1. Type and Features of Rolling Contact Bearings
1.1 Classification and Types of Rolling Contact BearingsIn general, rolling contact bearings may be classified as radial or thrust bearings according to bearing design or they may be classified as ball or roller bearing according to the type for rolling element.
Radial bearings are mainly designed for supporting a load perpendicular to a shaft axis
Whereas thrust bearings accept loads parallel to the shaft axis..
Using the ball or roller classification roller bearings may be further divided according to the shape of the roller into the sub-classes; cylindrical roller, Tapered roller, Spherical roller, or Needle roller bearings. Ball bearings can be further divided according to the number of rows into either single-row or double row (for thrust ball bearings, single direction and double direction) Ball bearings may be still further sub-divided into small segments according to the relationship between the bearing rings and rolling elements; the shape of bearings rings; and use of accessories.
Bearings are also classified by specific application, such as wheel bearings for automotive application.
1.2 Rolling Contact Bearings Designs and FeaturesRolling contact bearings usually consist of an inner ring, outer ring, and rolling elements (ball or rollers), and a cage which positions the rolling elements at fixed intervals between the ring raceway.
Standard materials for inner and outer rings, and for the rolling elements, are high carbon chromium bearings steel or case hardening steel. The steel is heat-treated to an appropriate hardness to attain optimum resistance to rolling fatigue. Bearings surfaces are ground to a very high accuracy using special machine tools.
While each of the carious types of rolling contact bearings has special features, the following features are common to most rolling contact bearings type.
Rolling contact bearings have relatively low starting resistance. There is little difference between the starting and running resistance of rolling contact bearings.
Dimensions and accuracy are standardized ready-made products of high quality are easy to obtain.
Compared to ‘’sliding’’ bearings, rolling contact bearings are less prone to wear and help to maintain the accuracy of the machine in which they are used.
Rolling contact bearings consume small amounts of lubricant and far less costly to maintain than sliding-type bearings.
To get optimum performance from a selected bearing, it is necessary to understand the design and features of the various bearings types and to then select bearings optimal to individual machine performance.
1.2.1 Deep Grove Ball BearingsDeep grove ball bearings are the most popular of all the ball bearings types because they are available in a wide variety of seals, shield and snap-ring arrangements.
The bearings ring grooves are circular arcs made slightly larger than the radius of the ball. The balls make point contact with the raceways (elliptical contact when loaded). The inner ring shoulders are of equal height (as the outer ring shoulders).
Deep groove ball bearings can sustain radial, axial, or composite loads and because of simple design, this bearings type can be produced to provide both high-running accuracy and high-speed operation.
Deep groove ball bearings having an outside diameter less then 9mm are known as miniature ball bearings. Deep groove ball bearings having an outside diameter > 9mm and a bore diameter < 10 mm are known as extra-small ball bearings.
Standard ball retainers (cages) are made from pressed steel. Machined cages are used in press steel. Machined cages are used in bearings operating at very high speeds or for large diameter bearings.
Deep groove ball bearings with seals or shields are standardized. They contain paper amount of grease in advance.
1.2.2 Single-row Angular Contact Ball BearingThe raceways of both the inner and outer rings of this bearing type are made with a set contact angle. These bearings are non-separable since the balls are inserted utilizing counter-bore construction, a larger number of balls can be installed than in the case of deep groove ball bearings.
Standard café materials may be pressed steel, high-strength brass, or synthetic resin. Cage material is dependent on the bearing series and or service condition.
Single-row angular contact ball bearings can sustain radial, axial or composite loads. However, any axial load must be in one direction.
This bearing type is generally used in pairs to handle the induced load resulting from the internal axial force generated by the applied radial load. When mounting tow single bearings in adjacent position, all bearings manufacturing brands are provides these combination parts (pairs) with readjusted clearance. Paired combination bearings are matched sets. Combination or paired bearings can be arranged BACK-TOBACK, FACE-TO-FACE, or TANDEM sets can sustain bidirectional axial loads.
1.2.3 Double-row Angular Contact Ball Bearings.The construction of this ball bearing type is similar to the adjacent, BACK-TO-BACK mounting of two single-row angular contact ball bearings. Because fewer balls can be inserted per row compared to single-row angular contact ball bearings, a double-row angular contact ball bearing will have less load capacity then an equivalent size/series BACK-TO-BACK set of two single-row angular contact ball bearings.
The type bearings can sustain radial, moment and bi-direction axial loads.
1.2.4 Self-aligning Ball BearingsThis type is constructed with the inner ring and ball assembly contained within an outer ring which has a spherical raceway. Due to the construction, this bearing type will tolerate a small angular misalignment from deflection or mounting error. Self-aligning ball bearing suitable for long shafts where accurate positioning of housing bore is difficult. This type is often used in conjunction with pillow blocks. Cages are made from pressed steel or polyamide resin.
This bearing should only be used in light axial load application due to the small axial support of the elements by outer ring raceway.
1.2.5 Cylindrical Roller Bearings.Constriction of this roller bearing type is the simplest of all radial roller bearings.
This bearing type is often used in high-speed applications. Because the inner rings, outer rings, rollers are in line contact; this bearings type has a large radial load capacity. Various cylindrical
roller bearing configurations:
N,NJ,NF,NU,RNU: integral ribs (flanges)
NH, NP, NUP, NUH: integral and loose ribs
NN, NNU: double-row bearings
Configuration having integral flags or loose ribs on both the inner and outer rings can sustain a small amount of axial load. Since this bearings type supports axial loads as sliding action between the end of the rollers and flange faces, axial loading limited
Double-row cylindrical roller bearings are used for high-speed, high-accuracy applications such as; main spindle support for lathes, milling machines, and machining centers. Radial clearance of tapered-bore bearings can be adjusted during mounting of the bearing(s) onto the mating shaft.
Standard cages are pressed steel or polyamide resin. Machined cage of high-strength brass are used for bearings of large dimension or for high-speed application.
1.1 Classification and Types of Rolling Contact BearingsIn general, rolling contact bearings may be classified as radial or thrust bearings according to bearing design or they may be classified as ball or roller bearing according to the type for rolling element.
Radial bearings are mainly designed for supporting a load perpendicular to a shaft axis
Whereas thrust bearings accept loads parallel to the shaft axis..
Using the ball or roller classification roller bearings may be further divided according to the shape of the roller into the sub-classes; cylindrical roller, Tapered roller, Spherical roller, or Needle roller bearings. Ball bearings can be further divided according to the number of rows into either single-row or double row (for thrust ball bearings, single direction and double direction) Ball bearings may be still further sub-divided into small segments according to the relationship between the bearing rings and rolling elements; the shape of bearings rings; and use of accessories.
Bearings are also classified by specific application, such as wheel bearings for automotive application.
1.2 Rolling Contact Bearings Designs and FeaturesRolling contact bearings usually consist of an inner ring, outer ring, and rolling elements (ball or rollers), and a cage which positions the rolling elements at fixed intervals between the ring raceway.
Standard materials for inner and outer rings, and for the rolling elements, are high carbon chromium bearings steel or case hardening steel. The steel is heat-treated to an appropriate hardness to attain optimum resistance to rolling fatigue. Bearings surfaces are ground to a very high accuracy using special machine tools.
While each of the carious types of rolling contact bearings has special features, the following features are common to most rolling contact bearings type.
Rolling contact bearings have relatively low starting resistance. There is little difference between the starting and running resistance of rolling contact bearings.
Dimensions and accuracy are standardized ready-made products of high quality are easy to obtain.
Compared to ‘’sliding’’ bearings, rolling contact bearings are less prone to wear and help to maintain the accuracy of the machine in which they are used.
Rolling contact bearings consume small amounts of lubricant and far less costly to maintain than sliding-type bearings.
To get optimum performance from a selected bearing, it is necessary to understand the design and features of the various bearings types and to then select bearings optimal to individual machine performance.
1.2.1 Deep Grove Ball BearingsDeep grove ball bearings are the most popular of all the ball bearings types because they are available in a wide variety of seals, shield and snap-ring arrangements.
The bearings ring grooves are circular arcs made slightly larger than the radius of the ball. The balls make point contact with the raceways (elliptical contact when loaded). The inner ring shoulders are of equal height (as the outer ring shoulders).
Deep groove ball bearings can sustain radial, axial, or composite loads and because of simple design, this bearings type can be produced to provide both high-running accuracy and high-speed operation.
Deep groove ball bearings having an outside diameter less then 9mm are known as miniature ball bearings. Deep groove ball bearings having an outside diameter > 9mm and a bore diameter < 10 mm are known as extra-small ball bearings.
Standard ball retainers (cages) are made from pressed steel. Machined cages are used in press steel. Machined cages are used in bearings operating at very high speeds or for large diameter bearings.
Deep groove ball bearings with seals or shields are standardized. They contain paper amount of grease in advance.
1.2.2 Single-row Angular Contact Ball BearingThe raceways of both the inner and outer rings of this bearing type are made with a set contact angle. These bearings are non-separable since the balls are inserted utilizing counter-bore construction, a larger number of balls can be installed than in the case of deep groove ball bearings.
Standard café materials may be pressed steel, high-strength brass, or synthetic resin. Cage material is dependent on the bearing series and or service condition.
Single-row angular contact ball bearings can sustain radial, axial or composite loads. However, any axial load must be in one direction.
This bearing type is generally used in pairs to handle the induced load resulting from the internal axial force generated by the applied radial load. When mounting tow single bearings in adjacent position, all bearings manufacturing brands are provides these combination parts (pairs) with readjusted clearance. Paired combination bearings are matched sets. Combination or paired bearings can be arranged BACK-TOBACK, FACE-TO-FACE, or TANDEM sets can sustain bidirectional axial loads.
1.2.3 Double-row Angular Contact Ball Bearings.The construction of this ball bearing type is similar to the adjacent, BACK-TO-BACK mounting of two single-row angular contact ball bearings. Because fewer balls can be inserted per row compared to single-row angular contact ball bearings, a double-row angular contact ball bearing will have less load capacity then an equivalent size/series BACK-TO-BACK set of two single-row angular contact ball bearings.
The type bearings can sustain radial, moment and bi-direction axial loads.
1.2.4 Self-aligning Ball BearingsThis type is constructed with the inner ring and ball assembly contained within an outer ring which has a spherical raceway. Due to the construction, this bearing type will tolerate a small angular misalignment from deflection or mounting error. Self-aligning ball bearing suitable for long shafts where accurate positioning of housing bore is difficult. This type is often used in conjunction with pillow blocks. Cages are made from pressed steel or polyamide resin.
This bearing should only be used in light axial load application due to the small axial support of the elements by outer ring raceway.
1.2.5 Cylindrical Roller Bearings.Constriction of this roller bearing type is the simplest of all radial roller bearings.
This bearing type is often used in high-speed applications. Because the inner rings, outer rings, rollers are in line contact; this bearings type has a large radial load capacity. Various cylindrical
roller bearing configurations:
N,NJ,NF,NU,RNU: integral ribs (flanges)
NH, NP, NUP, NUH: integral and loose ribs
NN, NNU: double-row bearings
Configuration having integral flags or loose ribs on both the inner and outer rings can sustain a small amount of axial load. Since this bearings type supports axial loads as sliding action between the end of the rollers and flange faces, axial loading limited
Double-row cylindrical roller bearings are used for high-speed, high-accuracy applications such as; main spindle support for lathes, milling machines, and machining centers. Radial clearance of tapered-bore bearings can be adjusted during mounting of the bearing(s) onto the mating shaft.
Standard cages are pressed steel or polyamide resin. Machined cage of high-strength brass are used for bearings of large dimension or for high-speed application.