H8/n7 fit — Locational transition

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

Nominal size

Unit

Result

Ø25.000 H8/n7Transition fit

	Upper	Lower	Max	Min	Tol.
Hole H8	+0.033	0	25.033	25.000	0.033
Shaft n7	+0.036	+0.015	25.036	25.015	0.021

Max clearance: 0.018 mm
Max interference: 0.036 mm
Mean: −0.009 mm

Fit diagram (µm · zero line = nominal)

Hole tolerance zoneShaft tolerance zoneClearanceInterference

About H8/n7

Firm, near-interference transition fit on an IT8 hole; parts are rarely dismantled once pressed together, e.g. bearing bushes and gear hubs in cost-driven designs.

At Ø25 mm the hole H8 measures 0 mm to +0.033 mm and the shaft n7 +0.015 mm to +0.036 mm, giving between 0.036 mm interference and 0.018 mm clearance.

How the limits are calculated

Hole H8: fundamental deviation EI = 0, standard tolerance IT8 = 33 µm for 18–30 mm. Shaft n7: fundamental deviation ei = 15 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/n7 limits by size range

Size (mm)	Hole H8	Shaft n7	Clearance min	Clearance max
≤ 3	+0.014 / 0	+0.014 / +0.004	−0.014	+0.010
3 – 6	+0.018 / 0	+0.020 / +0.008	−0.020	+0.010
6 – 10	+0.022 / 0	+0.025 / +0.010	−0.025	+0.012
10 – 18	+0.027 / 0	+0.030 / +0.012	−0.030	+0.015
18 – 30	+0.033 / 0	+0.036 / +0.015	−0.036	+0.018
30 – 50	+0.039 / 0	+0.042 / +0.017	−0.042	+0.022
50 – 80	+0.046 / 0	+0.050 / +0.020	−0.050	+0.026
80 – 120	+0.054 / 0	+0.058 / +0.023	−0.058	+0.031
120 – 180	+0.063 / 0	+0.067 / +0.027	−0.067	+0.036
180 – 250	+0.072 / 0	+0.077 / +0.031	−0.077	+0.041
250 – 315	+0.081 / 0	+0.086 / +0.034	−0.086	+0.047
315 – 400	+0.089 / 0	+0.094 / +0.037	−0.094	+0.052
400 – 500	+0.097 / 0	+0.103 / +0.040	−0.103	+0.057

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/n7 a clearance fit?

Not always — H8/n7 is a transition fit per ISO 286 (see types of fits). At Ø25 mm it gives between 0.036 mm mm interference and 0.018 mm mm clearance, depending which parts of the tolerance zones are paired.

What is the H8/n7 tolerance at 25 mm?

At a nominal size of Ø25 mm, H8 allows a hole diameter from 25.000 to 25.033 mm, and n7 allows a shaft diameter from 25.015 to 25.036 mm.