shut off nutrunner
This is the second type of pneumatic torque wrench. It shuts down when the set torque is reached. This makes it a very accurate tool to use for repeat jobs.
The user knows that the final torque is attained when it switches off. If you do not have experience using torque wrenches, this one would be the best for you.
There is not much need to check the torque setting of the device when using it for various, but similar tightening jobs.
You can also use the wrench on the constant air pressure with some of them using 90PSI. However, check the allowed torque so that you can set your wrench correctly.
If you need to tighten fasteners on plastic components, composites and metals and apply precise torque, the shut off night runner is the best bet for you.
Even with no experience, this tool is easy to use even on the most delicate of jobs. It never gets the torque wrong.
Another benefit of using this kind of tool is that it saves on air consumption because none is wasted.
Overall, these are the two types of pneumatic torque wrenches in the market. Before you can buy one, you should know the type of work you will be using it for.
Generally, shut off nutrunners are most appropriate for repetitive jobs like fastening the bolts of 18-wheelers.
You can do a faster job moving from wheel to wheel without the need to check whether the torque value you set is still holding.
B) How to use a pneumatic torque wrench
Buying any tool is good, but knowing how to use it correctly is even better. That way, you can get the full use out of it.
Fortunately, using pneumatic torque wrenches is so easy. First, these are precision tools and since they are powered by air, once you set the right PSI/CFM, it is hard to get the torque wrong.
The operation of this tool is so simple. First, there is a stop/start switch/trigger and a switch that you flick to the left or right, depending on the direction you want to tighten your fasteners.
Step-by-step guide for how to use a pneumatic torque wrench
This tool uses air for speedy application of torque. It is also very accurate, but this depends on a few things, like how you set it up.
Step 1 – Place the pneumatic wrench handle down, facing upwards on a table or other flat surface. Place the reaction arm on the precision drive system. Secure it with a locking strap. You will probably need to wear a pair of gloves for this, and even for using the wrench when you are done setting it up.
Step 2 – Place the nut on the square drive and use a locking pin to secure it in place. You can now turn the wrench over (in an upright position still) so that the handle faces upwards.
Step 3 – Connect the air supply to the wrench, through the provided high pressure coupling attached to the handle. Connect the air supply pipe to the air compressor gauge.
Step 4 – Check the torque conversion chart that came with your pneumatic torque wrench and select the right torque.
Step 5 – You have to unlock the valve for adjusting the pressure, on the air compressor gauge. However, before that, open the air shut off valve.
Step 6 – Press and hold the trigger of the pneumatic gun. Do not release it. With the other hand, open the valve for adjusting the pressure until you reach the specified pressure level. Keep your eyes on the gauge.
Step 7 – This is the step where you select the gears. You can choose the load gear/high speed gear. Also, choose your torque and the direction that you want the drive to rotate.
Step 8 – Position the reaction arm on the nut that you want to tighten and press the trigger to tighten until the set torque value is attained. It will shut off automatically when the final torque is attained.
Using this type of wrench is so simple that you can use one arm only if you are tightening fasteners that face upward.
C) How much torque does a pneumatic impact have?
Because of their high torque range, the pneumatic torque wrenches are used for heavy-duty fasteners, such as the wheel lugs used on trucks.
A pneumatic torque wrench can deliver up to 35,255 ft-lb of torque. However, this depends on the brand name and the size of the wrench.
However, this torque wrench is different from a pneumatic impact wrench. The latter does not deliver very precise torque so even after using it to tighten a fastener; you would need to finish the job with a calibrated torque wrench.
Some air impact wrenches can deliver up to 350 ft-lb, some 500 ft-lb and some much higher than that. Before you can buy an impact wrench, check the torque of the bolts that you will be working on.
Air impact wrenches can also loosen rusty bolts. To help you understand this better, here are three samples of pneumatic impact wrenches:
- The AIRCAT 1056-XL impact wrench has a 550 ft-lb of tightening torque and 750 ft-lb of loosening torque.
- The Ingersoll-Rand 2130 pneumatic wrench is 550 ft-lb of maximum torque.
- The NitroCat 1200-K Air Impact Wrench has a maximum of 900 ft-lb of torque. It also has 1295 ft-lb of loosening torque.
From these three air impact wrenches, you can see that the maximum torque differs a lot. You can buy what will help you meet your needs better and easily.
D) What is a pneumatic nut runner?
A pneumatic nut runner is another name for an air torque wrench. Just to reiterate what you might already know, this tool has a torque multiplier and the torque transfer is done through gears.
It runs on an air motor and it is powerful enough to tighten fasteners with high torque values.
The torque multiplier is a mechanism that lessens the impact of the work in progress. Therefore, less impact gets to your arms as you work, so you can do a lot of work with minimal effort.
These air torque wrenches work in the same way as the other torque wrenches. They are used on applications that require precise torque values.
You can use the air torque wrench in applications that require heavy-duty torque. In garages, it is used on truck wheel lugs. It is also used in the construction industry.
Since they use compressed air as their power source, you can use them easily in industries dealing with delicate products such as gas, oil, chemicals and others.
E) Advantages and disadvantages of a pneumatic torque wrench
Like any other tools, pneumatic torque wrenches have their pros and cons, but the benefits are more than the disadvantages.
Advantages
- Comes in stall torque and shut-off nutrunner designs with the latter going off at final torque
- Can use it on heavy-duty jobs with very little effort
- Can deliver a high amount of torque for heavy duty applications
- Accuracy level is within 3 to 5% if you calibrate it often
- Simple to use even for first timers
- Durable even when frequently used
Disadvantages of pneumatic torque wrenches
- Has many moving parts so the room for error is big
- Might require more frequent calibration if it is used heavily
- Costly to buy, since you also need air compressor
F) Best pneumatic torque wrench
There are so many air torque wrenches in the market. Here are five of them:
ITH nut runner type PDS
It has a nice reaction arm for stability
It has a flip switch to change the direction of rotation
Easy to set the torque using the air control valve
Comes with a heavy duty transport case
Torque output of up to 14000Nm/10,326 ft-lb
Ingersoll Rand 2235TiMAX
Has maximum torque of 1350 ft-lb
Has air rating of CFM (cubic feet per meter)
Minimal weight of 4.6 lb makes it easy to handle
Has a ½-inch drive
PTWA-40 Pneumatic Series
Delivers a maximum torque of 4000 Nm
Has a maximum speed of 7RPM
Delivers smooth and continuous torque with minimal impact on your arms
High accuracy rate of +/-4%
The weight of this pneumatic wrench is 12kg
Air Tool SA2508-81
This torque wrench is made in Taiwan
You will preset torque through the air control valve
Two speed rotation to meet different needs
Has a 1 to ½ -inch drive
Handle rotates to help you work in restrictive spaces
Final Thoughts on What Is A Pneumatic Torque Wrench
A pneumatic torque wrench is made for tightening heavy-duty fasteners with precision. When you start looking for one, do not mistake an air impact wrench for the air torque wrench because they look the same.
These wrenches have a high torque output of between 87.03 ft-lb and 35,108ft-lb. They run on powerful air motors and they deliver torque continuously.
You can find cheap as well as costly air torque wrenches, but if you will use it for heavy-duty work, do not sacrifice features for money.