ISO 286 · shaft tolerance · IT6
k6 Tolerance — Shaft Limits by Nominal Size
https://shopmath.org/fits/k6 · data verified August 1, 2026
A 25 mm k6 shaft runs 25.002 to 25.015 mm — deviations of +2 to +15 µm on a tolerance band 13 µm wide. The k sets where the band sits (transition, light drive) and IT6 sets how wide it is. Transition shaft — accurate location, assembles and disassembles with light force. All values apply at 20 °C.
- Feature
- shaft
- Letter
- k
- Grade
- IT6
- Sizes
- 13
- Standard
- ISO 286-1:2010
k6 shaft at Ø25 mm · deviation, µm
+15 / +2
- Max Ø
- 25.015mm
- Min Ø
- 25.002mm
- Band
- 13µm
Deviations from the 25 mm nominal size, at 20 °C. Every other verified size is in the table below.
- Source
- ISO 286-1:2010, ISO 286-2:2010
- Formula
- max Ø = nominal + es min Ø = nominal + ei
- Assumptions
- Ø25 mm nominal, 18–30 mm size step, plain cylindrical feature, 20 °C. Deviations are tabulated in the standard and compiled here; the limits are those deviations added to the nominal size.
- Verified
- August 1, 2026
k6 Shaft Limits at Every Verified Nominal Size
Deviations in micrometres and finished limits in millimetres. These are the thirteen nominal sizes with verified demand; the deviation pattern continues across the full ISO 286 size range.
| Property | Deviation, µm | Limits, mm | Property | ||
|---|---|---|---|---|---|
| Nominal Ø | Upper | Lower | Min | Max | Tolerance band, µm |
| 5 mm | +9 | +1 | 5.001 | 5.009 | 8 |
| 6 mm | +9 | +1 | 6.001 | 6.009 | 8 |
| 8 mm | +10 | +1 | 8.001 | 8.010 | 9 |
| 10 mm | +10 | +1 | 10.001 | 10.010 | 9 |
| 12 mm | +12 | +1 | 12.001 | 12.012 | 11 |
| 16 mm | +12 | +1 | 16.001 | 16.012 | 11 |
| 20 mm | +15 | +2 | 20.002 | 20.015 | 13 |
| 25 mm | +15 | +2 | 25.002 | 25.015 | 13 |
| 30 mm | +15 | +2 | 30.002 | 30.015 | 13 |
| 40 mm | +18 | +2 | 40.002 | 40.018 | 16 |
| 50 mm | +18 | +2 | 50.002 | 50.018 | 16 |
| 80 mm | +21 | +2 | 80.002 | 80.021 | 19 |
| 100 mm | +25 | +3 | 100.003 | 100.025 | 22 |
Deviations are relative to the nominal size: positive is above it, negative below. Limits assume the ISO 286 reference temperature of 20 °C.
The IT6 Tolerance Grade in k6, Across ISO 286 Size Bands
The number in k6 is the IT grade, and it sets how wide the tolerance band is. The band widens with size — that is the whole point of a graded tolerance system.
| Nominal size band | Tolerance, µm | Tolerance, mm |
|---|---|---|
| over 0 to 3 mm | 6 | 0.006 |
| over 3 to 6 mm | 8 | 0.008 |
| over 6 to 10 mm | 9 | 0.009 |
| over 10 to 18 mm | 11 | 0.011 |
| over 18 to 30 mm | 13 | 0.013 |
| over 30 to 50 mm | 16 | 0.016 |
| over 50 to 80 mm | 19 | 0.019 |
| over 80 to 120 mm | 22 | 0.022 |
| over 120 to 180 mm | 25 | 0.025 |
| over 180 to 250 mm | 29 | 0.029 |
| over 250 to 315 mm | 32 | 0.032 |
| over 315 to 400 mm | 36 | 0.036 |
| over 400 to 500 mm | 40 | 0.040 |
Bands are open at the bottom and closed at the top: 'over 18 to 30 mm' includes 30 mm and excludes 18 mm.
Fundamental Deviation of the k shaft Tolerance in k6
The letter in k6 sets where the tolerance band sits relative to the nominal size: transition, light drive. The grade then adds the band width to that starting point.
| Nominal size band | Fundamental deviation, µm | Which limit it sets |
|---|---|---|
| over 3 to 6 mm | +1 | lower (ei / EI) |
| over 6 to 10 mm | +1 | lower (ei / EI) |
| over 10 to 18 mm | +1 | lower (ei / EI) |
| over 18 to 30 mm | +2 | lower (ei / EI) |
| over 30 to 40 mm | +2 | lower (ei / EI) |
| over 40 to 50 mm | +2 | lower (ei / EI) |
| over 50 to 65 mm | +2 | lower (ei / EI) |
| over 65 to 80 mm | +2 | lower (ei / EI) |
| over 80 to 100 mm | +3 | lower (ei / EI) |
| over 100 to 120 mm | +3 | lower (ei / EI) |
| over 120 to 140 mm | +3 | lower (ei / EI) |
| over 140 to 160 mm | +3 | lower (ei / EI) |
| over 160 to 180 mm | +3 | lower (ei / EI) |
| over 180 to 200 mm | +4 | lower (ei / EI) |
| over 200 to 225 mm | +4 | lower (ei / EI) |
| over 225 to 250 mm | +4 | lower (ei / EI) |
| over 250 to 280 mm | +4 | lower (ei / EI) |
| over 280 to 315 mm | +4 | lower (ei / EI) |
| over 315 to 355 mm | +4 | lower (ei / EI) |
| over 355 to 400 mm | +4 | lower (ei / EI) |
The fundamental deviation is the limit nearest the nominal size. For a hole it is the lower limit for letters A–H and the upper limit above that; the other limit follows from the IT grade.
Standard Fits That Use the k6 Tolerance
A tolerance on its own is half a fit. These are the standard ISO 286 pairs k6 appears in, with what each one is used for.
| Fit | Type | Basis | What it is for |
|---|---|---|---|
| H7/k6 | transition | hole basis | Locational transition. Accurate location, assembles with light force. |
Clearance, transition and interference are properties of the pair, not of either tolerance alone.
Sources and Method for the k6 Tolerance Data
- k6 limitscomputed
limits computed from the compiled ISO 286 tables: ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell
Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed
Computed from the standard's formulas, then checked against published tables.
- IT6 tolerance gradecompiled
ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell
Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed. Formula per ISO 286-1 standard tolerance factor and fundamental deviation formulas, used as a validation harness only per docs/research/data-sourcing.md §3.6
Compiled from independent public sources that agree cell-for-cell.
- k fundamental deviationcompiled
ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell
Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed
Compiled from independent public sources that agree cell-for-cell.
- Formula
Limits from the deviations, shaft tolerance
max Ø = nominal + es min Ø = nominal + ei es = upper deviation (µm) ei = lower deviation (µm)
The deviations are tabulated in ISO 286-2 and compiled here; the limits are those deviations added to the nominal size, which is why both columns are shown.
- Assumptions
- Values apply at the ISO 286 reference temperature of 20 °C.
- Limits are for a plain cylindrical feature. A tolerance letter says nothing about surface finish, form or roundness — those need their own callouts.
- Dataset scope: COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula.
- Data last verified
- August 1, 2026
How to Cite This k6 Tolerance Reference
Citation
ShopMath. "k6 Tolerance — Shaft Limits by Nominal Size." ShopMath, verified August 1, 2026, https://shopmath.org/fits/k6
BibTeX
@misc{shopmath-fits-k6,
title = {k6 Tolerance — Shaft Limits by Nominal Size},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/fits/k6}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/fits/k6
Common Questions About the k6 Tolerance
What is the tolerance of a 25 mm k6 shaft?
- A 25 mm k6 shaft runs 25.002 to 25.015 mm — deviations of +2 to +15 µm, a tolerance band 13 µm wide.
What does k6 mean?
- k6 is an ISO 286 shaft tolerance. The k sets the fundamental deviation — transition, light drive — and the 6 is the IT6 tolerance grade, which sets how wide the band is. Transition shaft — accurate location, assembles and disassembles with light force.
How wide is the IT6 tolerance band?
- IT6 is 13 µm wide for nominal sizes over 18 up to 30 mm, and widens with size — the full band table is on this page.
Which fits use k6?
- k6 appears in 1 standard ISO 286 fits: H7/k6 (transition).
k6 at Ø25 mm · µm
+15 / +2
25.002 – 25.015 mm