A Guide to Bearings

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A guide to bearings

Bearing glossary| Bearing FAQ's| Search bearing data| Life calc's| Bearing selection|Tolernce systems| Bearing materials table| Bearing retainer materials| Bearing

seal/shield materials| Bearing fitting Bearing part number systems

Stop and consider how many things in your life turn or revolve. skatewheels, electric motors, car wheels, microwave turntables, even yourPC has bearings in it.

The humble bearing makes many of today's machines a reality.Without them we would not be able to make precision items on amassive scale and things would wear out quickly due to excessivefriction. This page is designed to give you an idea of what bearings

are, what they do and the formats they come in.

Simply put...

All things roll and rotate better than they slide. If the wheel did notexist we would be stuck with sliding things everywhere.Consequently little progress in the world would be achieved. Slidingcauses friction. Friction is caused by two surfaces resistingmovement between them. If however two surfaces can contact eachother by rolling then friction problems are significantly reduced.

Bearings reduce friction either by using hard smooth balls or rollers,

and a smooth inner and outer surface for the balls to roll against orby introducing a low friction surface between the surfaces. Theseballs or rollers "bear" any loads which they may be subjected to thusallowing the bearing to rotate smoothly.

How bearings 'bear' load

Ball bearings are typically capable of dealing with two kinds ofloading condition; radial load and thrust load. Depending on the typeof application the bearing is used in, it may experience radial loadonly, thrust load only or a combination of both. A classic examplebeing the car wheel as shown below.

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Different Bearing types

There are many types of bearings, each used for different purposeseither singularly or in combinations. These include ball bearings,roller bearings, ball thrust bearings, roller thrust bearings andtapered roller thrust bearings.

Ball bearings

Ball bearings, as shown to the left, are themost common type by far. They are foundin everything from skate boards towashing machines to PC hard drives.These bearings are capable of taking bothradial and thrust loads, and are usuallyfound in applications where the load islight to medium and is constant in nature(ie not shock loading). The bearing shownhere has the outer ring cut away revealingthe balls and ball retainer.

Roller bearings

Roller bearingslike the oneshown to theleft are normallyused in heavydutyapplicationssuch asconveyer beltrollers, wherethey must holdheavy radial

loads. In thesebearings theroller is acylinder, so the

contact between the inner and outer race is not a point (like the ballbearing above) but a line. This spreads the load out over a largerarea, allowing the roller bearing to handle much greater loads than aball bearing. However, this type of bearing cannot handle thrustloads to any significant degree. A variation of this bearing design iscalled the needle bearing. The needle roller bearing uses cylindricalrollers like those above but with a very small diameter. This allowsthe bearing to fit into tight places such as gear boxes that rotate athigher speeds.

Thrust ball bearings

Ball thrust bearings like the one shown tothe left are mostly used for low-speed nonprecision applications. They cannot takemuch radial load and are usually found inlazy susan turntables and low precisionfarm equipment.

Roller thrust bearing

Roller thrust bearings likethe one illustrated to theleft can support verylarge thrust loads. Theyare often found ingearsets like cartransmissions betweengear sprockets, and


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between the housing and the rotating shafts. The helical gears usedin most transmissions have angled teeth, this can causes a highthrust load that must be supported by this type of bearing.

Taper roller bearing

Tapered roller bearings are designedto support large radial and large thrustloads. These loads can take the formof constant loads or shock loads.

Tapered roller bearings are used inmany car hubs, where they areusually mounted in pairs facingopposite directions. This gives themthe ability to take thrust loads in bothdirections. The cutaway taper roller onthe left shows the specially designedtapered rollers and demonstrates theirangular mounting which gives theirdual load ability.

Other bearing types..

The above bearing types are some ofthe most common. There are

thousands of other designs, some standard and some specificapplications but all perform the same basic function. Essentiallyfurther types of bearings usually take all or some of thecharacteristics of the above bearings and blend them into onedesign. Through the use of careful material selection and applyingthe correct degree of machining precision, a successful bearingsolution can usually be found.

Bearing glossary| Bearing FAQ's| Search bearing data| Life calc's| Bearing selection| Tolerncesystems| Bearing materials table| Bearing retainer materials| Bearing seal/shield materials| Bearing

fitting


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A Guide to Bearings