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. 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.