Can a shaft fit specified for a solid shaft be copied unchanged to a hollow shaft?

LILY Bearing | 2026-10-28

Best answer

Include the support stiffness behind the fitted surface

An interference fit deforms the bearing ring and the mating part.

The amount of deformation and contact pressure depend on more than the nominal outside diameter. JTEKT lists shaft and housing thickness and material among fit-selection considerations, which is directly relevant when changing to a hollow shaft. A tolerance selected for a solid section should therefore not be copied merely because the bearing bore is unchanged. The revised design also needs to consider shaft strength, support and operating loads. This is a reason to obtain the appropriate calculation, not a claim that hollow shafts are inherently unsuitable for bearing seats.

Show the wall thickness explicitly in the comparison

For an illustrative 50 mm outside diameter, a 40 mm bore leaves a 5 mm wall, while a 10 mm bore leaves a 20 mm wall.

These simple geometric results do not calculate fit pressure, but they expose a difference hidden by the phrase “same 50 mm shaft.” Put the inside diameter, material, seat length and relevant loads on the review drawing. Ask the responsible engineer to check the fit method for that geometry, including ring deformation and remaining clearance where applicable. Retain the calculation basis with the changed shaft drawing so the original solid-shaft assumption cannot silently survive the redesign.