MechaPoint — Engineering Solutions
Limits & Fits Calculator
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Limits & Fits Calculator & Assembly Advisor

Select the standard, the nominal size and the fit. The tool returns the limit deviations to the ISO 286 code system and to ASME B4.1 and B4.2, and writes the result as ready drawing callouts, including the symmetric form. For interference fits it checks contact pressure and yield safety and prepares a heating and cooling plan. If you only know the clearance or interference you need, the reverse tab finds the nearest standard fits. All calculations run locally in your browser.
  1. 1
    Choose standard, size and fit
    ISO 286 (all classes), ASME B4.2 preferred metric fits, or ASME B4.1 inch classes RC·LC·LT·LN·FN.
  2. 2
    Read limits, callouts and the fit range
    Tolerance-zone diagram, max/min material limits, copyable asymmetric and symmetric callouts.
  3. 3
    Check assembly & disassembly
    Contact pressure, yield safety, press-out force and a heat/cool plan grounded in shop practice.

1Standard & nominal size

ISO 286-1/-2 code system: any hole class (A…ZC + grade) against any shaft class (a…zc + grade), 0–500 mm. Sizes 500–3150 mm are available in the full version.

2Fit selection

Preferred fits. The dot shows the fit type at the current size:
Hole class
/
Shaft class

3Interference & assembly inputs

Used by the press/shrink-fit check and the thermal plan (shown when the fit can produce interference).
Custom material entry (own E, ν, Re, α) is part of the full version.

4Export & share

Ø25 H7/g6 CLEARANCE FIT
Min clearance
—
tightest condition
Max clearance
—
loosest condition
Fit tolerance
—
total variation of the fit
Tolerance zone diagramHole and shaft tolerance zones relative to the zero line
Hole tolerance zone Shaft tolerance zone zero line = nominal size · vertical axis in display units

Drawing callouts

The same fit written three ways: with the fit symbol, with explicit limit deviations, and as a symmetric ± tolerance on an adjusted nominal. Click copy to paste into a drawing note or CAD.

Press and shrink fit check

Method: Lamé thick-wall elasticity, von Mises check at the hub bore and shaft (see Budynas–Nisbett, Shigley’s Mechanical Engineering Design, press & shrink fits); embedding loss and guideline friction per DIN 7190.

Thermal assembly plan

What do H7/g6, H7/p6 … mean?

The letter positions the tolerance zone relative to the nominal size (the fundamental deviation); the number is the IT grade (its width). Capital letters are holes, lowercase are shafts. H7/g6 is a close sliding clearance fit; H7/k6 a transition fit; H7/p6 a light interference fit; H7/s6 and H7/u6 are drive/force fits.

Hole basis or shaft basis?

Hole basis (H hole, fit set by the shaft) is preferred in practice because holes are made with fixed tooling (drills, reamers). Shaft basis (h shaft) is used when a common shaft (e.g., drawn bar, linear shafting) carries several parts with different fits.

Is ASME B4.2 the same as ISO 286?

ASME B4.2 adopts the ISO 286 system (same IT grades and fundamental deviations) and defines a preferred subset of ten hole-basis and ten shaft-basis fits with preferred sizes. ASME B4.1 is the older inch system with its own RC/LC/LT/LN/FN classes.

How hot may I heat the hub for a shrink fit?

Practice limits (per DIN 7190 guidance): structural steels and cast iron ≈ 350 °C, quenched & tempered steels ≈ 300 °C, surface-hardened ≈ 250 °C, case-hardened ≈ 200 °C, rolling bearings ≈ 120 °C (sealed: 80 °C), age-hardened aluminium considerably lower. Cooling media: freezer −40 °C, dry ice −78 °C, liquid nitrogen −196 °C. This tool plans heating, cooling, or a combination accordingly.

MechaPoint — Engineering Solutions

The free version covers the everyday cases. Extended features such as the PDF fit report, batch tables, sizes above 500 mm and custom material input are in preparation and can be requested by e-mail. Questions, corrections and suggestions are always welcome.

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Values are computed algorithmically per the methodology of the ISO 286 code system (ISO 286-1) and the ANSI/ASME B4.1 fit-class definitions; tables from the standards are not reproduced. “ISO 286”, “ASME B4.1” and “ASME B4.2” are referenced solely to identify the applicable methodology; this tool is not affiliated with, endorsed by, or certified by ISO or ASME. For design release, always verify against the official standards (available from iso.org and asme.org). Press/shrink-fit mechanics use classical Lamé thick-wall elasticity with a von Mises yield check (cf. Budynas–Nisbett, Shigley’s Mechanical Engineering Design); embedding loss, guideline friction coefficients, joining temperatures and the 0.001·D assembly clearance follow DIN 7190 practice. Material properties are typical reference values; always confirm with your material certificate. The tool is intended for capability demonstration; it may contain errors, gaps and, in some cases, software bugs, and must not be relied upon alone for design, manufacturing or acceptance decisions. For customized solutions and verified engineering, MechaPoint.