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Bearing data – general Cages + 125 °C. If the operating temperaturesare higher, the bearings must be subjectedto a special heat treatment (stabilisation) so that inadmissible changes in dimensions donot occur as a result of structural changes inthe steel. However, the bearings should notbe stabilised for a highertemperature thanthe expected operating temperature.As the load carrying capacity of bearingsdecreases with increasing temperature, thebasic dynamic load rating C should be mul-tiplied by an appropriate reduction factor,see following.Bearing Various cage types and designs are used for the different types and sizes of SKF needle roller bearing types; the cages differ as to form, material, manufacturing methods, cost of production and operational limits. The standard cage for a particular bearing is not identified in the bearing designation unless it is of polyamide.With reference to the viability of produc-tion, the costs and the different applicationareas of the bearings, the standard cage forthe larger bearings may be different fromthat for the smaller bearings in one and the same series.In the introductory text to each table section information is provided regardingthe standard cages with which the bearingsare fitted and also the possible alternatives.Polyamide cages Small and medium-sized bearings are fittedwith moulded cages of heat-stabilised, glassfibre reinforced polyamide 6,6 as standard.This material is characterised by a favour-able combination of strength and elasticity.The good sliding properties of the plastic on lubricated steel surfaces and the smooth-ness of the cage surfaces in contact with therolling elements mean that little friction isproduced by the cage so that heat genera-tion and wear in the bearing are at a min- imum. The low density of the material means that the inertia of the cage is small.The injection moulding process used to pro-duce the cages allows functionally suitabledesigns to be realised. The excellent runningproperties of polyamide cages under lubric-ant starvation conditions permit continued operation of the bearing for a time withoutany risk of seizure and secondary damage.When using bearings with polyamide cages the permissible operating temperat-ures for the material and its resistance to the lubricant used must be observed. At operat-ing temperatures up to the values given in

Needle roller bearings (4703 /IE) - 5564 Materials

Bearing rings and rolling elements The rings and rolling elements of SKF needle roller bearings are made of a through-hardening carbon chromium steel to DIN 17 230:1980 containing approximately 1 % carbon and 1,5 % chromium. The thin- walled deep drawn outer rings of drawn cup and alignment needle roller bearings are exceptions to the above and are made of mild steel to DIN 17 230:1980.All components are hardened and can generally be used at operating temperaturesup to Table for the various oils and greaseswhich are used as bearing lubricants, cageproperties are unaffected. If the permissible temperature is exceeded, the cage materialwill age, this process being accelerated thelonger the cage is exposed to the excessive temperature (°C) 150200250300 Reduction factor1,000,900,750,60
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