Reference
Tolerance chart — h9, h10 and h11
Enter your size and get the exact maximum and minimum. The full chart by size range is below, and it prints cleanly if you want it on the wall.
Diameter for round bar, across flats for hex
Falls in the over 18 to 30 mm band.
h9
19.948
to 20.000 mm
- Tolerance
- 52 µm
- Upper dev.
- 0.000
- Lower dev.
- -0.052
h10
19.916
to 20.000 mm
- Tolerance
- 84 µm
- Upper dev.
- 0.000
- Lower dev.
- -0.084
h11
19.870
to 20.000 mm
- Tolerance
- 130 µm
- Upper dev.
- 0.000
- Lower dev.
- -0.130
h9 — Closest
Specified where the bar is used with minimal machining, or where a close running or locational fit is needed. Typical for hydraulic rods and precision shafting.
h10 — Standard
The general purpose bright bar tolerance. Suits most turned components and bar-fed automatic work where a finishing cut follows.
h11 — Commercial
Economical, for general engineering and fabricated work where the bar will be machined all over or where fit is not critical.
Full tolerance chart
| Nominal size (mm) | h9 (µm) | h10 (µm) | h11 (µm) |
|---|---|---|---|
| over 0 to 3 | −25 | −40 | −60 |
| over 3 to 6 | −30 | −48 | −75 |
| over 6 to 10 | −36 | −58 | −90 |
| over 10 to 18 | −43 | −70 | −110 |
| over 18 to 30 | −52 | −84 | −130 |
| over 30 to 50 | −62 | −100 | −160 |
| over 50 to 80 | −74 | −120 | −190 |
| over 80 to 120 | −87 | −140 | −220 |
All values are negative deviations. In an ISO 286 ‘h’ fit the upper deviation is always zero, so the bar is never larger than the nominal size — it lies between nominal and nominal minus the tolerance. That is what lets a bar of nominal size always enter a collet or bush.
- What does the "h" in h9 mean?
- In ISO 286 a lower-case h means the upper deviation is zero. The bar is never larger than the nominal size — it lies between nominal and nominal minus the tolerance. That is what lets a bar of nominal size always enter a collet or bush of nominal size.
- What is the difference between h9, h10 and h11?
- The number is the IT grade — the width of the tolerance band. A lower number is tighter. At 20 mm, h9 is 52 microns, h10 is 84 microns and h11 is 130 microns. The band widens with size, so the exact value depends on your diameter.
- Which tolerance should I specify?
- Choose from your process, not from a preference for precision. h9 where the bar is used with minimal machining or needs a close running fit. h10 for general turned components where a finishing cut follows. h11 where the bar is machined all over or fit is not critical. If your first operation turns the diameter down anyway, h9 buys you nothing over h11.
- Does the tolerance apply across flats on hex bar?
- Yes. On hex bar the h-band is applied to the across-flats dimension.
Tell us what you need
Tell us the grade, size and tolerance band you need and we will confirm availability.