Press-fit tolerance calculator (probabilistic interference)
Deterministic (worst-case) and probabilistic interference for a press fit from the bore and shaft tolerance bands, using an inverse-normal-CDF approximation for the chosen reliability interval.
Std. deviation, bore, σ_hub3.5 µm
Std. deviation, shaft, σ_shaft2.17 µm
Mean interference, m24 µm
Combined std. deviation, s4.12 µm
Interference, worst-case minimum7 µm
Interference, worst-case maximum41 µm
Interference, probabilistic minimum14.42 µm
Interference, probabilistic maximum33.58 µm
The deterministic Min/Max is the worst-case (fully stacked) tolerance approach; the probabilistic Min/Max is the more realistic approach assuming normally distributed tolerances. The interference should still be corrected for surface roughness.
Method & references
- Press-fit tolerance analysis per DIN ISO 286: 1990.
- Probability interval 0.98 means 98% of the area under the normal distribution, i.e. 1% left over on each side.
The computation is a literal port of the original client-side JavaScript from /calculators/c1_3.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.