Products Precision & Commercial Ball Bearings

Precision & Commercial Ball Bearings

Ball bearings carry radial and axial loads, minimize friction, and are used to support and position rotating components. While the ball bearing concept predates Leonardo da Vinci, its design and manufacture have significantly progressed. Commercially available ball bearings are typically made from hardened steel, but other materials include stainless steel for improved corrosion resistance and ceramic (balls) which can achieve high radial speeds.

Ball bearings are made up of balls which are secured into a cage to keep them in place while allowing them to freely revolve. In both the inner and outer races, the balls are contained inside channels. Ball bearings have a lower load capacity for their size than other bearings due to the lack of surface contact between the balls and races.
Figure 1 Typical High-Speed Ball Bearing

Figure 1 Typical High-Speed Ball Bearing

A typical deep-groove ball bearing designed for high-speed operation is shown in Figure 1.
Deep-groove bearings are made to withstand both radial and axial loads.

In this bearing, the separator serves to keep the balls from rubbing against one another as it is piloted on the inner race O.D. Alternatively, the separator may be piloted by the rolling elements or by the outer race I.D. Where rotative speeds are low, the separator often is omitted. The rolling elements may take many forms — cylinders, balls, tapered rollers, barrels, or very slim rollers known as needles — and the whole bearing name is generally taken from this form.

Ball Bearings

There are several types of ball bearings that fit specific needs. The deep-groove ball bearing, Figure 2(a), is the most versatile. Radial loads and thrust-load capacities may be approximately equal in this bearing. When it has the proper separator, it is very good for high-speed operation. At low speeds, no bearing separator is required; at intermediate speeds, a ball control separator of steel-ribbon construction is adequate; while the ultimate high-speed performance is obtained with a race controlled (or piloted), fully machined separator.

Since balls are assembled into the bearing by eccentric displacement of the races the number of balls in this type of bearing is limited. More balls can be introduced into the bearing if a notch is machined into one of the races, Figure 2(b). Radial load capacity is higher in this bearing than in the standard deep-groove construction, but high-speed performance and thrust-load capacity is impaired. When large thrust loads in one direction are coupled with radial loads, angular contact ball bearings, Figure 2(c), are usually superior. Most high-speed and precision spindles use axially preloaded pairs of these bearings. Preload is controlled by the length of the spacers, which determine axial location of the races, or by mounting the bearings against one another in a "back-to-back" or "face-to-face" fashion. The double-row, angular-contact bearing, Figure 2(d), is a simpler arrangement from the standpoint of the user. The preload is built into the bearing at the factory.

In contrast the previously discussed bearings, in which alignment is a very critical item, the self-aligning ball bearing, Figure 2(e) by virtue of the spherically ground outer race can tolerate considerable misalignment of shaft and housing. On the other hand, load-carrying capacity is reduced due to the high contact stresses that result from the large difference in curvature between the balls and the outer race.

The thrust ball bearing, Figure 2(f), is adaptable to large thrust loads that have almost no radial component. Very large sizes of this bearing are used in gun turrets and large earth moving machinery.