Calculation & verification notes

Scope and method

This application calculates dimensional limits for cylindrical shafts and bores. It uses numeric upper/lower deviations from the tabulated classes in ISO 286-2:2010, with the 2013 numerical corrigendum applied. It does not approximate fundamental deviations with general-purpose formulas.

For each component: minimum size = basic dimension + lower deviation; maximum size = basic dimension + upper deviation. Tolerance width = upper deviation − lower deviation. Each lookup uses a range open at its lower endpoint and closed at its upper endpoint. For example, exactly 50 mm uses the range above 30 through 50 mm; 50.001 mm uses the next applicable range. Some fundamental deviations have finer ranges than the IT-width table.

Minimum clearance = minimum bore − maximum shaft. Maximum clearance = maximum bore − minimum shaft. Classification follows the size-limit relationship in ISO 286-1:2010 clauses 3.3.3.1–3.3.3.3. A zero endpoint is permitted in clearance or interference fits. A range spanning negative and positive values is transition. The app reports signed clearance rather than positive interference magnitude.

Each dimension is parsed as an exact decimal, with up to 12 decimal places. Internal integer arithmetic uses 10⁻¹³ mm increments. Conversion uses exactly 25.4 mm per inch. Calculated limits and classifications use unrounded values; metric displays normally use three decimal places and retain extra digits for fractional-micron values; inch display values are rounded and marked ≈. Changing units retains the exact stored dimensions until you edit a dimension. Three decimal places in millimetres represents 1 µm, not 10 µm. Increase imperial display precision when inspecting very small inch values.

Unequal basic dimensions are a useful custom limit comparison. They are not a conventional ISO shared-basic-size fit designation. Both ranges are looked up independently. Nominal dimensions and permissible sizes must be positive.

Supported ranges and exclusions

407 tabulated tolerance classes, with 7,282 class/range records. Overall nominal range: greater than 0 to 3150 mm, limited by the availability of each class. IT1–IT18 are offered where tabulated. IT01, IT0 and untabulated combinations are not implemented. Positions A/a and B/b, and grades IT14–IT18, are not accepted at or below 1 mm. Other smaller ranges follow the actual source tables.

The za11 entry above 225 to 250 mm is excluded: the consulted table’s endpoints do not agree with its IT11 width. The application does not invent a replacement. Blank source entries are unavailable, even when an extension could potentially be calculated under ISO 286-1.

The 2013 numerical corrections cover A9, H1, JS1, J6, S9, S10, c12, k13 and x9. Symmetric JS/js values are interpreted as equal positive and negative deviations, including entries with omitted ± typography. The S9 correction at above 100 to 120 mm is interpreted with a negative sign, consistent with the upper deviation and the IT9 width.

Verification and limitations

Automated tests validate every shipped row’s tolerance width against the standard IT table, ordered/non-overlapping intervals, and inclusive range boundaries. Additional tests cover independent dimensions, all three fit classifications, exact zero clearance, unit conversion, single-component modes, malformed inputs, exclusions, corrigendum cases and backup validation.

Reference comparisons use separate manufacturer tables: SKF publication 06116/1 EN, page 74, Tables 3 and 4, and Schaeffler HG1 shaft-deviation values. These independently check representative common shaft and housing classes; they are not a second-source audit of every one of the 7,282 records.

The dimensional reference temperature is 20 °C. The app does not predict assembly force, contact pressure, torque capacity, temperature behaviour, elastic or plastic deformation, surface roughness or geometrical form. Selecting a preset does not establish that a fit is suitable for a particular application.

Cloud browser testing covers input changes, live results and local saved calculations. A narrow-width preview checks responsive layout. Native iPhone installation, offline relaunch and AirPrint require a final check on the HTTPS-hosted app.

Fit Finder

Fit Finder enumerates supported opposing classes and user-constrained diameters, then calls the same calculator engine for every candidate. It searches at most 101 diameters and 25,000 class/diameter combinations. Targets constrain the whole interval, not merely a nominal midpoint. Zero-at-limit cases are identified separately from guaranteed positive clearance or guaranteed interference.

Common-pair priority is a documented display preference based on a curated subset of MISUMI’s fit selection tables (JIS B 0401-1 excerpt). It applies only to equal basic dimensions. No material, load, stress or assembly-force suitability is inferred. All numeric deviations still come from the unchanged ISO 286 data.

Three proposals can be compared with the known component on one diameter axis. Use This Fit transfers ordinary calculator inputs, preserving the existing favourite and backup format.

References

• ISO 286-1:2010 — Basis of tolerances, deviations and fits
• ISO 286-2:2010 — Tables of standard tolerance classes and limit deviations
• ISO 286-2:2010/Cor 1:2013 — Corrections
• SKF — Spherical plain bearings and rod ends, publication 06116/1 EN
• Schaeffler — Plain bearings, HG1

Source documents are not redistributed. The application contains numeric engineering data and original interface/engine code, not copies of the standard’s text, page layouts or the reference calculator’s code.