N8 tolerance (hole, IT8)

Hole tolerance class N8 per ISO 286-1:2010: fundamental deviation ES −4 … −6, grade IT8 (14 µm at ≤ 3 mm to 97 µm at 400–500 mm). For an exact size, open the calculator with N8 selected.

Type: Hole
Grade: IT8
Tolerance: 14 … 97 µm
Fund. deviation: ES −4 … −6 µm

N8 limits by size range

Size (mm)	Upper (µm)	Lower (µm)	Ø max (mm)	Ø min (mm)	Upper (mm)	Lower (mm)	Dev. (in)
≤ 3	−4	−18	2.996	2.982	−0.004	−0.018	−0.00016 / −0.00071
3 – 6	−2	−20	5.998	5.980	−0.002	−0.020	−0.00008 / −0.00079
6 – 10	−3	−25	9.997	9.975	−0.003	−0.025	−0.00012 / −0.00098
10 – 14	−3	−30	13.997	13.970	−0.003	−0.030	−0.00012 / −0.00118
14 – 18	−3	−30	17.997	17.970	−0.003	−0.030	−0.00012 / −0.00118
18 – 24	−3	−36	23.997	23.964	−0.003	−0.036	−0.00012 / −0.00142
24 – 30	−3	−36	29.997	29.964	−0.003	−0.036	−0.00012 / −0.00142
30 – 40	−3	−42	39.997	39.958	−0.003	−0.042	−0.00012 / −0.00165
40 – 50	−3	−42	49.997	49.958	−0.003	−0.042	−0.00012 / −0.00165
50 – 65	−4	−50	64.996	64.950	−0.004	−0.050	−0.00016 / −0.00197
65 – 80	−4	−50	79.996	79.950	−0.004	−0.050	−0.00016 / −0.00197
80 – 100	−4	−58	99.996	99.942	−0.004	−0.058	−0.00016 / −0.00228
100 – 120	−4	−58	119.996	119.942	−0.004	−0.058	−0.00016 / −0.00228
120 – 140	−4	−67	139.996	139.933	−0.004	−0.067	−0.00016 / −0.00264
140 – 160	−4	−67	159.996	159.933	−0.004	−0.067	−0.00016 / −0.00264
160 – 180	−4	−67	179.996	179.933	−0.004	−0.067	−0.00016 / −0.00264
180 – 200	−5	−77	199.995	199.923	−0.005	−0.077	−0.00020 / −0.00303
200 – 225	−5	−77	224.995	224.923	−0.005	−0.077	−0.00020 / −0.00303
225 – 250	−5	−77	249.995	249.923	−0.005	−0.077	−0.00020 / −0.00303
250 – 280	−5	−86	279.995	279.914	−0.005	−0.086	−0.00020 / −0.00339
280 – 315	−5	−86	314.995	314.914	−0.005	−0.086	−0.00020 / −0.00339
315 – 355	−5	−94	354.995	354.906	−0.005	−0.094	−0.00020 / −0.00370
355 – 400	−5	−94	399.995	399.906	−0.005	−0.094	−0.00020 / −0.00370
400 – 450	−6	−103	449.994	449.897	−0.006	−0.103	−0.00024 / −0.00406
450 – 500	−6	−103	499.994	499.897	−0.006	−0.103	−0.00024 / −0.00406

Deviations at the upper end of each range (Ø columns use that size); use the calculator for the exact size. — : not defined by ISO 286 for that size. Upper/Lower (mm) and inch columns are shown on wider screens.

About N8

N8 denotes a hole tolerance zone with tight transition deviation in the ISO 286 system.

At Ø25 mm N8 is −0.003 / −0.036 mm, i.e. 24.964 to 24.997 mm.

How the limits are calculated

N8 uses grade IT8 (a standard tolerance of 33 µm at 18–30 mm). Fundamental deviation: ES = −ei + Δ (Δ = ITn − IT(n−1), applied up to IT8 for K/M/N and IT7 otherwise); IT8 sets the width below ES. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.

N8 tolerance (hole, IT8)

N8 limits by size range

About N8

How the limits are calculated

Related classes