Sleeve Bearings

Sleeve bearings have no rolling elements so each surface slides relative to one another. This sliding action creates more heat than rolling element bearings thus RPM is often a limiting factor. The applications that generally use these bearings have a slow speed/motion spectrum with moderate loads. The loads are generally limited to hundreds of pounds depending upon size with speeds generally less than 500 RPM. The critical information necessary for selecting a sleeve bearing is the load and velocity of the mating components. Life of sleeve bearings is dictated largely by the environment and maintenance care. Due to the sliding action between the two surfaces these bearings tend to wear over time. Some plain bearings are pressurized with lubrication separating the two surfaces during operation.

Boston Gear offers the following list of materials in different configurations such as bushings, bushings with flanges and washers. Lengths of solid bars and cored bars are also available. 

Rolling Element Bearings

Bearings with rolling elements are often called antifriction bearings because they have lower friction, generate less heat, and mechanical losses are lower. These bearings could have balls or some type of roller as the rolling element. The rolling elements are ground to precise tolerances and need to be protected (sealed), lubricated adequately and handled carefully. These bearings require a small gap between the rolling element and the raceways. This gap is the bearing clearance and is necessary for thermal expansion of the metal components. Rolling element bearings do not wear like plain bearings and therefore the bearing clearance stays constant throughout the life of the bearing.

These bearings can be designed to carry radial loads, thrust loads, and combinations of both. Selecting the right bearing for the load/application is critical for bearing performance. For a sealed and greased bearing the critical selection criteria revolves around the applied load, and the RPM. With this information bearing life can be reliably predicted.

Ball Bearings

Ball bearings can run at very high speeds but generally cannot carry very high loads. They must be well aligned or allowed to align within a spherical housing. The spherical housing is typical for mounted type ball bearings (i.e. pillow blocks, flanges…). Standard deep groove ball bearings do not carry heavy thrust loads but angular contact ball bearings can carry moderate thrust loads. The raceways are generally honed to provide smooth quiet operation in many household appliances such as electric motors, fans, and pumps. These bearings can be supplied with or without grease and seals. The clearance in this bearing is controlled by the combination of balls and raceway diameters.

Boston Gear offers the following ball bearings in many different configurations.

• 1600, 7500, 400F & 3000 series single row ball bearings sealed and unsealed
• 7600 series extended inner race single row ball bearings, set screw mounted
• 6900 series flanged mounted single row ball bearings, set screw mounted
• AO, SAO, 600 series thrust ball bearings banded and unbanded
• 2000, 2100, 2000 series sheaves and wheels ball bearing mounted
• Mounted ball bearings in pillow blocks, flanges, piloted flanges in cast iron, cast steel
• Pressed steel options with set screws or eccentric locking collars

Tapered Roller Bearings

These are the workhorse bearings for many industrial applications. The roller in this bearing is tapered similar to a cone with the point cut off. This bearing must be well aligned due to the rigid length of the roller. Excessive misalignment will cause edge loading of the roller and quick failures. This bearing does not run at very high speeds but is designed for high load applications. It will carry both heavy radial and combination thrust loads. Common applications are automotive wheel bearings, speed reducers and industrial equipment. This bearing is generally supplied as a non sealed separable two piece bearing. The bearing clearance must be adjusted during the assembly process.

Spherical Roller Bearings

Spherical roller bearings have rollers that are typically shaped like an old wooden barrel. These bearings are also a workhorse for many industrial applications. This bearing is designed to accept misalignment from heavy loads or mounting inaccuracy unlike the tapered roller bearing. Spherical bearings will run at moderate speeds with heavy radial and combination loads. The most common applications are large paper mills, steel processing plants, and industrial equipment. This bearing is commonly found sealed and lubricated in mounted bearing products (pillow blocks, flange blocks…) but the unsealed version is also common in industrial applications like the tapered roller bearing. The naked bearing has the bearing clearance built into the raceway size.

Cylindrical/Needle Roller Bearings

The rollers in these bearings are shaped like a cylinder. The needle bearing has a roller that is much smaller and longer than a cylindrical bearing. The cylindrical bearing can run at high speeds and high loads but can not handle significant thrust loads like the tapered roller bearing. Cylindrical bearings are most commonly found unsealed and are used in industrial applications. The clearance is built into this bearing by controlling the size of the rollers and the raceways.