Steel is the default cage material for the majority of the world's bearings. Stamped from sheet steel, it is light, cheap and unaffected by the temperatures that destroy polyamide. Machined steel cages are used where the stamped version would distort — large bearings, high speed, and heavy roller types.
A stamped cage is folded from sheet, with pockets punched and the two halves riveted or interlocked. It is light — which matters because cage mass is what limits speed — and it is cheap. A machined cage is cut from a solid ring, so it is heavier but far stiffer and better balanced. Above roughly 5,000 rpm on a medium bearing, or in any large roller bearing, the stamped cage starts to be the limiting component.
Steel has no softening point in the bearing's working range, is compatible with every common grease and oil, and does not care about the additives that attack polyamide. When a bearing fails at temperature, a steel cage usually survives long enough to show you what actually happened — which is diagnostically useful.
In water, steel cages corrode and swell, which can jam the rolling elements. In applications where weight matters — high-speed spindles — a steel cage adds inertia that a phenolic cage avoids. And in very quiet small motors a steel cage transmits more noise than polyamide.
| Stamped designation | J (SKF, FAG), SP (window type), JN (inner-ring centred) |
|---|---|
| Machined designation | F (SKF machined steel) |
| Temperature | 150 °C stamped, up to 250 °C machined |
| Speed | High — no softening point |
| Lubricant compatibility | Universal |
| Cost | The lowest of all cage types |
| Weakness | Stamped cages distort above very high speed; steel corrodes in water |
| Typical use | General ball and roller bearings, motors, gearboxes, pumps |
| Criterion | Steel | Brass | Polyamide |
|---|---|---|---|
| Temperature | 150–250 °C | 250 °C | 120 °C |
| Speed | High | Very high | High |
| Weight | Low (stamped) | High | Lowest |
| Quiet running | Moderate | Moderate | Best |
| Cost | Lowest | Highest | Low |
| Chemical resistance | Poor in water | Good | Attacked by some additives |
Machined brass — the high-end standard
Read →PA66 — quiet and cheap, 120 °C limit
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 →J is the standard designation for a stamped steel cage, ball-centred, used by SKF, FAG and most European makers. Japanese catalogues often leave the cage unmarked when it is stamped steel.
At temperature, yes — polyamide stops at about 120 °C. At noise and cost, polyamide is better. It depends which limit binds first in your application.
Yes. In wet or washdown applications a steel cage can corrode and jam. Brass or a sealed bearing with proper grease coverage is safer.
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