Ball and roller bearings

Bearing selection

Each type of bearing has characteristic features which make it particularly suitable for certain applications. However, it is not possible to lay down hard and fast rules for the selection of bearing types since several factors must be considered and assessed relative to each other. The following recommendations will, for a given application, serve to indicate those details of greatest importance in deciding the type of bearing to be used.

Available space

In many instances at least one of the main dimensions of the bearing, usually the bore, is predetermined by

ELLIPTICAL

Mainly for grease-facilitates initial distribution of lubricant.

FIGURE OF EIGHT

Mainly for grease. Recommended where lubrication is infrequent.

ELLIPTICAL

Mainly for grease-facilitates initial distribution of lubricant.

Fig. 28.2 Types of groove which can be added for lubrication

Mainly for grease. Recommended where lubrication is infrequent.

ANNULAR

For pressure oil feed. Distributes oil circumferentially and axially.

AXIAL

Mainly for gravity oil feed. Groove must be remote from loaded area.

ANNULAR

For pressure oil feed. Distributes oil circumferentially and axially.

Mainly for gravity oil feed. Groove must be remote from loaded area.

HELICAL-LEFT OR RIGHT HAND

HELICAL-LEFT OR RIGHT HAND

For grease or oil. Used to distribute and convey lubricant axially.

Fig. 28.3 Prelubricated bearings have an acetal co-polymer lining. The indentations in the linings provide a series of grease reservoirs

Fig. 28.4 Fully machined components from self lubricating materials produced by powder metallurgy

Fig. 28.3 Prelubricated bearings have an acetal co-polymer lining. The indentations in the linings provide a series of grease reservoirs

Fig. 28.4 Fully machined components from self lubricating materials produced by powder metallurgy

Pressed Powder Bearings
Fig. 28.5 Components pressed to finished size by powder metallurgy techniques
Pressed Powder Bearings
Fig. 28.6 Dry bearings requiring no lubrication with a PTFE /lead bearing surface
Fig. 28.7 Standard wrapped bushes, steel backed lined with lead bronze

Fig. 28.8 Thick walled bearings are produced as bushes, half bearings and thrust washers in copper and aluminium base alloys, also tin and lead base white metals

Plain Thrust Bearing
Fig. 28.9 Structural plain bearings

Fig. 28.8 Thick walled bearings are produced as bushes, half bearings and thrust washers in copper and aluminium base alloys, also tin and lead base white metals the machine design. Deep groove ball bearings are normally selected for small diameter shafts whereas cylindrical roller bearings, spherical roller bearings and deep groove ball bearings can be considered for shafts of large diameter.

If radial space is limited then bearings with small sectional height must be selected, e.g. needle roller assemblies, certain series of deep groove bearings and spherical roller bearings.

Where axial space is limited and particularly narrow bearings are required then some series of deep groove ball bearings and cylindrical roller bearings can be used.

Bearing loads

Magnitude of load - This is normally the most important factor in determining the size of bearing. Generally, roller bearings can carry greater loads than ball bearings of the same external dimensions. Ball bearings are mostly used to carry light and medium loads, whilst roller bearings are often the only choice for heavy loads and large diameter shafts.

Direction of load - Cylindrical roller bearings having one ring without flanges and needle roller bearings can only carry radial loads. Other types of radial bearing can carry both radial and axial loads.

Thrust ball bearings are only suitable for axial loads. Spherical roller thrust bearings, in addition to very heavy axial loads, can also carry a certain amount of simultaneously acting radial load.

A combined load comprises a radial and an axial load acting simultaneously.

The most important feature affecting the ability of a bearing to carry an axial load is its angle of contact. The greater this angle the more suitable is the bearing for axial loading. Refer to maker's catalogue for individual values. Double and single row angular contact ball bearings are mainly used for combined loads.

Self aligning ball bearings and cylindrical roller bearings can also be used to a limited extent. Duplex bearings and spherical roller thrust bearings should only be considered where axial loads predominate.

Where the axial component constitutes a large proportion of the combined load, a separate thrust bearing can be provided for carrying the axial component independently of the radial load. In addition to thrust bearings, suitable radial bearings may also be used to carry axial loads only.

Angular misalignment

Where a shaft can be misaligned relative to the housing, bearings capable of accommodating such misalignment are required, namely self aligning ball bearings, spherical roller bearings, spherical roller thrust bearings or spherical plain bearings. Misalignments can, for example, be caused by shaft deflection under load, when the bearings are fitted in housings positioned on separate bases and large distances from one another or, when it is impossible to machine the housing seatings at one setting.

Limiting speeds

The speed of rotation of a rolling bearing is limited by the permissible operating temperature. Bearings with low frictional resistance and correspondingly little internal heat generation are most suitable for high rotational speeds. For radial loads, the highest bearing speeds are obtainable with deep groove ball bearings or cylindrical roller bearings and for combined loads the highest bearing speeds are obtainable with angular contact ball bearings.

Precision

Rolling bearings with a high degree of precision are required for shafts where stringent demands are made on running accuracy, e.g. machine tool spindles and usually for shafts rotating at very high speeds.

Deep groove ball bearings, single row angular contact ball bearings, double row cylindrical roller bearings and angular contact thrust ball bearings are manufactured to high degrees of precision both as regards running accuracy and dimensions. When using high precision rolling bearings, shaft and housings must be machined with corresponding accuracy and be of rigid construction.

Rigidity

Elastic deformation in a loaded rolling bearing is very small and in most instances can be ignored. However the bearing rigidity is of importance in some cases, e.g. for machine tool spindles.

Due to the greater area of contact between the rolling elements and raceways, roller bearings, e.g. cylindrical roller bearings or taper roller bearings, deflect less under load than ball bearings. The rigidity of the bearings can be increased by suitable preloading.

Axial displacement

The normal bearing arrangement consists of a locating (fixed) bearing and a non locating (free) bearing. The non locating bearing can be displaced axially thus preventing cross location, e.g. by shaft expansion or contraction. Cylindrical roller bearings having one ring without flanges or needle roller bearings are particularly suitable for use as free bearings. Their internal design permits axial displacement of the inner and outer rings in both directions. The inner and outer rings can therefore be mounted with interference fits.

Light and medium radial loads

Heavy radial loads

Loads in restricted radial space

Axial loads

i ►

m

m

Radial and axial combined loads, a is the angle of contact

Radial and axial combined loads, a is the angle of contact mL

Angular misalignment

Rigidity

Misalignment Ball Flanges

ADC Limiting speeds

Radial and lighter axial combined loads

n-

-U

DDE Axial displacement

A C D D

Precision

Ease of mounting with cylindrical bore

CH3'

Adapter sleeve added

Ease of mounting with taper bore

Fig. 28.10 (continued)

Withdrawal sleeve added

Deep groove ball bearings (Fig. 28.11)

Deep groove ball bearings are available in both single row and double row designs. Single row ball bearings are the most popular of all rolling bearings. They are a simple design, non separable, suitable for high speed operation and require little attention in service. The deep grooves enable axial loads to be carried in either direction. Bearings are available with shields and seals and can be supplied with the correct quantity of lithium base grease and used in operating temperatures between -30° and +110°C. Special bearings operate over a wider range. Relubrication in service is not required. Shielded and sealed bearings are primarily intended for applications where the inner ring rotates. In cases where the outer ring rotates, there is a risk that lubricant will be lost and the manufacturer should be consulted.

Snap rings, fitted to bearings with snap ring grooves provide a simple means of location.

Deep groove ball bearings have very limited ability to accommodate errors of alignment.

Fig. 28.11 Single and double row deep groove ball bearings

Mounting and dismounting

The rings of separable bearings (cylindrical roller bearings, needle roller bearings, taper roller bearings) are fitted separately. Thus, when an interference fit is required for both inner and outer rings or where there is a requirement for frequent mounting and dismounting, they are easier to install than non separable bearings (deep groove ball bearings, angular contact ball bearings, self aligning ball bearings and spherical roller bearings).

It is easy to mount or dismount bearings with taper bores on tapered seatings or when using adapter withdrawal sleeves on cylindrical shaft seatings. Figure 28.10 gives a simplified guide showing the suitability of the more popular types of bearing for particular applications. The type of bearing indicated for each of the features should be considered as a first choice, but not necessarily the only choice. The bearings listed are described later.

A - Deep groove ball bearing,

B - Self aligning ball bearing,

C - Angular contact ball bearing,

D - Cylindrical roller bearing,

E - Needle roller bearing,

F - Spherical roller bearings,

G - Taper roller bearing,

H - Thrust ball bearing,

J - Spherical roller thrust bearing,

K - Spherical plain bearing,

L - Double row angular contact thrust bearing.

Fig. 28.11 Single and double row deep groove ball bearings

Self-aligning ball bearings (Fig. 28.12)

Self-aligning ball bearings have two rows of balls and a common sphered raceway in the outer ring and this feature gives the bearing its self aligning property which permits a minor angular displacement of the shaft relative to the housing. These bearings are particularly suitable for applications where misalignment can arise from errors in mounting or shaft deflection. A variety of designs are available with cylindrical and taper bores, with seals and adapter sleeves and extended inner rings.

Fig. 28.12 Self aligning ball bearings with cylindrical bore

Angular contact ball bearings (Fig. 28.13)

In angular contact ball bearings the line of action of the load, at the contacts between balls and raceways, forms an angle with the bearings axis. The inner and

Fig. 28.13 Single and double row angular contact ball bearings

outer rings are offset to each other and the bearings are particularly suitable for carrying combined radial and axial loads. The single row bearing is of non-separable design, suitable for high speeds and carries an axial load in one direction only. A bearing is usually arranged so that it can be adjusted against a second bearing.

A double row angular contact bearing has similar characteristics to two single bearings arranged back to back. Its width is less than two single bearings and can carry an axial load in either direction. These bearings are used for very accurate applications such as the shafts in process pumps.

Cylindrical roller bearings (Fig. 28.14)

In cylindrical roller bearings the rollers are guided between integral flanges on one of the bearing rings. The flanged ring and rollers are held together by the cage to form an assembly which can be removed from the other ring. This separable feature of the bearing design facilitates mounting and dismounting, particularly where, because of loading conditions, interference fits for both rings are necessary. Single and double row bearings are available for heavy loads, high speeds and rigidity. Typical applications are for machine tools and heavy electric motors.

Needle roller bearings (Fig. 28.15)

The chief characteristic of needle roller bearings is that they incorporate cylindrical rollers with a small diameter/length ratio. Because of their low sectional height these bearings are particularly suitable for applications where radial space is limited. Needle roller bearings have a high load carrying capacity in relation to their sectional height.

Fig. 28.15 Needle roller bearings

(a) With inner ring, (b) needle roller cage assembly, (c) drawn cup needle roller bearings with open ends, (d) drawn cup needle roller bearings with closed end

Fig. 28.15 Needle roller bearings

(a) With inner ring, (b) needle roller cage assembly, (c) drawn cup needle roller bearings with open ends, (d) drawn cup needle roller bearings with closed end

Spherical roller bearings (Fig. 28.16)

Spherical roller bearings have two rows of rollers which run on a common sphered raceway in the outer ring, the inner ring raceways each being inclined at an angle to the bearing axis. The bearings are self aligning and permit minor angular displacements of the shaft relative to the housing which may occur in mounting or because of shaft deflection under load. Heavy duty types are avialable for severe operating conditions encountered in vibrating machinery such as soil compactors.

Engineering Drawing Balls

Fig. 28.14 Single and double row cylindrical roller bearings

Fig. 28.16 Spherical roller bearing

Taper roller bearings (Fig. 28.17)

In a taper roller bearing the line of action of the resultant load through the rollers forms an angle with the bearing axis. Taper roller bearings are therefore particularly suitable for carrying combined radial and axial loads.

Fig. 28.14 Single and double row cylindrical roller bearings

Fig. 28.17

The bearings are of separable design, i.e. the outer ring (cup) and the inner ring with cage and roller assembly (cone) may be mounted separately.

Single row taper roller bearings can carry axial loads in one direction only. A radial load imposed on the bearing gives rise to an induced axial load which must be counteracted and the bearing is therefore generally adjusted against a second bearing.

Two and four row taper roller bearings are also made for applications such as rolling mills.

Thrust ball bearings (Fig. 28.18)

Thrust ball bearings are designed to accommodate axial loads. They are not suitable for radial loads. To prevent sliding at the ball to raceway contacts, caused by centrifugal forces and gyratory moments, thrust ball bearings must be subjected to a certain minimum axial load. The bearings are of separable design and the housing and shaft washers may be mounted independently.

Ball Thrust Bearings Drawing Free Sketch
Fig. 28.18 Single row thrust ball bearing

Spherical roller thrust bearings (Fig. 28.19)

In spherical roller thrust bearings the line of action of the load at the contacts between the raceways and the rollers forms an angle with the bearing axis, and this makes them suitable for carrying a radial load. This radial load must not exceed 55% of the simultaneous acting axial load. The sphered raceway of the housing washer provides a self aligning feature which permits, within certain limits, angular displacement of the shaft relative to the housing.

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Responses

  • ANTONINO
    What is preloading of bearing Draw one typical bearing mounting showing preloading arrangement?
    8 years ago
  • Renuka
    Here you explained briefly about all major types of ball bearings with structural diagrams. Multi rowed ball bearings increases capacity and heavy-duty in applications.<br />
    7 years ago
  • Hannu
    How to draw sectional drawing of ball bearing?
    3 years ago
  • pandora clayhanger
    How many types of bearing drawing in iti?
    3 years ago
  • Ari-Pekka
    How to draw a ball bearing showing all components?
    2 years ago
  • Sofia Petros
    How to draw roller bearings?
    2 years ago
  • cosimo
    How to draw a ball bearing using sketch approach?
    2 years ago
  • niklas
    How to draw taper bearing?
    2 years ago
  • henri
    How to draw a ball and roller bearingengineering drawing?
    7 months ago

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