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 Ra ≤ 0,2 μm or Rz ≤ 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 1).
Suitable materials for the raceways include steels for through-hardening, such as 100Cr6 in accordance with ISO 683-17:1999, 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 P0/C0 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. 1). Threaded holes in the housing shoulders also enable the use of bolts to push the bearing from its seat (fig. 2).
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. 3 and fig. 4). Recommended dimensions for the appropriate grooves, ducts and threaded holes to connect the oil supply are listed in table 1 and table 2.