H8/k7 fit — Transition fit

ISO 286 hole-basis transition fit. Enter a nominal size to get the limits.

Nominal size

Unit

Result

Ø25.000 H8/k7Transition fit

	Upper	Lower	Max	Min	Tol.
Hole H8	+0.033	0	25.033	25.000	0.033
Shaft k7	+0.023	+0.002	25.023	25.002	0.021

Max clearance: 0.031 mm
Max interference: 0.023 mm
Mean: +0.004 mm

Fit diagram (µm · zero line = nominal)

Hole tolerance zoneShaft tolerance zoneClearanceInterference

About H8/k7

Coarser transition for general machinery where H7/k6 is unnecessarily accurate.

At Ø25 mm the hole H8 measures 0 mm to +0.033 mm and the shaft k7 +0.002 mm to +0.023 mm, giving between 0.023 mm interference and 0.031 mm clearance.

How the limits are calculated

Hole H8: fundamental deviation EI = 0, standard tolerance IT8 = 33 µm for 18–30 mm. Shaft k7: fundamental deviation ei = 2 µm, IT7 = 21 µm. Clearance = hole − shaft, evaluated at both extremes. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.

H8/k7 limits by size range

Size (mm)	Hole H8	Shaft k7	Clearance min	Clearance max
≤ 3	+0.014 / 0	+0.010 / 0	−0.010	+0.014
3 – 6	+0.018 / 0	+0.013 / +0.001	−0.013	+0.017
6 – 10	+0.022 / 0	+0.016 / +0.001	−0.016	+0.021
10 – 18	+0.027 / 0	+0.019 / +0.001	−0.019	+0.026
18 – 30	+0.033 / 0	+0.023 / +0.002	−0.023	+0.031
30 – 50	+0.039 / 0	+0.027 / +0.002	−0.027	+0.037
50 – 80	+0.046 / 0	+0.032 / +0.002	−0.032	+0.044
80 – 120	+0.054 / 0	+0.038 / +0.003	−0.038	+0.051
120 – 180	+0.063 / 0	+0.043 / +0.003	−0.043	+0.060
180 – 250	+0.072 / 0	+0.050 / +0.004	−0.050	+0.068
250 – 315	+0.081 / 0	+0.056 / +0.004	−0.056	+0.077
315 – 400	+0.089 / 0	+0.061 / +0.004	−0.061	+0.085
400 – 500	+0.097 / 0	+0.068 / +0.005	−0.068	+0.092

Deviations in mm at the upper end of each range; negative clearance = interference. Clearance columns are shown on wider screens. Sub-ranges (e.g. 18–24 / 24–30) can differ for r, s, t, u, v, x, y, z — use the calculator for the exact size. “—” means ISO 286 doesn't define this class below that size (e.g. t only starts at 24 mm).

Is H8/k7 a clearance fit?

Not always — H8/k7 is a transition fit per ISO 286 (see types of fits). At Ø25 mm it gives between 0.023 mm mm interference and 0.031 mm mm clearance, depending which parts of the tolerance zones are paired.

What is the H8/k7 tolerance at 25 mm?

At a nominal size of Ø25 mm, H8 allows a hole diameter from 25.000 to 25.033 mm, and k7 allows a shaft diameter from 25.002 to 25.023 mm.