Description

Ceramic hybrid bearings, the most common type of ceramic bearing, are constructed of steel inner and outer rings with ceramic (typically Si3N4) balls in place of steel. Common types of ceramic bearings are angular contact and conrad.  Ceramic bearings containing all ceramic balls are also nonconductive and are commonly used in electric motor applications.

Types

Ceramic hybrid bearings, the most common type of ceramic bearing, are constructed of steel inner and outer rings with ceramic (typically Si3N4) balls in place of steel.

Other common types of ceramic bearings are angular contact and Conrad. These bearings have several advantages over all steel bearings, such as:

• Higher speed and acceleration capability
• Increased stiffness
• Higher accuracy
• Lower friction and heat generation
• Reduced lubrication requirements
• Low thermal expansion
• Extended operation life

Specifications

The bearing industry uses a standard number system for bearings with metric diameter bores. For bore sizes 04 and up multiply by 5 to obtain the bore in millimeters. If the bore is a hex this refers to the dimension across the flats. If the bore is tapered this refers to the smaller diameter. 

The outside diameter of the bearing includes the housing if a housed unit, but excludes the flange if a flanged bearing. 

The outer ring width is the overall width of the outside of the bearing. The outer ring width is the overall width of the outside of the ring.

The rated speed for a bearing running with grease lubrication is lower than a bearing with oil lubrication.

The dynamic axial or thrust load is the calculated constant axial load, which a group of identical bearings with stationary outer rings can theoretically endure for a rating life of 1 million revolutions of the inner ring.

The dynamic radial load is the calculated constant radial load, which a group of identical bearings with stationary outer rings can theoretically endure for a rating life of 1 million revolutions of the inner ring.

4 Bolt Composite material UCSF204 stainless steel units and Zirconia Ceramic bearing

Seals and Shields

Seals and shields provide protection from contamination and as a retainer for lubricant.  Seals provide better protection and lubricant containment than shields, but have lower maximum speed capabilities. Seals and shielding options for ceramic bearings include:

• None or open bearing
• Single seal
• Double seal
• Single shield
• Double shield

Bearing Design

One directional angular contact bearings tolerate some misalignment. Same radial load as deep-groove bearings, but 2-3 times the thrust load.

Double direction angular contact thrust ball bearings are double row bearings constructed with uniquely designed inner and outer rings.

Double row angular contact ball bearings have two rows of balls in a single inner and outer ring. These bearings are similar to double row angular contact bearings, except that they are of the maximum capacity (filling slot) variety. The higher number of balls results in much higher load carrying capacity.

Duplex thrust angular contact bearings are two match-ground one-directional thrust bearings used as a set.

In Conrad or deep groove bearings the balls rotate in a deep groove machined into the inner and outer races.

A double row deep groove bearing is a modified version of the single row deep groove ball bearing through the addition of a second raw of balls.

Maximum capacity bearings have a higher load capacity than the Conrad type but diminished thrust capacity. 

Maximum capacity double row bearings are a modified version of the maximum capacity single row ball bearing through the addition of a second raw of balls.

Four point contact bearings are single row angular contact bearings designed such that the ball has four contact points, two with the outer race and two with the inner race.

Features

Common features for ceramic bearings include:

• Thin-section
• Self-aligning
• Flanged
• Stainless steel construction
• Prelubricated
• Relubricatable
• Solid lubrication

Standards

Ceramic bearing quality is rated by ABEC (Annular Bearing Engineers' Committee). These ratings classify different accuracy and tolerance ranges for bearings. The higher the ABEC number the tighter the bearing tolerances. ANSI -American National Standards Institute and AFBMA - Anti-friction Bearing Manufacturers Association specifies other standards.

ISO 3290-2 - This part of ISO 3290 specifies requirements for finished silicon nitride balls for rolling bearings.

ISO 14627 - This International Standard describes a test method that covers the determination of fracture resistance of silicon nitride bearing balls at room temperature by the indentation fracture (IF) method.