Which air impact wrench should you choose? A guide

Air impact wrenches are used to loosen and tighten screws without having to apply force. There are many different models on the market, so it is worth getting to know which air impact wrench will be best for a car mechanic, a tyre service or home use in your garage. Let's take a closer look.

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By Rafał Predko

September 8, 2021

7 min read

Air impact wrenches are used to loosen and tighten screws without having to apply force. There are many different models on the market, so it is worth getting to know which air impact wrench will be best for a car mechanic, a tyre service or home use in your garage. Let’s take a closer look.

How does an air impact wrench work?

Air impact wrenches work using compressed air systems, which put the wrench into motion, so you will also need an air compressor. The compressed air is forced into the cylinder of the wrench, and the rotor starts to rotate under the influence of the air inflow. The energy obtained in this way is transferred to the drive shaft, as well as to other elements of the tool.

The faster the motion of the air inside the wrench, the faster the rotor will turn, producing more torque. This type of solution, i.e. using compressed air, is generally safe. There is no sparking during use.

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Features of air impact wrenches

When considering which model to buy, start off by getting to know their basic features. The most important aspect to keep in mind is the torque. It determines the force with which to tool can be used, expressed in Nm. The torque also depends on other parameters of the compressor, so if you want it to be comparable to that stated on the specifications, make sure you use an efficient compressor.

And bear in mind that you will not always need to use the highest torque, which is why air impact wrenches are equipped with torque adjustment. Wrenches designed for professional use have up to a dozen or so levels to choose from, while home models usually have several. The more levels there are, the more universal the wrench. You can tighten different bolts using a different amount of pressure, without worrying about damaging them or not tightening them enough.

Another key parameter is the amount of air the wrench needs in order to work. It is expressed in litres per minute and is important in order to choose the right compressor for the wrench. As a rule of thumb, the capacity of the air compressor should be at least equal to that of how much air the wrench requires.

Another aspect worth paying attention to when considering which air wrench to buy is the noise level. Bear in mind that during use noise will also be generated by the tightened elements in addition to the work of the wrench itself. Regardless of the noise level, professionals usually use earplugs or hearing protection ear muffs, especially with intensive use, e.g. in a tyre service during high season.

Which compressor will suit your air wrench?

As already mentioned, in order to be able to use the air impact wrench you will need an air compressor. And for the compressor to work effectively, it will need to have an appropriate capacity and level of power. This is very important to keep in mind, so let’s return to this aspect for a moment. When considering which air compressor to choose, let’s start with the fact that the efficiency of the compressor should be greater than or equal to the air requirement of the wrench.

So, for example, for an air impact wrench with an air requirement of 410 l/min to work properly, you will need a compressor with a minimum capacity of 410 l/min. If you choose a less efficient compressor, the wrench will not reach its nominal power and work slowly.

So it is better to choose a slightly more efficient model. This way you will not only be sure that the wrench will work appropriately, but you will also be able to connect other air tools with a greater air requirement.

Different uses of air impact wrenches

Various air impact wrenches can be used for different purposes. They differ not only with regard to their technical specifications, but also price, so you should choose a wrench according to how you intend to use it as well as your available budget. Or course, for use in a professional car garage or tyre service you will need top quality tools, but for home use a less powerful, cheaper model should be sufficient.

Air impact wrenches for use in tyre services

Choosing an air impact wrench for use in a tyre service, make sure it has the highest possible amount of torque. You will use very intensively throughout the day, so the higher the torque the more efficient your work. In addition, greater torque, as well as a wide adjustment range, will make the tool more universal.

Before you make your choice, also pay attention to work comfort. Models with a composite casing are lighter than those with steel casing. This is important in the case of intensive use, as holding a heavier device can be tiring for your hands. Also, try to choose a robust and durable brand.

Air impact wrenches for home use

Air tools, due to their practical use, are also popular for use a home. They make it much easier change the wheels on your car, replace brake pads or even tyres. But if you are only going to use the tool for such purposes, and only from time to time, there is no point in investing in expensive, professional equipment. The situation is different when it comes to agricultural machinery, in which case you will need a professional air impact wrench with the highest possible torque.

When considering which air impact wrench to choose for use in your own home, it is worth also looking at the capacity of the air compressor. For home use a small compressor, with a capacity of 200 l/min and a capacity of 50 litres, should be more than enough. The same therefore applies to the wrench, which only needs to match the specifications of the compressor. However, the lighter the wrench the better, and at the same time it is safer to choose a model that is resistant to various types of damage.

How much pressure is needed for an air impact wrench?

Before buying such tools, many people wonder which air compressor will be appropriate, and how much pressure is needed. The answer in this case is simple – all air tools have a pressure requirement specified by the manufacturer. Using too much pressure will cause the components of the wrench to wear out very quickly. If the pressure is too low, the wrench will have less power, and therefore work less efficiently.

In order to obtain a constant working pressure, the compressor should ensure a sufficient air flow for all the tools connected to it.

What type of oil and lubricants should you use with an air impact wrench?

Air tools require the use of oil. Some more advanced air wrenches, with a torque greater than 1500 Nm, also require the use of lubrication. Oil is responsible for maintenance and lubrication of the main mechanical systems of the air wrench. The lubricant, on the other hand, ensures correct operation of the hammer mechanism.

Both products should be dedicated for air tools. Only in this way will you ensure proper oil adhesion, no negative impact on the materials used (aluminium, steel, rubber and plastic gaskets), as well as resistance to aging ensuring sludge does not form in the moving parts over time).

Which air impact wrench should you choose – summary

Which air impact wrench will be best for your needs depends on both the intensity of the work you intend to perform, and what you intend to use it for. For professional use in various types of workshops and mechanical services, you should aim for a wrench with the highest possible torque and a wide adjustment range. For home use a much simpler model will be sufficient.

In both cases, however, you should take into account that you will also need a suitable compressor, with a capacity at least equal to the air requirement of the wrench. So before making your final choice, compare the technical specifications of both of these devices.