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Pneumatic motor maintenance tips every on-site machinist needs to know


Flange facing machines and many other portable machine tools in the Mirage range can be specified with a pneumatic drive option. Where a compressed air-line is available, these motors provide a simple, cleaner and safer solution than their hydraulic and electric equivalents.

When used and maintained correctly, you can expect a high level of performance from your pneumatic motor for many years. But what are the best practice things you should carry out to make sure your portable machine tool works efficiently every time?

Many of the machines from Mirage use air motors manufactured by Modec. You can find good advice available to download from their website here, but for your convenience we’ve summarized their advice below:


The oil used to lubricate an air motor must be liquid enough to work in very low temperatures. The motor is constantly producing cold air, so the viscosity and technical characteristics of the oil are critical. Correct lubrication will also reduce the effects of humidity inside the motor which by minimizes the effects of corrosion.

What happens if the wrong type of oil is used?

If the wrong oil is used there is a risk that it won’t sufficiently lubricate all of the necessary parts within the motor. After some time, the performance of the motor will suffer through reduced speed or start torque, and potential damage to the motor’s blades or the cylinder. An oil with a grade of SAE 10 will be relevant in many situations.

How should the oil be applied?

A small amount of oil is sprayed inside the motor along with the air supply, but if the machine has been standing idle for a long time you should apply a few drops directly into the inlet before starting it up.  Also, when the motor has been running continuously for a long period, it’s a good practice to make sure the motor runs for a few seconds with properly lubricated air. This will help to create a protective oil film on the internal parts.


Above: A typical air filter and lubrication unit for connection to a pneumatic motor.



If small particles of dust or metal get into the motor, they can cause damage to the blades and destroy the surface finish of the cylinder. This can be prevented by installing a filter system immediately before the point where the air enters the motor.

What could happen if dust and hard particles get inside the motor?

Damage caused by particles can reduce motor speed, torque and therefore the motor’s power output. Replacing a filter is easy to do and will be much cheaper than replacing a damaged cylinder.


  • Assess the amount of machining time that you use the motor for. The running time used should be long enough for the oil to lubricate the motor.
  • If the machine won’t be used regularly, make sure there’s plenty of oil inside the motor. This will help to protect against corrosion, especially in humid environments.
  • The weight and load the motor is subject to will affect its use. If too much load is applied the motor will stall before it can cause much harm. But watch out for strong vibrations, as these have an impact on the motor components.  Bear in mind that a pneumatic motor used under constant vibration will have a much shorter lifespan.


 If you suspect there’s a problem with the air motor, carry out these checks to discover the root cause of the problem;

  • Check the air from the exhaust - one easy check is to hold a tissue or dry cloth to the motor’s exhaust and look for signs of oil. If the lubrication levels are correct you will see evidence of oil. If you don’t see any oil, check there’s plenty in the reservoir and then check the lubrication levels. If there’s still no evidence of oil when you test again there’s clearly a problem with the lubrication system. Another tell-tale sign of a potential problem is if there’s water on the tissue.
  • Check the air filter - Is it blocked with particles?
  • Check the rotor is turning freely - If this is running freely this suggests a problem before the pneumatic part. Check the air supply and air connections. If the motor is not running freely then the problem will be inside the motor and the chances are the bearings, blades or cylinder may be damaged.


Each customer should consider the nature of the jobs it will be used on. Especially the working environment. Design your own maintenance schedule that takes these factors into account.

  • Irregular usage – get into the habit of running the motor for 2 – 3 minutes with maximum lubrication.
  • In cold conditions – In very cold environments, make sure the oil lubricator doesn’t freeze. You should also watch that the additional cold generated by the motor doesn’t reduce the external temperature any further. This could cause humidity in the air to freeze and block the exhaust apertures.
  • In humid conditions – Where humidity levels are high, the motor will need extra lubrication to protect against corrosion, especially before the machine is stored away.
  • Under-water – when using stainless steel motors under water, check the seal around the exhaust is completely waterproof. Just a the smallest of leaks will result in zero performance!


BY now you will have worked out that it’s all about filtration and lubrication. Keeping on top of these two areas is inexpensive and prevents the need for more expensive replacement parts at a later date. Filters, bearings and blades are relatively cheap to replace, but if the rotor, end plates or the cylinder need replacing, each of these could cost as much as half the price of a whole new motor. 

Think of your own car. If you don’t top up the oil regularly you will probably end up paying much more in the long run!

Do you need equipment for an on-site machining project? Visit our resources section to download our buyers guides or get in touch with your regional contact here

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