Including both rolling element bearings and plane bearings, this subset of linear bearings accomplishes the same tasks as its larger counterparts but on a smaller scale. Miniature linear bearings provide repetitive motion that is accurate, smooth, quiet and low friction and are used in dental, medical and industrial industries as well as semiconductors, toys, electronics and watches.
Miniature linear bearings are frequently present in clean rooms or used in medical procedures; shields and seals are available for contamination protection. These bearings are important components of pulmonary assist devices, computer hard drives, fuel controls, motors, cryogenic coolers, flow meters, remote control cars, fishing reels and more. Average miniature linear bearings start from 1 millimeter bore and go up to 10 millimeters, though some companies offer 32 mm miniature bearings; linear bearings in general can reach sizes of more than two meters.
Although the size of miniature linear bearings is much smaller than typical bearings, the kinds, shapes and materials are the same. Available in plastic, stainless steel, chrome steel copper and ceramic, the inner diameter, or bore, can be measured in inches or in millimeters, like metric linear bearings. Because of their smaller size, miniature linear bearings support smaller loads and lower torque though they can still have preloads to help eliminate inner clearance.
Miniature linear bearings are performance tested and can be assembled to exact application requirements. The bearings themselves are typically found inside a steel or aluminum housing that moves with the bearing, called the carriage. There is a stationary base that provides the raceway for the bearing but because of the size constraints, the base and distance traveled is very small, sometimes only a few millimeters long. Miniature linear bearings are generally available in the four main types: linear ball bearings, roller slides, bushings and dovetail slides although there are many variations, such as needle roller bearings or full ball complement bearings.
Miniature linear bearings with rolling elements feature small balls contained within a housing that make contact with another surface to provide low friction motion with high accuracy and tight control, or rigidity. Ball bearings use their spherical elements to travel along a straight line, rolling over a surface. Roller slides contain cylindrical bearings that fit above and below a V shaped groove; the carriage moves along its raceway, which is the groove. Bushings do not use balls for smooth motion but instead have lubricated carriages that move along a shaft. Dovetail slides are similar to roller slides except that the whole slide makes contact with the groove.