Page 49 - SKF-bearing-housings

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Design considerations

Specifications for shafts and housing
support surfaces
Shaft

Bearing seat
Recommended fits for bearings on solid steel
shafts in cast iron housings are provided in the
SKF catalogue Rolling bearings and are avail-
able online at skf.com/bearings.
If adapter or withdrawal sleeves are used, the
sleeve seat on the shaft should be machined to
tolerance class h9V E or better. The total radial
runnout should be IT5/2 for tolerance class
h9V E .
If bearings are to be mounted directly onto
the shaft, the cylindricity tolerance and total
runout tolerance of the bearing seat should,
depending on the requirements, be one to two
IT tolerance grades better than the prescribed
dimensional tolerance. Abutments for bearing
rings should have a perpendicularity tolerance
and total axial runout tolerance that is at least
one IT tolerance grade better than the diameter
tolerance of the associated cylindrical seat.
Seal seat or counterface
Recommendations are provided in the relevant
product chapter. Generally, seal counterfaces
should be machined to tolerance class h9V E or
better and the cylindricity should be to toler-
ance grade IT5.
Surface roughness
At the sleeve and seal positions, the shaft
surface should have a surface roughness
R a ≤ 3,2 µm (125 µin.). Recommendations for
the surface roughness of cylindrical bearing
seats are provided in the SKF catalogue Rolling
bearings and are available online at
skf.com/bearings.
Housing support surface
To maximize bearing service life and prevent
deformation of the housing bore, SKF recom-
mends that the flatness of the housing support
surface is to tolerance grade IT7 in accordance
with ISO 1101. The surface should be finished
to a surface roughness R a ≤ 12,5 µm (500 µin.).

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