1. The taper angle difference of the adapter sleeve must be precise. The national standard uses △D1mp-△d3mp to represent this. The allowable tolerance for different size ranges is +0.018-0.09, with an upward bias. The taper angle difference of the adapter sleeve must be large, not small. This means the large end must have proper contact, while the small end of the taper can have a slight gap. If the taper hole fits poorly, the matching self-aligning roller bearing will experience stress on a single row of rollers, resulting in unstable operation, high vibration, loud noise, easy loosening, and short bearing life. The taper angle difference of a high-precision adapter sleeve should be ≤0.005, ensuring a contact area of not less than 90%.
2. The radial runout (commonly referred to as wall thickness difference) between the outer taper surface and the inner hole of the adapter bushing must be highly precise. Otherwise, the rotating shaft will experience centripetal force due to the unevenness, resulting in unstable operation, high vibration, and loud noise. An ideal wall thickness difference is "0". The maximum clearance value for bearings with an inner diameter of 65 mm or less, as specified in the national standard, is approximately half the maximum clearance value for that bearing specification group. This is very close to the maximum clearance value for Class C precision. Therefore, national standard-compliant adapter sleeves are unsuitable for use in precision-grade, high-load bearings.
3. The straightness of the outer conical surface and inner bore of the adapter sleeve must be good, meaning good form and position tolerances and good cylindricity accuracy. The national standard does not specify that any single cross-sectional dimension being within the tolerance range is sufficient for compliance. This leads to lax control over the straightness of the outer conical surface, especially in the case of grinding. Poor straightness of the blank itself, coupled with inadequate grinding wheel dressing, results in very poor surface straightness. Since most companies lack profilometers for inspection, this aspect is a significant problem in my country's adapter sleeve industry, severely affecting the precision and stability of the fit, ultimately leading to poor bearing performance.
4. The locking function of the adapter sleeve is achieved by rotating the locking nut axially and pressing the end face of the bearing inner sleeve, which causes the adapter sleeve and the inner hole of the bearing to be tapered and compressed, thus fixing the bearing on the rotating shaft. Therefore, the thread fit between the bearing nut and the adapter sleeve must be good and meet the national standard requirements for ordinary threads.
