A phenolic cage is machined from resin-bonded fabric laminate — sometimes called textolite or bakelite. It is light, strong, dimensionally stable and holds oil in the pores of the laminate, which is why it became the standard cage for high-speed spindle bearings. Its limit is temperature: about 120–150 °C depending on grade.
At 20,000 rpm the cage is centrifuged outward and its mass becomes a load on itself. Phenolic is roughly one sixth the density of brass, so the cage stays where it belongs. The laminate also absorbs a little oil and releases it into the pocket, which helps at the moment of starting when the oil film is thinnest.
Heat and moisture. Above its rated temperature the resin degrades and the cage loses strength; in humid or wet conditions the laminate absorbs water, swells, and the pockets tighten on the balls. Neither failure is gradual. In a spindle that has been stored in an unheated warehouse for a year, inspect the cage before fitting.
| Designations | T (SKF), TH (variant), sometimes TP |
|---|---|
| Material | Phenolic resin bonded to fabric laminate |
| Temperature | 120–150 °C depending on grade |
| Speed | The highest of any cage material |
| Weight | Lower than brass or steel |
| Lubricant retention | Good — porous laminate holds oil |
| Weakness | Absorbs moisture; brittle under impact; limited temperature |
| Typical use | Machine tool spindles, high-speed angular contact pairs |
| Criterion | Phenolic | Brass | Polyamide |
|---|---|---|---|
| Density | Low | High | Lowest |
| Max speed | Highest | Very high | High |
| Temperature | 120–150 °C | 250 °C | 120 °C |
| Oil retention | Good (porous) | Excellent | Moderate |
| Moisture | Absorbs and swells | Unaffected | Absorbs slightly |
| Cost | High | Highest | Low |
| Typical use | Spindle | Large roller | Appliance |
The default — cheap, strong, temperature-safe
Read →Machined brass — the high-end standard
Read →PA66 — quiet and cheap, 120 °C limit
Read →Two stamped halves joined by rivets
Read →One-piece snap-over retainer
Read →One-piece machined — for large roller bearings
Read →T designates a machined phenolic resin cage. TH is a variant used by some makers for the same construction.
No. Above about 150 °C the resin degrades. For hot positions use brass or a machined steel cage.
Usually moisture absorption followed by thermal shock, or an impact during mounting. Phenolic is strong in compression but brittle under impact.
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