Wherever you have movement you create friction. Sometimes that friction is necessary to create grip but at other times friction is unwanted, creating noise, wearing components and increasing drag. A bearing is a way of minimising friction and unwanted movement.
One look at a bearing supply company such as Bearing Boys will offer a dazzling array of bearings for almost every situation and budget. So much so that you might be left scratching your head in puzzlement at which type of bearing you need.
Usually when we talk about bearings we mean a rolling-element bearing where the load is carried on balls or rollers to reduce friction. These balls or rollers can be held between two channels or races in the outer casing so that they move freely but only in the desired direction. Lubricant, in the form of grease or oil, is used to further minimise friction.
Ball Bearing
Small metal balls are captured between the inner and outer races of the unit and allowed to roll freely around the circumference. The balls can be made of chrome steel or stainless steel.
Deep Groove Ball Bearing
A type of low maintenance ball bearing supplied as a single unit. Both radial and axial loads can be tolerated. They can be supplied with rubber or metal seals or a combination depending on the application requirements.
Roller Bearing
A roller bearing uses rollers to perform the same function as the balls in a ball bearing. The rollers are guided using internal flanges on at least one of the rings. Different flange designs allow the bearing to permit or deny axial displacement of the shaft.
Tapered Bearing
A type of roller bearing where the inner and outer raceways and the rollers themselves are shaped as a section of a cone where the point of the cone would be along the shaft. This allows them to deal with combined axial and radial loads and cope with misalignment of the shaft. They can be used singly, in pairs where the two bearings taper in opposite directions and in four-row designs of two pairs.
Needle Bearing
A needle bearing is a type of roller bearing that uses many small rollers. This provides a large contact area between the bearing and load which allows the bearing to carry heavier loads, even at high speeds. Caged designs have a retainer to maintain needle spacing and for guidance.
Linear Bearing
A very simple form of bearing consisting of a simple polythene collar that surrounds the shaft. This allows them to be self-lubricating resulting in a low maintenance system.
Ball Transfer Units
These consist of a large ball held captive in a metal housing so that it can rotate freely. They can be used to minimise friction when moving loads in any direction. They can be spring mounted and are usually used in groups.
Choosing Your bearings
If you are replacing a bearing, the quickest and easiest way to ensure that you have the correct type is simply to look at the reference code (for example 63142ZR.C3) on the outer casing and ask your chosen bearing supplier.
It’s not always quite so simple though, and sometimes you have to measure your bearing. There are three vital statistics: inner diameter, outer diameter and width. These can be used to determine the bearing type number, 6314 in the example above.
Bearings also have seals between the inner and outer raceways. The next section of the reference code indicates the type of seals, rubber, metal or a combination. The final section of the code indicates the clearance value- the amount of space allowed for heat expansion and movement between the rings.
Now that you’ve more of an idea of where bearings can be used, you should be able to order the right one for the job.
