By Joyce Laird, Contributing Editor
What is a non-locating bearing?
In many industrial applications there is a need for a bearing on each end of a shaft for radial support. “One must float free, however, there is also a need to locate the shaft in place axially; therefore one of the bearings must be fixed (on the shaft and in the housing),” Jon Reisterer, Application Engineer, NSK Americas, explains.
“Due to the fact that the temperature of machinery rises during operation, the components within them will undergo thermal expansion. The bearing opposite of the fixed (locating, held) bearing is the non-locating bearing (float, free). This non-locating bearing accommodates expansion of the shaft by sliding in the housing, sliding on the shaft, or in the cylindrical roller bearing – internally compensating by allowing relative axial movement between the inner and outer rings so that the bearing can float within itself.”
Non-locating does not always mean the same thing
The term non-locating bearing can be used in two related but different ways. Reisterer says that first, it could be referencing a bearing position in an application that needs to compensate for expansion, as explained earlier. “Secondly, would be to explain which bearing types are specifically designed to compensate for expansion;” he adds. The following combinations of locating/non-locating bearing arrangements are most commonly seen in industry:
A graphic view
Displacement between outer ring and housing (rotating inner ring) (right side of image in order).
- Deep groove ball bearing / deep groove ball bearing
- Spherical roller bearing / spherical roller bearing
- Matched set of angular contact ball bearings / deep groove ball bearing
- Axial movement of two rings relative to each other (left side of image in order)
- Deep groove ball bearing or angular contact ball bearing / cylindrical roller bearing
- NUP cylindrical roller bearing / NU cylindrical roller bearing (Figure 1)
- Double row angular contact ball bearing or matched taper roller bearing set / NU or N cylindrical roller bearing (flangeless inner or outer ring respectively)
As an example, Reisterer notes that a five foot long steel shaft rising from room temperature to 165°F during operation will grow in length by 0.04 inches, or 1 millimeter. “If both bearings are fixed, and not allowed to account for this growth, bearing life may be sacrificed due to additional loads on the bearings resulting from possible shaft bending where a non-locating bearing is not used.”
When in doubt as to what is the best fit for any specific application, it is wise to always consult with your bearing vendor for a suitable match. This can save time and cost when unsure of exactly what to use in any specific application,” he concludes.