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Ball bearing units consists of pre-lubricated sealed ball bearings and a housing which varies in shape. They are capable of aligning themselves efficiently using the spherical fitting surface between the bearing and housing, effectively preventing overloads due to misalignment.
Deep groove ball bearings are available in a variety of sizes, and are the most popular of all rolling bearings. This type of bearing supports radial load and a certain degree of axial load in both directions simultaneously.
Cylindrical roller bearings have high radial-load capacity and moderate thrust loads. They contain rollers which are cylindrically-shaped, but are not true cylinders. Instead, these rollers are crowned or end-relieved to reduce stress concentrations. This geometry results in low friction and allows for high-speed applications. Cylindrical roller bearings are commonly available in precision grades such as RBEC-5, a classification from the Roller Bearing Engineers Committee (RBEC). RBEC ratings describe the accuracy and tolerance range for different types of bearings. As a rule, the higher the RBEC number, the tighter the bearing tolerances. Typically, cylindrical roller bearings are lubricated with oil, which also serves as a coolant.
Tapered roller bearings are designed such that cup, cone and rollers have tapered surfaces whose apexes converge at a common point on the bearing axis. Along with metric series bearings, inch series bearings are also available. This type of bearing is suitable for applications that involve heavy or impact loading.
Needle roller bearings are small in sectional height, therefore useful in making machinery smaller and lighter. This type of bearing is used in a wide range of machinery, such as automobiles, motor cycles, electric machines, machine tools, aerospace and office equipment.
Angular contact bearings are designed such that a contact angle between the races and the balls is formed when the bearing is in use. The major design characteristic of this type of bearing is that one, or both of the ring races have one shoulder relieved, or higher than the other. In order for these bearings to function properly, they must be assembled with a thrust load. This loading (or preload) creates a line of contact (or contact angle) between the inner race, the ball and the outer race. The preload can be built into the bearing or created when the bearing is inserted into an assembly. The contact angle varies from 15° to 40° and is measured relative to a line running perpendicular to the bearing axis. Angular contact bearings are unidirectional thrust bearings that can withstand heavy thrust loads and moderate radial loads.
Spherical roller bearings feature a large load rating and self-aligning capability. This type of bearing is suitable for low or medium speed applications which involve heavy or impact loading.
Thrust ball bearings are divided into single and double direction types. The former is able to accommodate axial load in one direction, while the latter is able to accommodate it in both directions. Neither is suitable for applications that involve radial load or high-speed rotation.
The Codex line of EXSEV (Extreme Special Environment) bearings were specifically engineered for the tough applications such as those involving high temperatures, corrosive solutions and atmospheres, dry lubrication, low particle emissions, non-magnetic environments and high vacuum conditions. Codex meets the challenge with specialty steels, silicon nitride bearing components and advanced dry film coatings for protection and low particle emissions.
A bearing is any one of various machine elements that constrain the relative motion between two or more parts to only the desired kind of movement. This is usually to allow and promote free rotation around a fixed axis or free linear movement; it may also be to arrest any motion, such as by controlling the vectors of normal forces. Bearings may be classified according to the motions they allow and according to their principle of operation, as well as by the directions of applied loads they are able to handle.
The first documented use of a bearing was in an axle assembly by the carriage maker and inventor Mr Phillip Vaughan in 1791. Mr Vaughan utilized ball bearings to do away with the direct contact between the drive shaft and axle in the carriages he manufactured which put an end to carriage axles wearing out as a result of the friction they were subjected to.
A very early type of linear bearing was some tree trunks laid down under wooden sleds. This technology may date as far back as the construction of the Pyramids in Egypt, though there has never been any definitive evidence to prove this theory. Modern linear bearings use a similar principle, they just use balls in place of rollers most of the time.
A bearing is considered to be a thin section bearing when the bore diameter is greater than four times the radial cross section. Within any thin section ball bearing series, the cross section remains constant as the bore diameter changes. Typically the cross section is twice the ball diameter, and nominal dimensions are given in imperial measurements.
We take so many things in life for granted! As usual I woke up this morning and turned on my bedside lamp that is mounted on a revolving base, I got out of bed and opened my bedroom door, ran a bath, went downstairs to make a cup of coffee and drove to work. Sounds like any other day, but I got to thinking about how many of my activities were made easier or even possible because of the ball bearing and where we would be in a world without this revolutionary invention.