Linear bearings are used in machine tools to move the machining tool post or component table in a straight and accurate line. This is done so that the tools like drills, boring bars, taps, etc. can machine the full length that is required. Linear bearings are placed between the housing and the slides. The bearings can be made of various materials such as stainless steel, graphite, bronze, ceramic, plastic, etc.
The main requirements in such applications are high repeatability, durability and low friction. Typically, bearings have precision made rollers, pins or balls that are enclosed in a cage or a frame to rotate around its axis. When the load is placed on it and moved, the rollers or balls rotate and the load is moved forward effortlessly.
There are many types of linear bearings on the market. Some of the most common types are: linear roller, cam follower, ball spline, flat ball cage, hydrostatic, ball bushing, crossed roller, linear motion guide, air, etc. While selecting linear bearings, you need to state the dynamic load capacity and dimensions such as the bearing width, the inside diameter, bearing load capacity and the length, etc. Additional bearing features are: self-lubricating, preloaded, self-aligning, corrosion resistance, and rotary motion etc.
- A linear roller is a set of circulating roller bearings which ride on a round or flat guide.
- A cam follower is a wheel on an axle which runs on bearings.
- A ball spline bearing has balls which contact grooves in a matching spline shaft on at least four sides, depending on the amount of splines.
- A flat ball cage is a non-recirculating or recirculating type of bearing design in which the balls are trapped in a frame that spaces them at equal distance.
- A linear hydrostatic bearing is similar to an air bearing as the body of the bearing rides on a thin film of oil or water for near frictionless movement.
- A ball bushing is like bushing in construction however it has rows of balls to cut down on friction and increase stiffness, accuracy, and smoothness.
- Roller and cross roller bearings are used on linear ways where accuracy and straightness are vital.
- A linear motion guide is a linear profiled rail which has a set of mating bearings that travel along the rail.
- A bearing or rail assembly is a complete assembly that is made up of the bearing and guide or rail.
The housing for linear bearings can be either flanged, none or open, rectangular, and pillow block. The bearing may be open or closed. There are also various features and options for linear bearings such as adjustable preload, clean room use, lubrication port, recirculating bearings, self aligning, vacuum compatible, and wipers or seals.