Thrust bearings are designed for pure thrust loads, and can handle little or no radial load. The rolling element in a thrust bearing can be a ball, needle or roller. Design units can be specified in English units of inches, metric units or both. Important dimensions to consider when searching for thrust bearings include the bore, the outside diameter and the overall 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 it is a housed unit, but exclude the flange if a flanged bearing.
Important operating specifications to consider when searching for thrust bearings include rated speed, static axial or thrust load, and dynamic axial or thrust load. The rated speed for a bearing running with grease lubrication is lower than a bearing with oil lubrication. The static axial or thrust load is the maximum axial load bearing can endure without excessive permanent deformation. 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.
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.
Bearing Design Choices
Bearing design choices for thrust bearings include flat race thrust ball, grooved race thrust ball, two directional grooved thrust, needle roller thrust, cylindrical roller thrust, spherical roller thrust, and slewing ring or turntable bearing. Flat-race thrust bearings consist of a ball retainer held between two flat washers. Grooved race thrust bearings consist of a ball retainer held between two grooved washers. Two directional grooved thrust bearings are 'back-to-back' grooved race thrust bearings. Needle roller thrust bearings consist of a needle roller and cage assembly. Cylindrical roller thrust bearings consist of a roller and cage assembly. Spherical roller thrust bearings have a spherical raceway in the outer ring. Slewing ring or turntable bearings can accommodate axial, radial and moment loads.
Special Material Considerations
Special material considerations that are available for thrust bearings include stainless steel, plastic, ceramic, and plated. Stainless steel is chemical and corrosion resistant and can have relatively high-pressure ratings. Plastics include any of numerous organic, synthetic, or processed materials that are mostly thermoplastic or thermosetting polymers of high molecular weight. A ceramic hybrid bearing is constructed of steel inner and outer rings with ceramic (typically Si3N4) balls in place of steel. 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 operating life. Bearings containing all ceramic balls are also nonconductive and are commonly used in electric motor applications. Common plating materials are cadmium and chrome.
Related Products & Services
Aerospace bearings are designed to meet the rigorous demands of aircraft control and aerospace applications.
Ball bearings are used to provide smooth, low friction motion in rotary applications. Ball bearings types include radial ball bearings (deep groove and angular contact) and thrust ball bearings.
Insert bearings and wide inner ring bearings mount to shafts via setscrews or locking collars.
Miniature Bearings and Instrument Bearings
Miniature bearings and instrument bearings carry moderate radial and thrust loads at low operating torque while providing high performance in a small envelope design. These types of bearings are single row ball bearings available in up to 1 1/8" outer diameter (OD) sizes
Needle Roller Bearings
Needle roller bearings are a type of radial roller bearing with rollers whose length are at least four times their diameter. These bearings are valued for their high load capacity and low sectional height.
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.
Thin-section bearings have small cross-sections with respect to their diameter.