IMT 161 Ch 3 AF Bearings

8/13/2019 IMT 161 Ch 3 AF Bearings

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IMT 161Drive Systems

Chapter 3


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Anti-friction bearings

Also called rolling-element or rolling-contact bearings.Serve the same purpose as plainbearings.1. Reduce friction2. Prevent overheating3. Guide & support moving equipment4. Confine motion

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Three general types;1. Journal2. Thrust3. Guide

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All of these have some kind of a rollingelement;1. Balls2. Rollers

Needle bearings are a variation of a rollerbearing.

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Bearing types

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Bearing types

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Cup and Cone

Cage

Roller


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Bearing types

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Ball bearings

In ball bearings the load is carried by arelatively small contact area.Generally, this means;

a lighter load but.at higherspeedsThe more rolling elements in the

bearing, the larger the load that can becarried.

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Anti-friction bearing

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Roller bearings

Roller bearings have a larger contactarea than ball bearings.Generally, this means;

heavier loads at slower speeds

The more rolling elements in thebearing, the larger the load that can becarried.

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Components

Inner ring or race--mounts onto a shaftOuter ring or race--mounts into ahousingRolling elementsCage, retainer or separator--maintainsspacing for the rolling elements andkeeps them securely between the rings.Seals and shields--optional on somebearings.

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Parts

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Parts

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Operating principles

In most applications ;The outer ring is firmly attached to thehousing and does not rotate.

The inner ring is fitted tightly to the shaft,supporting the shaft and confining itsmotion. As the shaft rotates so does theinner ring.The load is carried by the rollingelements.

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Bearing materials

The load carrying parts of most bearingsare made of hardened, ground steel.The rolling elements are case or throughhardened for reliability.How does this compare to plainbearings???

Special bearings can be made ofdifferent grades of steels or alloy steelsfor lighter weight, greater strength,

longer life or for higher temperatures. 16


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Cage materials

Cages, separators or retainers can bemade of many different materials.The most common are;

low carbon steelbrassplastic

nylon

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Cages

Many bearing failures are caused bycage failures.

Most cage failures are caused byinadequate lubrication.

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Seals and shields

Are sometimes called bearing closures.Seals are used to keep lube in andcontaminants out.Bearings with seals on both sides arelubed for life at the factory and can notbe re-lubricated.

Bearings are available with a seal on 1side only.

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Seals and shields

Shields are not as effective as seals inkeeping lube in and contaminants out.Shielded bearings can sometimes be re-lubricated.Shielded bearings might be used with anoil lubrication.

Shields can be used on 1 or both sidesof a bearing.

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Bearing shield

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Bearing Classifications

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Plain Bearings Anti-friction Bearings

Thrust bearings Journal bearings Guide bearings


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Load type

Radial

Axial

Combinations


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Loads

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Radial Load

Radial Load


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Ball

Roller

Needle

Rolling elements

Size

Tolerances


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Standards

Are set by the AFBMA Anti-friction Bearing Manufacturers AssociationBearing Identification Code Standards for ID, OD, width

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Tolerances

To provide precise control of equipmentcomponents, bearings are made andheld to very accurate dimensions.

Vibration control

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Tolerances

Ball bearing tolerances ABEC-1, ABEC-5, ABEC-7, ABEC-9Low numbers mean wider tolerances

Roller bearing tolerancesRBEC-1, RBEC-5Low numbers mean wider tolerances

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Tolerances

Spherical roller bearings are furnished toRBEC-1 tolerances

Tapered roller bearings are designatedby numbers; 00, 0, 2, 3, 4

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Standard & precisionbearings

Standard bearings have about twice thetolerances of precision bearings.

Which type is more expensive?Which do you think might have a longerlife?

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Bearing fits

Operating conditions determine thechoice and type of fit.Manufacturers specifications andbearing charts will provide informationon bearing fits.

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The End!!!!!

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IMT 161 Ch 3 AF Bearings