A guide bearing is a roller, plate or block that reduces wear, maintains alignment and minimizes friction of moving parts. Guide bearings are commonly found on saws, machining tools and other equipment where alignment of moving parts is needed. Smaller bearings may use low-drag polymers or plastics, and larger loads may require the use of metal rollers and lubricants.
Bearings can be exposed to different kinds of loads that affect design requirements. A thrust load is any force that moves the part to one side, such as a car wheel bearing during a turn. Dynamic loads occur when additional load or force is added to the bearing, as can occur when a car hits a bump or dip. Static loads are caused by the weight of the equipment itself, without the addition of other loads.
Band saws are continuous steel saws that rotate around two large drive wheels. A guide bearing is installed on each side of the band saw to permit adjustment of the saw blade. Bearings positioned at the top and bottom of the saw also prevent twisting of the saw band, which is important for keeping the cuts straight.
Roller tables and moving saws may use a V-shaped guide bearing. They can ride along the top or between two V-shaped tracks. The bearing reduces friction, and the V-groove keeps the part in the proper position while allowing movement.
Linear bearings reduce wear for parts that move back and forth in a linear or straight motion. They may be used on machines that perform repetitive motions for assembly or machining operations. The bearing may slide on a track, or the track can pass through the block. A block-style guide bearing may not contain rollers, but may be made from low-friction polymers that resist wear without the need for lubrication.
Larger equipment can use linear bearings, but these may be rollers surrounding the guide shaft. A roller guide bearing can be shaped as a cylinder, with a ring of guide rollers. Placement of these bearings at each end of a moving shaft can provide minimal friction while permitting proper linear motion.
Forklift trucks move equipment and materials by a set of forks attached to a vertical mast. The mast assembly must handle high loads while resisting twisting or bending motions that could damage the mast or the carried equipment. Roller bearings are installed along the mast to minimize thrust and dynamic loads yet allowing free movement of the mast assembly. Low friction is important for masts, because friction will require more power and cause premature wear of hydraulic and mast parts.