N9 tolerance (hole, IT9)
Hole tolerance class N9 per ISO 286-1:2010: fundamental deviation ES −4 … 0, grade IT9 (25 µm at ≤ 3 mm to 155 µm at 400–500 mm). For an exact size, open the calculator with N9 selected.
- Type
- Hole
- Grade
- IT9
- Tolerance
- 25 … 155 µm
- Fund. deviation
- ES −4 … 0 µm
N9 limits by size range
| Size (mm) | Upper (µm) | Lower (µm) | Ø max (mm) | Ø min (mm) | Upper (mm) | Lower (mm) | Dev. (in) |
|---|---|---|---|---|---|---|---|
| ≤ 3 | −4 | −29 | 2.996 | 2.971 | −0.004 | −0.029 | −0.00016 / −0.00114 |
| 3 – 6 | 0 | −30 | 6.000 | 5.970 | 0 | −0.030 | 0 / −0.00118 |
| 6 – 10 | 0 | −36 | 10.000 | 9.964 | 0 | −0.036 | 0 / −0.00142 |
| 10 – 14 | 0 | −43 | 14.000 | 13.957 | 0 | −0.043 | 0 / −0.00169 |
| 14 – 18 | 0 | −43 | 18.000 | 17.957 | 0 | −0.043 | 0 / −0.00169 |
| 18 – 24 | 0 | −52 | 24.000 | 23.948 | 0 | −0.052 | 0 / −0.00205 |
| 24 – 30 | 0 | −52 | 30.000 | 29.948 | 0 | −0.052 | 0 / −0.00205 |
| 30 – 40 | 0 | −62 | 40.000 | 39.938 | 0 | −0.062 | 0 / −0.00244 |
| 40 – 50 | 0 | −62 | 50.000 | 49.938 | 0 | −0.062 | 0 / −0.00244 |
| 50 – 65 | 0 | −74 | 65.000 | 64.926 | 0 | −0.074 | 0 / −0.00291 |
| 65 – 80 | 0 | −74 | 80.000 | 79.926 | 0 | −0.074 | 0 / −0.00291 |
| 80 – 100 | 0 | −87 | 100.000 | 99.913 | 0 | −0.087 | 0 / −0.00343 |
| 100 – 120 | 0 | −87 | 120.000 | 119.913 | 0 | −0.087 | 0 / −0.00343 |
| 120 – 140 | 0 | −100 | 140.000 | 139.900 | 0 | −0.100 | 0 / −0.00394 |
| 140 – 160 | 0 | −100 | 160.000 | 159.900 | 0 | −0.100 | 0 / −0.00394 |
| 160 – 180 | 0 | −100 | 180.000 | 179.900 | 0 | −0.100 | 0 / −0.00394 |
| 180 – 200 | 0 | −115 | 200.000 | 199.885 | 0 | −0.115 | 0 / −0.00453 |
| 200 – 225 | 0 | −115 | 225.000 | 224.885 | 0 | −0.115 | 0 / −0.00453 |
| 225 – 250 | 0 | −115 | 250.000 | 249.885 | 0 | −0.115 | 0 / −0.00453 |
| 250 – 280 | 0 | −130 | 280.000 | 279.870 | 0 | −0.130 | 0 / −0.00512 |
| 280 – 315 | 0 | −130 | 315.000 | 314.870 | 0 | −0.130 | 0 / −0.00512 |
| 315 – 355 | 0 | −140 | 355.000 | 354.860 | 0 | −0.140 | 0 / −0.00551 |
| 355 – 400 | 0 | −140 | 400.000 | 399.860 | 0 | −0.140 | 0 / −0.00551 |
| 400 – 450 | 0 | −155 | 450.000 | 449.845 | 0 | −0.155 | 0 / −0.00610 |
| 450 – 500 | 0 | −155 | 500.000 | 499.845 | 0 | −0.155 | 0 / −0.00610 |
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 N9
N9 denotes a hole tolerance zone with tight transition deviation in the ISO 286 system.
At Ø25 mm N9 is 0 / −0.052 mm, i.e. 24.948 to 25.000 mm.
How the limits are calculated
N9 uses grade IT9 (a standard tolerance of 52 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); IT9 sets the width below ES. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.