Bearing rating life — L10 (ISO 281)
Estimates basic rating life from the dynamic load rating and the applied load.
Use the same force unit for C and P (e.g. both in N). L10 is fatigue life at 90% reliability; it does not account for lubrication, contamination or misalignment (the ISO 281 modified life Lnm adds those). Reliability factors follow ISO 281:2007; some older references use slightly different values (e.g. 0.62 / 0.21).
Shaft & housing fit recommender
Suggests ISO 286 tolerance classes from the load conditions. The key rule: the ring carrying a rotating load needs an interference fit.
Guidance for solid steel shafts and cast-iron/steel housings with normal-clearance ball bearings. Use one grade tighter (grade 5, e.g. k5) for high running accuracy, and tighter still for hollow shafts, thin-wall or light-alloy housings, and heavy vibration. A tighter fit reduces internal clearance — consider C3 to compensate. Confirm exact grades and µm values against ISO 286 and the catalogue.
Speed check — n·dm screening
A first-pass check of whether a speed is sensible for the bearing size and lubricant, using the speed factor n·dm.
dm = (d + D) / 2; speed factor = n × dm. The limit field is pre-filled with an indicative guideline for the type and lubricant — replace it with your catalogue's speed-limit factor for an accurate check. As a rule, scrutinise any speed above 80% of the limit. This screens the speed factor only; always verify the catalogue limiting speed for the specific bearing.