Basic Size

ISO 286 fit calculations are implemented from independently published open data rather than a Machinery’s Handbook transcription. The supported release scope is 3–400 mm. Numerical cells are re-provenanced against Parker Greene’s isofits project (MIT licence) and independently cross-checked by ShopMath against a second ISO 286 implementation.

Zones s, t and u are intentionally excluded because the open cross-check dataset identifies those zones as not adequately supported by its independent-source method. Formulae are used only to combine validated IT grades and fundamental deviations; missing table cells are not generated from approximate equations.

Fit type is determined from the worst-case hole-minus-shaft range: always positive = clearance fit, always negative = interference fit, and a range that crosses zero = transition fit. ISO standards remain the authoritative engineering specification.