A rotating Ø30 mm shaft carries a normal, stationary load. What fit belongs to the shaft, and what fit belongs to the housing?
Load relative to the ring
Assess the load direction relative to each bearing ring. A load rotating around a ring generally requires interference to prevent creep; a stationary ring load may permit a looser fit. Knowing that the shaft or housing rotates is insufficient: the force direction may rotate too.
Factors in shaft fit selection
Load magnitude is one selection criterion alongside bearing type, diameter, accuracy, material, temperature and ring loading. A normal load alone does not determine a final fit for the Ø30 mm shaft. Use the manufacturer table for the specific bearing and loading case; the tool gives only a preliminary indication.
Fixed and floating side in the housing
A locating bearing positions the shaft axially; a non-locating bearing permits thermal length changes. This does not automatically determine the housing fit. Axial movement can occur inside the bearing or between a ring and its seat. H7 is therefore not a universal non-locating bearing fit; check ring loading, arrangement and manufacturer guidance.
Assumptions and applicability limits
This guideline holds up to Ø50 mm, for deep-groove ball bearings with a cylindrical bore and the common loading case. A hollow shaft, significant heat generation or a co-rotating outer ring call for a different fit than given here. For critical or deviating applications, consult the bearing manufacturer's full selection table.