SKF - Rolling Bearings

Design considerations
Design of associated
components
Raceways on shafts and in housings
If the load carrying capacity of a bearing or assembly
is to be fully exploited, the raceways
machined in associated components for cylindrical
and needle roller bearings with only one
ring, must have a hardness between 58 and
64 HRC. The surface roughness should be
R a ≤ 0,2 μm or R z ≤ 1 μm. For less demanding
applications, lower hardness and rougher surfaces
may be used.
Roundness should be within 25% and the
total radial run-out tolerance should be within
50% of the actual diameter tolerance range of
the raceway.
The permissible axial run-out of the raceways
for thrust assemblies are the same as
for the shaft and housing washers of thrust
bearings († table 10, page 144).
Suitable materials for the raceways include
steels for through-hardening, such as 100Cr6
in accordance with ISO 683-17, steels for
case-hardening, such as 20Cr3 or 17MnCr5 in
accordance with ISO 683-17, as well as steels
for induction-hardening that can be partially
hardened.
The recommended case depth for raceways
machined in associated components depends
on various factors, including the dynamic and
static load ratios (P/C and P 0 /C 0 respectively)
as well as the core hardness, which makes it
difficult to generalize. For example, when core
hardness is 350 HV, the recommended case
depth is generally 0,1 times the rolling element
diameter for purely static loads less than or
equal to the basic static load rating. Shallower
case depths are permitted for dynamic loads.
For additional information, contact the SKF
application engineering service.
Provisions for mounting and
dismounting
Particularly when large bearings are involved,
SKF recommends making provisions during
the design stage to facilitate mounting and
dismounting. If, for example, slots or recesses
are machined in the shaft and/or housing
shoulders, it is possible to apply withdrawal
tools († fig. 31). Threaded holes in the housing
shoulders also enable the use of bolts to
push or pull the bearing from its seat
(† fig. 32).
If the oil injection method is to be used to
mount or dismount bearings on a tapered seat,
or to dismount bearings from a cylindrical
seat, ducts and grooves should be provided in
the shaft († fig. 33). Recommended dimensions
for the appropriate grooves, ducts and
threaded holes to connect the oil supply are
listed in tables 14 and 15.
Fig. 31 Fig. 32
210