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Fits & size limits

Read the number: IT tolerance width

An IT grade is a tolerance-width designation. It is not a deviation from nominal and not a guaranteed machining capability.

Sources and scope ↓

What changes with size

A grade must be read at the applicable nominal-size interval. “IT7” without a size does not yield one universal micrometre value.

What the letter adds

In H7, H locates the zone and 7 selects its width. At the documented 25 mm example, H7 has a 21 µm width. The fuller comparison and table sources live on the IT reference page.

Continue your task

Read an IT width and a tolerance-zone position →Read the letter: tolerance-zone position →Calculate clearance from hole and shaft limits →

All tolerance and surface references →

Sources and review scope

Reviewed 23 October 2026. Arithmetic examples are labelled separately from source-table facts and standard scope.

ISO 286-1:2010

Public catalogue: terminology, code system and scope. Full clauses not reviewed.

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KHK hole tolerance table

Manufacturer table explicitly excerpting JIS B 0401-2:1998. H7 row for 25 mm: 0 / +21 µm.

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