Bearing selection is sometimes tricky as there are so many types of bearing available in the market like Deep Groove Ball Bearing, Angular Contact Ball Bearings, Self-aligning Ball Bearings, Spherical Roller Bearings, Roller Bearings, Taper Roller Bearings, etc. The selection of ball and roller bearings for a given installation depends upon the following factors:
- Load and the nature of the load, speed of shaft, expected life of the bearing and nature of environment where bearing is working.
- After considering the above factors, generally ball bearings are suitable for small machines running at high speeds while roller bearings are suitable for machines to be placed under heavy loads.
Let us now examine general selection criteria for each type of bearing:
- Deep groove ball bearings are normally used for radial and thrust loads. Thrust load can be up to maximum two-thirds of radial load.
- Angular contact ball bearings are designed to support combined radial and thrust loads or heavy thrust loads depending on the contact-angle magnitude. Bearings having large contact angles can support heavier thrust loads.
- Self-aligning ball bearings may be used for primarily radial loads where self-alignment ±40 is required. Extra care should taken while selecting these types of bearing as excessive misalignment or thrust load greater than 10% of radial load can cause early failure.
- Spherical roller bearings are excellent for heavy radial loads and moderate thrust. Their internal self-aligning feature is useful in many applications such as HVAC fans.
- Cylindrical roller bearings utilize cylinders with approximate length/diameter ratio ranging from 1:1 to 1:3 as rolling elements. Normally used for heavy radial loads and are especially useful for free axial movement of the shaft.
- Taper roller bearings are used for heavy radial and thrust loads. The bearing is designed so that all elements in the rolling surface and the raceways intersect at a common point on the axis thus true rolling is obtained. Where maximum system rigidity is required, the bearings can be adjusted for a preload.
- Thrust ball bearings may be used for low-speed applications where other bearings carry the radial load.
- Straight roller thrust bearings are made of a series of short rollers to minimize the skidding, which causes twisting, of the rollers. They may be used for moderate speeds and loads.
- Needle bearings have rollers whose length is at least 4 times their diameter. They are most useful where space is a factor and are available with or without inner race. If shaft is used as inner race, it must be hardened and ground. Full-complement type is used for high loads, oscillating, or slows speeds. Cage type should be used for rotational motion. They cannot support thrust loads