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2.2 Adjustments to Bearing Capacity

2.2.1 Raceway Hardness The capacities given in the dimensional table are valid only if all load carrying bearingcomponents are properly heat treated to a minimum hardness of HRc 58. The equivalent strength of material is approximately 300,000 psi. In applications without an inner ring, the shaft becomes an integral bearing component.If one or more bearing components possess a hardness of less than HRc 58, both dynamic andstatic capacities must be reduced by factors given in table 1. A hardness of less than HRc 40 is not recommended.The adjusted bearing capacities C’ and C’
O becomeAdjusted dynamic capacity: C’ = f
HD * C (5) RBC roller bearings without seals and metallic cages are heat stabilized and may be used atoperating temperatures between -40 Adjusted static capacity: C’
O = f
HS * C
O (6) ° F (-40 ° C) and +300 ° F (150 ° C) with no loss of capacity.Where applicable, temperature limits of seals, cage, and lubricant must be considered.Successful operation at higher temperatures requires a different heat treatment, whichreduces hardness proportionally. Alternatively, more temperature resistant bearing mate- rials can be substituted. Consult with RBC Engineering for recommendations and hothardness factors. 2.2.2 Operating Temperature
HardnessHardnessDynamicStatic HRc HV f HD f HS 58 655 1.001.00 56 617 .88 .99 54 580 .77 .97 52 545 .67 .94 50 513 .59 .90 48 485 .51 .85 46 458 .43 .76 44 435 .37 .68 42 413 .31 .60 40 393 .26 .55 Table 1. Capacity reduction factors 2.3 Thrust Capacity of Radial Cylindrical Roller Bearings Depending on internal design and operating conditions, cylindrical roller bearings cansupport considerable thrust loads, which makes them suitable for use as locating bearings. The main design criterion is the length to diameter ratio of the roller itself. Bearings equipped with roller lengths more than 2.5 times the diameter are called needle roller bearings and should not be used to support thrust loads.The maximum permissible thrust load is given as a percent of the actual radial load appliedand depends on speed and lubrication conditions. It is generally safe to allow a dynamic thrust load equal to 10% of the radial load. 17