Reading an ISO fit
Shop charts (Misumi / ISO 286) list a whole row of regularly used hole classes and shaft classes for each size band. Enter a nominal diameter and the calculator shows that row — B10, C9, F8, G7, H7, JS7, K7, P7 on holes; b9, g6, h7, k6, s6, u6 on shafts — with the same upper / lower micrometre pair as the printed table. Tap a cell for max, min and a diagram. Upper-case letters are internal (hole or pocket width). Lower-case letters are external (shaft).
The same ISO code produces the same micrometre limits on a hole and on a pocket of that width — 20 H8 is +33 / 0 µm whether it is a bore or a milled slot. The calculator still keeps the two as separate feature types because the usual grades are different: reamed holes are typically H7; milled pockets are typically H8–H11, not H7.
Formula
Max = nominal + ES (internal) or es (shaft)
Min = nominal + EI or ei
Mean = (max + min) / 2
IT7 ≈ 16i, where i = 0.45∛D + 0.001D (µm, D in mm)
Ø20 H7 hole
H7 hole tolerance chart
Common diameters people look up from a drawing. Each row is a reamed H7 bore — never under nominal. Open a row for the full ISO 286 notes and a diagram.
| Diameter | H7 limits | Deviation |
|---|---|---|
| Ø8 H7 | 8.000–8.015 mm | +15 / 0 µm |
| Ø10 H7 | 10.000–10.015 mm | +15 / 0 µm |
| Ø12 H7 | 12.000–12.018 mm | +18 / 0 µm |
| Ø16 H7 | 16.000–16.018 mm | +18 / 0 µm |
| Ø20 H7 | 20.000–20.021 mm | +21 / 0 µm |
| Ø25 H7 | 25.000–25.021 mm | +21 / 0 µm |
| Ø28 H7 | 28.000–28.021 mm | +21 / 0 µm |
| Ø30 H7 | 30.000–30.021 mm | +21 / 0 µm |
| Ø35 H7 | 35.000–35.025 mm | +25 / 0 µm |
| Ø40 H7 | 40.000–40.025 mm | +25 / 0 µm |
| Ø50 H7 | 50.000–50.025 mm | +25 / 0 µm |
| Ø65 H7 | 65.000–65.030 mm | +30 / 0 µm |
| Ø80 H7 | 80.000–80.030 mm | +30 / 0 µm |
| Ø100 H7 | 100.000–100.035 mm | +35 / 0 µm |
| Ø120 H7 | 120.000–120.035 mm | +35 / 0 µm |
Holes vs pockets vs shafts
- Hole — internal cylinder. Common: H7 (reamed), H8 (bored), H11 (drilled).
- Pocket / slot — internal width between two walls. Common: H8, H9, H11, H12. Not a different ISO table — the same internal letters — but listed separately so a pocket is never labelled as a hole.
- Shaft — external cylinder. Common: h6, h7, g6, k6, p6, s6. Never interchange h7 with H7.
How we use H7 in real toolmaking
On a die or mould, H7 is the reamed location hole — dowel, guide bush, bearing bore. The hole is allowed oversize by IT7, never undersize, so an h6 or g6 pin still enters. Milled pockets are H8–H11, not H7. This H7 tolerance chart covers an H7 bore at common diameters — 20 mm, 30 mm, 100H7, 120H7 — plus H7/g6 and other fits. Accurate Industries has used these ISO 286 classes on tooling in Pune for decades; this page is that chart with a diagram. Need to check the physical model dimensions? Open the CAD Viewer.
Common pairings
- H7/g6 — close running clearance (bearings that must spin by hand)
- H7/h6 — locational sliding
- H7/k6 — transition, may need a light press
- H7/p6 or H7/s6 — interference / press fits
- H8/f7 — easy running, more play
H7 and ISO class pages
- H7 hole tolerance
- h7 shaft (not H7)
- 8 mm H7 limits
- 10 mm H7 limits
- 12 mm H7 limits
- 16 mm H7 limits
- 20mm H7 hole limits
- 28H7 tolerance
- 30mm H7 tolerance
- 65H7 tolerance
- 100H7 tolerance
- 120H7 tolerance
- 6f7 tolerance
- 20 mm f7 shaft
- H6 hole
- H8 hole
- g6 shaft
- k6 tolerance chart
- p6 calculator
This page is an engineering tolerance calculator and ISO 286 tolerance calculator. Convert millimetres to inches with the unit converter, check a tapped hole with the thread calculator, or estimate stock with the material weight calculator.