super precision bearings

DEFLECTION AND RIGIDITYDeflection and RigidityHigh running accuracies even underalternating loads can beachieved with zero-clearance bearingarrangements. They arearranged and preloaded dependingon the load and required rigidity.The rigidity can be increased bymounting bearing sets.Bearing Arrangement Suffix S a ’ K aEα = 15° and α =25°N/µm NDB S1)a 3 · F VTBT 1.64 · S a 6 · F VQBC 2 · S a 6 · F VQBT 2.24 · S a 9 · F VSpindle BearingsThe axial rigidity values stated inthe bearing tables apply to bearingpairs in back-to-back or face-tofacearrangement. The radial rigiditycan be estimated from the axialrigidity by means of a factor.S r ≈ 6 · S a for α = 15°PBC 2.64 · S a 9 · F VK aE = Unloading force F V = Preloading force1)Bearing tables35: Axial rigidity S a ’ of a bearing set at a centrically acting axialloadBearing Arrangement Suffix S r ’N/µmS r ≈ 2 · S a for α = 25°DBS rSets of more than two bearingsfeature increased rigidity values.Table 35 shows the determinationof the axial rigidity at a centricallyacting axial load. The radial rigidityfor such sets with a radial load actingon the centre of the set is calculatedaccording to Table 36.QBCTBT2 · S r1.36 · S r36: Radial rigidity S r ’ of a bearing set; the radial load acting on thecentre of the setFAG · 176