g6 shaft tolerance (IT6)

Lower-case g6 is an ISO 286 shaft tolerance class (IT6, es −2 … −20 µm): at Ø10 mm the deviations are −0.005/−0.014 mm, at Ø25 mm −0.007/−0.020 mm (upper/lower). Looking for the G6 hole?

Shaft tolerance class g6 per ISO 286-1:2010: fundamental deviation es −2 … −20, grade IT6 (6 µm at ≤ 3 mm to 40 µm at 400–500 mm). For an exact size, open the calculator with g6 selected.

Type
Shaft
Grade
IT6
Tolerance
6 … 40 µm
Fund. deviation
es −2 … −20 µm

g6 limits by size range

Size (mm)Upper (µm)Lower (µm)Ø max (mm)Ø min (mm)
≤ 3−2−82.9982.992
3 – 6−4−125.9965.988
6 – 10−5−149.9959.986
10 – 14−6−1713.99413.983
14 – 18−6−1717.99417.983
18 – 24−7−2023.99323.980
24 – 30−7−2029.99329.980
30 – 40−9−2539.99139.975
40 – 50−9−2549.99149.975
50 – 65−10−2964.99064.971
65 – 80−10−2979.99079.971
80 – 100−12−3499.98899.966
100 – 120−12−34119.988119.966
120 – 140−14−39139.986139.961
140 – 160−14−39159.986159.961
160 – 180−14−39179.986179.961
180 – 200−15−44199.985199.956
200 – 225−15−44224.985224.956
225 – 250−15−44249.985249.956
250 – 280−17−49279.983279.951
280 – 315−17−49314.983314.951
315 – 355−18−54354.982354.946
355 – 400−18−54399.982399.946
400 – 450−20−60449.980449.940
450 – 500−20−60499.980499.940

Deviations at the upper end of each range (Ø columns use that size); use the calculator for the exact size. — : not defined by ISO 286 for that size. Upper/Lower (mm) and inch columns are shown on wider screens.

About g6

g6 denotes a shaft tolerance zone with sliding deviation in the ISO 286 system. It is used in H7/g6 (Precision sliding parts that must move without perceptible play: spindles, sliding gears, guide pins, plungers.).

At Ø25 mm g6 is −0.007 / −0.020 mm, i.e. 24.980 to 24.993 mm.

How the limits are calculated

g6 uses grade IT6 (a standard tolerance of 13 µm at 18–30 mm). Fundamental deviation: es is tabulated directly by ISO 286-1 Table 2; ei = es − IT6. See the fundamental deviation table for every letter. Values per ISO 286-1:2010.

g6 in practice

Where it's used

g6 is the sliding-fit shaft. In an H7 bore it gives a small but guaranteed clearance, so parts move without perceptible play. Typical g6 parts are guide pins and plungers, spindles in sliding bearings, sliding gears and clutch sleeves, and precision linear shafts, which are commonly offered in g6 or h6. IT6 usually means a ground or very finely turned surface.

How to check it

Use a micrometer reading to 1 µm, or a snap gauge with GO at the upper limit. At IT6, temperature matters: a 25 mm steel shaft grows about 3 µm for every 10 °C, nearly a quarter of its 13 µm band. Measure at, or correct to, the 20 °C reference temperature of ISO 1, and let ground parts cool first.

Easily confused with

h6 sits right at the nominal size, so H7/h6 can assemble with zero clearance, while g6 always leaves a few micrometres. G6 in capitals is the hole class. On drawings, 25g6 and Ø25 g6 mean the same thing: ISO 286-1 writes the size first and the class directly after it.

Worked example

At Ø25 mm, g6 is −0.007/−0.020 mm (24.980–24.993 mm). In an H7 bore (25.000–25.021 mm) the clearance is 0.007–0.041 mm: never zero, and small enough that a guide pin locates to within a few hundredths of a millimetre.

Fits using g6

H7/g6All fits →

Related classes

g5g7G6