TorqueMath

ISO Fits and Tolerances Calculator

Pick a fit like H7/g6 and a size to get the limits of the hole and shaft, the clearance or interference, and how hot to heat the hub for a shrink fit. Values to ISO 286 for sizes up to 500 mm.

TorqueMath.com · ISO Fits and Tolerances Calculator
mm
Fit (hole basis, ISO preferred)
Or choose any hole and shaft
°C
e-6/K
Steel 11.5, cast iron 10.5, stainless 16, bronze 18, aluminium 23 µm/m·K.
Tolerance zones around the nominal line

All preferred fits at this size

FitUseHoleShaftClearance (+) / interference (−)Type

How it is calculated

Each tolerance is a fundamental deviation (the letter, which sets the position) plus a standard tolerance grade IT (the number, which sets the width), both from ISO 286-1 tables for the size range.

Shaft a…h es = fundamental deviation (≤ 0), ei = es − IT Shaft j…zc ei = fundamental deviation (≥ 0), es = ei + IT Hole A…H EI = −es of the same shaft letter, ES = EI + IT Hole K, M, N ES = −ei + Δ (grades ≤ 8), Δ = IT(n) − IT(n−1) Hole P…ZC ES = −ei + Δ (grades ≤ 7) JS / js ± IT / 2 Max clearance = ES − ei Min clearance = EI − es (negative = interference) Shrink-fit heat ΔT = (max interference + 0.001·D) / (α · D)

The extra 0.001 × D in the shrink-fit formula is the minimum clearance needed to slide the hot hub on before it cools. Keep steel below about 250 °C to avoid changing its hardness, and use the shaft-cooling method (dry ice −78 °C, liquid nitrogen −196 °C) when heating alone is not enough.

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