Shaft Tolerance Chart: g6, h6 & f7 Values (ISO 286)

The shaft tolerance chart is a key standard in the ISO fit system. Grades such as g, h and f define the allowed deviation of a shaft's size to ensure fit accuracy with the hole. Each band decides whether parts form a clearance, transition or interference fit. This guide covers shaft tolerance grades, code structure, size ranges and fit logic, with a full tolerance reference chart, to help engineers select the right fit in CNC machining and design.

1. What Shaft Tolerance Is

Shaft tolerance is the allowed variation of a shaft's actual size, controlling fit accuracy with the hole. In the chart, the top value is the upper limit and the bottom value the lower limit.

Shaft designations such as h7, g6 or f7 pair with hole tolerances under ISO 286; for hole values such as H7 or H8 see the Hole Tolerance Chart.

2. Code Structure

A shaft tolerance code is a letter (position) plus a number (precision):

The number is the IT grade: smaller number, higher precision, narrower band.

3. Shaft Tolerance Values (15 Common Grades, µm)

In each cell the upper figure is the upper deviation and the lower figure the lower deviation (µm; 1 µm = 0.001 mm); “>24–30” means over 24 mm up to 30 mm. Example: φ25 g6 falls in the >24–30 row at -7/-20 µm, i.e. 24.980–24.993 mm. Values follow the ISO 286 tolerance system; other grades such as b, c and d are in the chart image above this section.

h series (datum shaft, upper deviation 0)

e, f, g series (both deviations negative)

js, k, m, n series (js is symmetric: ± value only)

p, r, s series (both deviations positive; s6 listed up to 250 mm only)

4. g, f Series (Clearance Fit)

g series: shaft slightly smaller than the hole, for sliding fits. f series: smaller than g, larger clearance. In the tables g6 and f7 are negative deviations. The d, c, b series deviate more — the shaft is clearly below nominal, used where a large gap is needed, such as parts that grow with heat or must assemble easily. Press and shrink fits are interference fits at the other end of the scale (p, r, s…).

5. Fit Relationships (Hole vs Shaft)

A shaft tolerance only tells you the fit once it is paired with a hole tolerance: clearance, transition or interference. The definitions, common combinations and a worked φ25 example with actual limits are gathered in section 4 of ISO Fits Explained. One thing to keep in mind: the same code can land in a different fit type in a different size range (H7/p6 at 3 mm and below, for example, can open up a clearance), so always judge a fit together with its size range.

6. Size Range Effect

The band of the same grade widens with size: for h7 it is 10 µm up to 3 mm, 35 µm over 80 up to 100 mm and 63 µm over 450 up to 500 mm — the bigger the size, the wider the allowed machining error.

7. CNC Application Guide

To pick the shaft code from what the joint has to do (slide, locate or be pressed in), see sections 5 to 7 of ISO Fits Explained: based on the application examples in JIS B 0401, they list the shafts paired with an H7 hole from loose to tight and mark where parts become hard to dismantle without damage.

For matching hole tolerances see the Hole Tolerance Chart.

Shaft is within spec but it wobbles when it turns? That is orientation/runout tolerance at work — see the Geometric Tolerance Symbols Chart.

Thread tolerances are a separate system: they control pitch and minor diameters rather than hole or shaft sizes — see the Metric Thread Tolerance Chart.