Oil inlet angle for larger alignment tolerances
The oil inlet of the UC type bearing is provided on the outer ring at an inclination of approx. 10°. Thus, the oil groove in the bearing housing can be located closer to the center of the bearing. Therefore, the resultant tolerance for alignment is as large as ±2°, as shown in Fig. A (in the case of narrower outer ring type, ±1°). Since the oil inlets of other manufacturers' bearing units are oriented vertically, the oil groove is inevitably located near the end face of the bearing housing, as shown in Fig. B. Thus, the distance between the fitting face of the bearing and that of the bearing housing leads to the relationship a > b (a=NTN, b=other manufacturers), and the alignment tolerance of other manufacturers' bearing units is smaller than that of NTN bearing units.
Self-aligning cover seal
NTN covered bearing units are designed so that the seal lips can follow the shaft even when it is misaligned. Therefore, the covered bearing unit can achieve the rated dust-proofing performance of the cover seal even when the bearing is self-aligned to the shaft angle. However, to ensure that rated dust-proofing performance is not compromised due to uneven contact between the seal lips and the shaft, the alignment tolerance should be limited to ±1°. Since the seals of other manufacturers' products are fixed, dust-proofing performance becomes unreliable when the bearing is aligned with the shaft angle.
*Diagram shows a cast iron cover; the same method of alignment applies to a steel plate cover.