Ceramic bearings are rotary bearings constructed of ceramic. 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. 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, and extended operation life. Bearings containing all ceramic balls are also nonconductive and are commonly used in electric motor applications.
Important dimensions to consider when specifying ceramic bearings include bore, outside diameter, and outer ring width. 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.
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. Seals and shielding options for ceramic bearings include none or open bearing, single seal, double seal, single shield, or double shield. 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.
Bearing design choices applicable for ceramic bearings include one direction angular contact, double direction angular contact, double row angular contact, maximum capacity double row angular contact, duplex thrust angular contact, Conrad or deep groove, double row deep groove, maximum capacity, maximum capacity double row, and four point contact. 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.
Common features for ceramic bearings include thin-section, self-aligning, flanged, stainless steel construction, ceramic races and plating. Lubrication options include prelubricated, relubricatable, and solid lubrication.
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Super Precision and Spindle Bearings
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