SKF - Rolling Bearings

Radial location of bearings
Bearings with a tapered bore
Bearings with a tapered bore can be mounted
directly on tapered shaft seats, or on adapter
or withdrawal sleeves († figs. 25 to 28, page
207). Sleeves that are fitted to cylindrical
shaft seats have an external taper. Whether
the bearing is mounted on a sleeve or directly
on the shaft, the fit of the bearing inner ring is
not pre-determined by the bearing seat, as is
the case for bearings with a cylindrical bore.
Instead, the fit for bearings with a tapered
bore is determined by the distance through
which the ring is driven up on its tapered seat
or on the sleeve. Special precautions relative
to the internal clearance reduction must be
considered as mentioned under Bearing clearance
(† page 213) and under Self-aligning ball
bearings († page 537), Spherical roller bearings
(† page 879), and CARB toroidal roller bearings
(† page 957).
If the bearings are to be mounted on an
adapter or withdrawal sleeve, larger diameter
tolerances are permitted for the sleeve seat,
but the tolerances for total radial run-out
must be tighter († Dimensional and geo metric
al tolerances of bearing seats and abutments,
page 200).
Recommended fits
The tolerances for the bore and outside diameter
of rolling bearings are standardized internationally
(† Tolerances, page 132).
To achieve an interference or loose fit for
metric bearings with a cylindrical bore and
outside surface, suitable tolerance classes for
the bearing seat on the shaft and in the housing
bore are selected from the ISO tolerance
system. Only a limited number of ISO tolerance
classes need be considered for the shaft
and housing seats for rolling bearings. The location
of the most commonly used tolerance
classes relative to the bearing bore and outside
diameter surface are shown in fig. 17,
page 170 (valid for bearings with Normal
tolerances).
Each ISO tolerance class is identified by a
letter and a number. The letter, lower case for
shaft diameters and upper case for housing
bores, locates the tolerance zone relative to
the nominal dimension. The number indicates
the range of the tolerance zone. The higher the
number, the larger the tolerance zone.
Recommendations for bearing fits for solid
steel shafts are provided in the tables referenced
in the following:
• radial bearings with a cylindrical bore
(† table 2, page 172)
• thrust bearings († table 3, page 174)
Recommendations for bearing fits for cast iron
and steel housings are provided in the tables
referenced in the following:
• radial bearings – non-split housings
(† table 4, page 174)
• radial bearings – split or non-split housings
(† table 5, page 175)
• thrust bearings (†table 6, page 175)
These recommendations are based on the
general selection guidelines described above,
which take developments in bearing and housing
materials, design and manufacturing into
account. Modern bearings and housings can
accommodate substantially heavier loads than
was previously possible. The recommendations
in this catalogue reflect these improvements.
NOTE: All ISO tolerance classes are valid with
the envelope requirement (such as H7VE ) in
accordance with ISO 14405-1. For practical
reasons, this is not indicated in the following
tables.
ISO 14405-1 offers more possibilities to
specify fits. For additional information, contact
the SKF application engineering service.
169
F