Roller Bearings

Roller bearings are used in rotary applications to replace sliding movement with low friction, rolling motion. The principal types of roller bearings are cylindrical, spherical, and tapered. In general, roller bearings offer higher load capacities than ball bearings of the same size.

Tapered roller bearings consist of four basic components including the cone (inner ring), the cup (outer ring), tapered rollers, and a cage (roller retainer).  Under normal operating conditions, the cone, cup and rollers carry the load while the cage spaces and retains the rollers on the cone.  The cone, rollers and cage are referred to as the cone assembly.  The cup is usually separable from the cone assembly facilitating machine assembly.  Cup and cone assemblies come in a variety of configurations such as single-row, two-row, four-row and thrust bearing assemblies.  Tapered roller bearing assemblies may be made with optional configurations including spacers and closures. 

Materials used for roller bearings are typically alloy or low carbon steels.  Some applications require case or thoroughly hardened high carbon bearing quality steel.  Depending on the size of the bearing to be produced, appropriate quantities of alloying elements are added to the steel melt to assure optimum properties in the finished product.

When low carbon carburized grades of steel are used, carbon is often introduced into the surfaces of the roller bearings components after machining; to a depth sufficient to produce a hardened case that will sustain bearing loads. The carbon and alloys added earlier ensure a proper combination of hard fatigue resistant case and a tough ductile core.  High carbon grades of steel do not require carburizing and are either case-hardened, normally by induction heating, or through-hardened by conventional heating methods. 

Another benefit derived from case carburizing tapered roller bearings is the development of residual compressive stresses in the surface layers.  These residual stresses retard the propagation of fatigue cracks that initiate close to the bearing raceway and roller surfaces.  This helps to improve the bending fatigue resistance at the large rib undercut and ensure the ability to endure heavy shock loads without damage.  The hardened case of roller bearings components provides fatigue resistance and the ductile core provides toughness for the roller bearing.

The bearing setting of a roller bearing is defined as the specific amount of either endplay or preload.  Tapered roller bearings have the inherent advantage of being adjustable; therefore, they can be set to approach optimum performance in almost any application.  They may be set manually, supplied as a preset assembly, or set by using an automated setting technique.  Automated roller bearing setting techniques offer many advantages such as reduced setting time, decreased assembly cost, and consistent and reliable setting with minimal skill requirements.  They may be applied to both assembly line and field repair applications.

Selection of roller bearings consists of two steps.  First, one must determine the desired bearing life and then select the roller bearing with a sufficient basic dynamic load rating to meet that life requirement. 

Roller bearings are used for heavy-duty moderate-speed applications.  Potential applications for spherical and cylindrical roller bearings include power generation, oil field, mining and aggregate processing, wind turbines, gear drives, rolling mills.  Single-row tapered roller bearings are used in such applications as machine tool spindles, gear reduction units, automotive transaxles, transmissions, vehicle front wheels, differential and pinion configurations, conveyor rolls, machine tool spindles and trailer wheels.

• Hollow Roller Bearings
  Hollow roller bearings are single-row or double-row radial bearings with an inner ring, an outer ring, and hollow or thin-wall rollers. The thin wall in the rollers allow the bearings to be preloaded,...
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• Double-Row Tapered Roller Bearings
  Two-row or double-row tapered roller bearings have increased radial load capacity compared to single-row bearings. They can also handle thrust loads from both directions. The rollers can be configured...
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• Spherical-roller bearings graduate to a new class
  Advances in materials, design, and processing have combined to triple bearing life. EDITED BY KENNETH J. KORANE Explorer bearings are available in both sealed and unsealed versions, and are...
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Part Numbers for Roller Bearings