NKE Hauptkatalog / General Catalogue 2011

Selection ofBearing Type and SizeA particularly good compensation of misalignmentsis allowed by the self aligning bearingtypes, such as self aligning ball bearings,spherical roller bearings and thrust ball bearingswith spheroid housing washers. Single row deepgroove ball bearings, for example, allow accordingto their individual operating clearance, angularmisalignments up to 10 angular minutes.The most frequently used bearing types in preloadedbearing arrangements are angular contactball bearings (fig. 6.18) and tapered roller bearings.In case of single row cylindrical roller bearingsthe maximum permissible amount of angularmisalignment is limited from 2 up to 4 angularminutes.Several bearing types do not permit any misalignment.In all these cases a misalignment generateshigher bearing internal forces on rolling elementsand raceways, thus reducing bearing fatigue life.For more detailed information on the individualcapacity of each bearing type to accommodatemisalignments see specific product informationpages.RigidityThis term describes the magnitude of (elastic)displacement of a rolling bearing under load.Fig. 6.18For detailed information see chapter “BearingClearance” page 319.The elastic deformation is very small andtherefore will not play any role in the majority ofapplications.Only in specific applications, such as machinetool applications which demand a very stiff, rigidbearing arrangement, such displacement requiresconsideration.In general, bearings with line contact such asroller bearings provide higher rigidity comparedto ball bearings. The stiffness of a bearingarrangement can be improved by applyingpreload to the bearings.www.nke.at 281