Spindle Contamination and Sealing Options

Spindle failure caused by contamination is all too common across all industries. Here we will review sealing options followed by a few tips on how to prevent contamination of your business critical machine tool spindles.

Contact seals work the best whereever you can implement them. Unfortunately they wear out and need exchanged regularly. They will not work in High Speed applications due to heat generation caused by friction (rotating surface contact).


click to enlarge

click to enlarge

Labyrinth seals work well in high speed applications but are vulnerable to contamination by design and require strict attention to environment to perform to their peak. They are cost-friendly and maintenance-free.

Air sealing systems are a labyrinth seal upgrade. They provide better sealing in the same high speed application. Positive air pressure is forced  through the labyrinth seal from the interior of the spindle to the outside to prevent penetration of contaminants.

Custom seal systems are available in different variations. Most of them have certain applications in which they work best. The spindle repair experts can upgrade your current seal system or implement a new system better suited to your application. Sometimes a combianation of sealing systems will be required to achieve the desired result.

If you have problems with contamination entering your machine tool spindle, check the following:

  • coolant spray should not aim directly at spindle nose
  • coolant spray is off when spindle is off
  • do not use compressed air around the spindle seal system while cleaning machine, this can blow particles into the nose of the spindle
  • if you run sealing air, keep the air pressure flowing until spindle has cooled, otherwise the spindle cooldown will   cause a vacuum which can suck the contaminants into the spindle bearings.
  • make certain that your seal system is maintained properly (depending on type of seal) i.e. – air seal needs   to run filtered and dried air!! contact seal might need re-lubed frequently to prevent wear, etc.
  • make sure that labyrinth seals that have drains are actually draining and not plugged by contaminants, or     pointing upward due to faulty installation, and ensure that coolant is not aimed directly at drain holes


  • What is the recommended air pressure to provide for an air assisted labyrinth seal?

    On my little 1HP 62mm spindle 20PSI seems to little, but on my larger 2HP 80mm spindles 20PSI really seems to use the air.

    I’ve been told by non-authoritative sources that I should run from 15-20 PSI. 15 didn’t “feel” like it was enough on my smaller spindle.

    I high speed cut aluminum and flood coolant is the norm. (SC520 and water.)

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