Bearings and Lubricants

Cylindrical Bearings

Cylindrical roller bearings have high radial capacity. These bearings feature low friction, which permits operation at high speed, and thrust loads of some magnitude can be carried through the flange-roller end contacts.

Although the rolling elements are called "cylindrical," they are not true cylinders. True cylinders would produce stress concentrations at the ends of the roller-race contact, resulting in high wear and high sensitivity to misalignment. Instead, rollers are usually crowned or end relieved.

Because they are used for high speeds, cylindrical roller bearings are commonly made in precision grades such as RBEC5 as well as the lower grades. The close tolerance of the higher grade bearings may be needed in precision spindles as well as in high-speed applications.

Unlike ball bearings, cylindrical roller bearings are generally lubricated with oil; most of the oil serves as a coolant.

A persistent problem in high-speed, lightly loaded, cylindrical roller bearings is roller skidding, which can lead to premature bearing failure. One technique to combat skidding is an out-of-round raceway, which pinches the rollers at two diametrically opposite points. Another technique is the use of two preloaded hollow rollers. Both techniques require precise engineering to eliminate loading without introducing other problems.

Nonlocating Bearings - These bearings have either a separable outer ring or separable inner ring and allow considerable axial movement of the shaft. The bearings must be used with an axially locating bearing such as ball bearings. Nonlocating bearings have high radial and load capacity, high stiffness, and the highest speed capability of any roller bearings.

Cylindrical Bearings