Description of FAG super precision bearing speed and fit

FAG super precision bearings can be used at the highest speed. If grease lubrication is used, the speed index n dm can reach 2.0 106 mm/min, and if oil lubrication is used, it can reach 3.0 106 mm/min or even higher. Such high speeds generate high centrifugal forces that act on the inner ring to expand it. The expansion of the inner ring will cause its inner diameter to increase, affecting the fit between the inner ring and the journal. Possible consequences of this: Wear corrosion Inner ring slips on journal journal loss of guidance susceptible to vibration Possible eccentric misalignment reduces bearing performance. All of the above situations can be avoided by the tight fit of the bearing and the journal. The required interference can be calculated from Table 11 or by the BEARINX program. The value obtained by this method should still leave an interference of 1 μm at the highest speed. Interference increases preload, especially for rigidly adjusted bearings. This will result in increased heat generation in the bearing arrangement, affecting speed capability. Such increased preload must be compensated for by appropriate means. If fw n2 1.2 (red area in Fig. 11), it is best to consult Schaeffler Group Industrial Applications. The value fw can be obtained directly from Figure 12 (for B, HCB and XCB bearings) and Figure 13 (for HS, HC and XC bearings). If n2 fw 1.2 the resulting journal dimensions are as follows: Example: HCS71914E.T.P4S.UL Speed u200bu200bn u003d 16 000 min1 Actual dimensions of the inner ring: 70 mm 3 μm u003d 69.997 mm. (The size deviation of the inner ring is marked on the bearing ring). Hollow shaft with bore diameter of 35 mm (50 % of shaft diameter) fw u003d 4.30 109 (according to Figure 13 for HS, HC and XC bearings) n2 fw u003d 1.1 The value of 1.1 and the 50% curve of the hollow shaft (Figure 11) yields The required interference is 9 μm. Therefore, the actual size of the shaft should be 70.006 mm to ensure that the inner ring is still fastened to the shaft at a speed of n u003d 16 000 min1.