AmesWeb
Limits, Fits, Allowances and Tolerances
This page collects limits, fits, allowances and tolerances resources and tools
based on commonly used standards including ISO 286, ANSI B4.1,
ANSI B4.2 and ISO 2768. The charts and calculators cover both
metric and inch units.
ISO 286-1 and ISO 286-2 – Metric limits and fits
ISO 286 defines the ISO code system of tolerances and fits for linear sizes. It is widely used
to specify hole and shaft tolerances and to select preferred fits in metric systems.
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ISO 286-1 – Basis of tolerances, deviations and fits
ANSI/ASME B4.2 (1978) – Preferred metric limits and fits
ANSI/ASME B4.2 defines preferred metric limits and fits. It is often used as a
reference alongside ISO 286 for metric applications.
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ANSI/ASME B4.2 – Preferred Metric Limits and Fits
ANSI/ASME B4.1 – Preferred limits and fits (inch)
ANSI/ASME B4.1 provides preferred limits and fits for cylindrical parts in inch units,
commonly used in North American practice.
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ANSI/ASME B4.1 – Preferred Limits and Fits for Cylindrical Parts
ISO 2768 – General tolerances
ISO 2768 specifies general tolerances that apply when individual linear or angular tolerances are not
given on the drawing. It is often referenced with a tolerance class (for example ISO 2768-m).
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ISO 2768-1 – Linear and angular dimensions without individual tolerance indications
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ISO 2768-2 – Geometrical tolerances without individual tolerance indications
Interference (press & shrink) fits
For joints that require an interference (press or shrink) fit between shaft and hub,
the following tools provide calculations and supporting formulas.