Page 184 - Rollingbearings

Bearing execution

B 7 Bearing execution

Selecting internal clearance

Selecting internal
As part of the bearing selection process, As a general rule:
when the bearing type, size, and it have
been determined, additional factors must be clearance or • Ball bearings should have an operating
considered to enable you to further deine clearance that is virtually zero
the inal variant of the bearing preload • Cylindrical, needle, spherical and CARB
In this section you can ind recommenda- toroidal roller bearings typically require at
tions and requirements for selecting: least a small operational clearance
Bearing internal clearance (ig. 1) is deined • Tapered roller and angular contact ball
• the bearing internal clearance or preload as the total distance through which one bearings should have a small operational
• the bearing tolerances bearing ring can be moved relative to the clearance, except in applications where a
• the appropriate cage (where applicable) other in the radial direction (radial internal high degree of stiffness or positional con-
• integral seals (where applicable) clearance) or in the axial direction (axial trol is required, in which case they can be
• additional options, such as coatings and internal clearance) mounted with a degree of preload
other features to meet any special needs/ Initial internal clearance is the internal
requirements clearance in the bearing prior to mounting Sections Selecting initial internal clearance
Bearing execution ance in the bearing after mounting but prior ing factors that you must consider and pro-
and Selecting preload, describe the inluenc-
Mounted clearance is the internal clear-
vide the methods by which you can calculate
to operation
Operating clearance is the internal clear-
the initial internal clearance needed to
achieve the degree of operational clearance/
ance in the bearing when it is in operation
preload required by your application
and has reached a stable temperature
In most applications, the initial internal
B.7 clearance in a bearing is greater than its
operating clearance This is because of the
effects of (ig. 2):

• interference its with the shaft and/or Fig. 1
housing Bearing internal clearance
• thermal expansion of the bearing rings
and associated components
Radial internal clearance
Bearings must have the appropriate operat-
ing clearance to operate satisfactorily
(Importance of selecting correct clearance/
preload)
In most cases, bearings require a certain
degree of clearance (Selecting initial internal
clearance) However, in some cases, they
may require preload (i e negative clearance,
refer to Selecting preload, page 186)

Axial internal clearance

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