Support surfaces

To maximize service life of ball bearing units, the support surfaces must be manufactured to:
  • a roughness of Ra ≤ 12,5 μm
  • a flatness (planicity) tolerance to IT7

When a heavy load, parallel to the housing base, acts on a ball bearing unit (fig. 1), SKF recommends doweling the housing to the support surface. The position and size of the holes for the dowel pins are listed in the relevant product tables.

Ball bearing flanged units

Depending on the design flanged housings may have a centring recess (fig. 2), or a centring shoulder (fig. 3) at the back for accurate positioning, either on an appropriate shoulder or in a bore in the machine wall. Housings in the series FY .. M, FYJ, FYTB .. M, FYTJ, FYK and FYTBK have a centring recess while FYC housings do have a centring shoulder. For dimensions and tolerances, refer to the relevant product tables.

An appropriate shoulder can be provided by one of the following methods:

  • machining the wall accordingly (fig. 4)
  • attaching an appropriate washer to the wall by several screws (fig. 5)

Furthermore, these features relieve the attachment bolts of radial forces.

SKF logo