Shaft Collars
The Shaft Collars is a cylindrical mechanical part that’s positioned on the rotating shaft and is an integral part of the sliding bearing.
Generally, the Shaft Collars and the bearing housing have an interference fit and a clearance match the shaft.
1, concept
A sleeve made of a full cylindrical protective shaft is named a Shaft Collar.
The bearing shell is equivalent to the external ring of the sliding bearing, the sleeve is integral and the opposite shaft is moving, as the bearing shell is segmented and the contrary shaft is rotating.
In the LEGOMindstorms series and BioTransRoSys group of robot components, the sleeves are specifically known as the silver-gray LEGO standard shaft holders, which are split into full sleeves and 1/2 sleeves.
The main materials of all kinds of Shaft Collarss on the major hydropower generating units are Cast Iron ZQAl9-4, ZQSn10-1 and ZQSn6-6-3.
2, the difference
A Shaft Collars is a sleeve on a propeller shaft or a yoke shaft. Bearings (referred to as “shafts” in Japan) are elements that fix and reduce the coefficient of friction of the load during mechanical transmission.
The similarity between the Shaft Collars and the bearing is that both bear the strain of the shaft.
The difference between your two is that the sleeve is of integral structure, and the relative movement between the shaft and the sleeve is when rotating; and the bearing is normally split, and the rotation is the relative movement of the internal and outer rings of the bearing itself. However in essence, the Shaft Collars is truly a sort of sliding bearing.
3, common factors behind damage
During the long-term procedure of the Shaft Collars, the top of journal is put through the pressing drive of the expansion sleeve and the composite mechanical power, that will cause its permanent deformation, and the size could be reduced by 0.1mm~0.3mm. Because of this, the mechanical expansion and the effectiveness of the force are not up to the required tightening drive, and a complementing gap occurs between the sleeve and the primary shaft, causing use of the sleeve.
4, the latest repair method
Due to the large worth 
of components, the original repair strategies are relatively expensive. With the advancement of advanced technologies such as polymer composite materials overseas, some repair methods with quick restoration and low cost are favored. This technique has also been presented in China, and the more mature Fushun Blue 2211F components. The material gets the extensive mechanical properties, excellent adhesion and temperature and corrosion level of resistance which cannot be compared with the traditional method. The utmost compressive strength can reach 1200kg/cm2, and the adhesion (overlap shear tensile check) is normally 225kg on the smooth steel surface. /cm2. Consequently, it can be used for the restoration of wear of large Shaft Collars parts. Furthermore, the equipment does not need to become disassembled in a large scale, which saves a whole lot of manpower and materials resources for the business.