refmanualEngineering, within reach.

Fits & size limits

Read the letter: tolerance-zone position

The letter identifies the zone position; the grade number describes its width for the applicable size interval. Uppercase and lowercase distinguish hole and shaft codes.

Sources and scope ↓

H and h example

In the cited examples, H has zero lower deviation and h has zero upper deviation. At 25 mm, H7 extends upward from nominal while h6 extends downward.

Avoid an alphabet shortcut

Do not classify all other letters from a simple alphabet range, or infer a guaranteed fit from a shaft letter alone. Read the size-specific deviations and compare the full mating pair.

Continue your task

Read the number: IT tolerance width →Read an IT width and a 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.

Open the original source ↗
KHK hole tolerance table

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

Open the original source ↗
KHK shaft tolerance table

Manufacturer table excerpting JIS B 0401-2:1998. At 25 mm: h6 −13 / 0 µm; g6 −20 / −7 µm. These are scoped examples, not a full ISO table audit.

Open the original source ↗