As the method of mounting can affect the accuracy, life, and performance of a bearing, it requires close attention. The bearing’s characteristics should be thoroughly investigated, and mounting should be done in the proper way. The handling procedures for bearings should be fully studied by design engineers such that standards can be established regarding: cleaning of the bearings and associated parts, checking of dimensions and finishes of related parts, mounting, inspection after mounting, and supply of lubricants.
Bearings should remain packed until immediately prior to mounting, and when using ordinary grease lubrication, the grease should be packed in the bearings without cleaning them first. Even in instances of standard oil lubrication, the bearings do not need to be cleaned. Despite this, bearings for instruments or high-speed applications must be cleaned with clean, filtered oil to ensure the removal of anti-corrosion agents.
After the bearings are cleaned, anti-corrosion material should be reapplied. For pre-lubricated bearings, no cleaning is necessary. Bearing mounting methods depend on the bearing type and type of fit. Because bearings are commonly used in rotating shafts, the inner ring requires a tight fit. Bearings with cylindrical bores are typically mounted by pressing them on the shaft, a method called press fit, or by heating them to expand their diameter, in a method called shrink fit. Bearings with tapered bores can be mounted directly on tapered shafts or on cylindrical shafts using tapered sleeves.
Bearings are typically mounted in housings with a loose fit, though in cases where the outer ring has an interference fit, a press may be used. Another way bearings can be interference-fitted is by using dry ice to cool them before mounting. However, to use this method, a rust-preventative treatment must be applied to the bearing as moisture in the air condenses on the bearing’s surface.
Methods for Mounting Bearings
There are many different methods for mounting bearings. As stated, for bearings with cylindrical bores, there are two methods: press fits and shrink fits. Press fitting is primarily done to small bearings. In this process, a mounting tool is placed on the bearing’s inner ring and the bearing is slowly pressed onto the shaft until the side of the ring rests on the shoulder of the shaft. Because press fitting requires significant force, shrink fitting is a commonly-used alternative method. In shrink fitting, the bearings are first heated in oil to expand them prior to mounting. This allows them to be installed without excessive force and promotes faster mounting.
If a bearing has a tapered bore, rather than cylindrical, they are often mounted using hydraulic pressure. Holes are drilled in the sleeve which are then used to funnel oil under pressure to the bearing seat. As the bearing expands radially, the sleeve is inserted axially with adjusting bolts. When a large bearing is mounted on a shaft, the outer ring is sometimes deformed into an oval shape by its own weight. Additionally, if the clearance is measured at the lowest part of the deformed bearing, the measured value may be bigger than the true value. This can lead to the interference fit becoming too tight and residual clearance being too small.
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