A polyamide cage is moulded from glass-fibre reinforced PA66. It is light, quiet, self-lubricating against steel and cheap to produce, which is why it is the standard cage in appliance motors, fans, small gearboxes and automotive accessories. Its limits are temperature and chemistry, not speed.
The material is softer than steel and dampens the impact of the balls against the pocket walls. In small motors, where the bearing is the dominant noise source, that damping is worth several decibels. It also weighs a fraction of brass, so it does not centrifuge outward at speed.
Polyamide does not degrade gradually. It reaches a glass transition, softens, and the pockets lose their shape — after which the cage no longer spaces the balls and the bearing fails quickly. There is no useful warning. If the position can reach 120 °C in a fault condition (blocked filter, failed fan, overload) the cage is a latent failure.
Polyamide is attacked by ammonia, by some refrigerants and by certain extreme-pressure grease additives at temperature. In refrigeration compressors and in plants using ammonia-based cleaning, a polyamide cage is a known failure. Brass or steel is the safe substitute.
| Designations | TN9 (SKF), TVP (FAG), P (NSK), TN (generic) |
|---|---|
| Material | Polyamide 66 with 25–30% glass fibre |
| Temperature | −40 to +120 °C continuous, 100 °C in oil |
| Speed | High — low mass, low friction |
| Noise | The quietest common cage |
| Weakness | Softens above 120 °C; attacked by some additives |
| Cost | Low |
| Typical use | Appliance motors, fans, small gearboxes, automotive |
| Criterion | Polyamide | Steel J | Brass M |
|---|---|---|---|
| Temperature | 120 °C | 150 °C | 250 °C |
| Noise | Best | Moderate | Moderate |
| Mass | Lowest | Low | High |
| Cost | Low | Lowest | Highest |
| Chemical resistance | Poor to ammonia and refrigerants | Good, poor in water | Good |
| Speed | High | High | Very high |
This category covers everything outside the standard catalogue: thin-section and miniature bearings,…
Read →A self-aligning ball bearing carries two rows of balls running on a common sphered raceway in the outer…
Read →A deep groove ball bearing is a single-row rolling bearing in which a ring of balls runs in deep raceway…
Read →An angular contact ball bearing has its raceways offset so that the line joining the contact points crosses…
Read →A cylindrical roller bearing uses cylindrical rollers in line contact with the raceways, which gives a high…
Read →A tapered roller bearing uses conical rollers running between conical raceways whose apexes meet on the…
Read →The default — cheap, strong, temperature-safe
Read →Machined brass — the high-end standard
Read →Resin-bonded fabric — highest speed
Read →Two stamped halves joined by rivets
Read →One-piece snap-over retainer
Read →One-piece machined — for large roller bearings
Read →TN9 is SKF's designation for a moulded polyamide cage, glass-fibre reinforced, ball-centred. FAG writes TVP for the same construction.
Above about 120 °C continuous. The material softens rather than degrading slowly, so failure is sudden.
Usually not. Ammonia and several refrigerants attack polyamide. Brass or steel cages are specified for that duty.
Yes. Its low mass is an advantage at speed — the limit is temperature, not rpm.
Send the designation, the three dimensions and the quantity — we reply with price, brand options and lead time within 30 minutes on working days.