---
type: "fit-size"
designation: "g6"
nominal_size_mm: 8
feature: "shaft"
letter: "g"
it_grade: "ITIT6"
upper_deviation_um: -5
lower_deviation_um: -14
min_dia_mm: 7.986
max_dia_mm: 7.995
it_tolerance_um: 9
standard: "ISO 286-1:2010, ISO 286-2:2010"
verified: "August 1, 2026"
url: https://shopmath.org/fits/g6/8mm
---

# 8 mm g6 Tolerance — Limits, Deviations and Band

A 8 mm g6 shaft runs 7.986 to 7.995 mm — deviations -14 to -5 µm from nominal, on an ITIT6 band of 9 µm. Sliding shaft with minimal clearance — locates accurately and still moves freely.

- **Designation**: g6 at 8 mm
- **Feature**: shaft
- **Upper limit**: 7.995 mm (-5 µm)
- **Lower limit**: 7.986 mm (-14 µm)
- **Tolerance band**: 9 µm (ITIT6)
- **Fundamental deviation**: g — Sliding, small clearance
- **Standard**: ISO 286-1:2010, ISO 286-2:2010

## 8 mm g6 Limits

| Property | Micrometres | Millimetres |
| --- | --- | --- |
| Upper deviation | -5 | -0.005 |
| Lower deviation | -14 | -0.014 |
| Tolerance band (IT) | 9 | 0.009 |
| Maximum diameter |  | 7.995 |
| Minimum diameter |  | 7.986 |

_Deviations are measured from the nominal size. A diameter outside the two limits is a reject._

## Other Standard Tolerances at 8 mm

The other ISO 286 designations that carry a page at 8 mm — the comparison to make when g6 is the wrong fit.

| Designation | Feature | Lower deviation (µm) | Upper deviation (µm) | Min Ø (mm) | Max Ø (mm) | IT band (µm) |
| --- | --- | --- | --- | --- | --- | --- |
| [f7](https://shopmath.org/fits/f7/8mm.md) | shaft | -28 | -13 | 7.972 | 7.987 | 15 |
| [h6](https://shopmath.org/fits/h6/8mm.md) | shaft | -9 | +0 | 7.991 | 8.000 | 9 |
| [H7](https://shopmath.org/fits/h7/8mm.md) | hole | +0 | +15 | 8.000 | 8.015 | 15 |
| [h7](https://shopmath.org/fits/h7-shaft/8mm.md) | shaft | -15 | +0 | 7.985 | 8.000 | 15 |
| [p6](https://shopmath.org/fits/p6/8mm.md) | shaft | +15 | +24 | 8.015 | 8.024 | 9 |

## ISO 286 Standard Tolerance Grades at 8 mm

Every IT grade in the size band 8 mm falls in. The letter sets where the band sits; the IT grade sets how wide it is.

| Grade | Tolerance (µm) | Tolerance (mm) |
| --- | --- | --- |
| IT5 | 6 | 0.006 |
| IT6 | 9 | 0.009 |
| IT7 | 15 | 0.015 |
| IT8 | 22 | 0.022 |
| IT9 | 36 | 0.036 |
| IT10 | 58 | 0.058 |
| IT11 | 90 | 0.090 |
| IT12 | 150 | 0.150 |

## Sources and Method for 8 mm g6

### g6 at 8 mm

- **Source**: 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
- **Method**: computed
- **Verified against**: parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed

### Assumptions

- Values are the ISO 286-2 tabulated limits, not the ISO 286-1 formula: the formula deviates from the table by up to 13.26% and is carried only as a validation harness.
- Limits are at 20 °C, the ISO 1 reference temperature.
- ISO 286 tabulates per size band, so this value holds across the band the nominal size falls in.
- 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

## Common Questions About 8 mm g6

### What is the tolerance for a 8 mm g6 shaft?

A 8 mm g6 shaft is 7.986 to 7.995 mm — deviations -14 to -5 µm from nominal, a total tolerance band of 9 µm.

### What size reamer or bore does a 8 mm g6 shaft need?

Aim for the middle of the band: 7.990 mm, with 9 µm of total spread available between 7.986 and 7.995 mm.

### How much is 9 µm in millimetres and inches?

9 µm is 0.009 mm, or 0.00035 in.

## Related pages

- Smaller size: [6 mm g6](https://shopmath.org/fits/g6/6mm.md)
- Larger size: [10 mm g6](https://shopmath.org/fits/g6/10mm.md)
- All sizes of this tolerance: [g6 limits by size](https://shopmath.org/fits/g6.md)
- All fits and tolerances: [ISO 286 fit reference](https://shopmath.org/fits.md)
- Full grade table: [ISO 286 tolerance chart](https://shopmath.org/charts/iso-tolerances.md)

---

*Source: [ShopMath](https://shopmath.org/fits/g6/8mm) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*