ISO 286 · transition fit · IT6

n6 shaft tolerance

The n6 limits we cut to at every common nominal, computed from the ISO 286 fundamental deviation for n and the IT6 grade. Same numbers the configurator stamps on a n6 diameter.

n6 is a transition class: the band crosses or sits just above nominal, so the shaft is snug in a nominal-size bore and may need a light press. The letter n fixes where the band sits relative to nominal (the fundamental deviation); the grade 6 fixes how wide it is (IT6). Both come from the ISO 286 tables and scale with diameter, which is why one page per class, with every nominal, is more useful than a single number.

At a 1″ nominal the n6 band is +.0011 to +.0006: the shaft measures between 1.0006″ and 1.0011″, a 0.0005″ window. The table gives the same limits at the inch and metric nominals we turn most.

Pick n6 on any diameter in the configurator and the drawing carries exactly these limits; the engine computes them from the standard for the diameter you enter, not from this table.

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n6 limits by nominal diameter

Nominal Ø	Upper dev.	Lower dev.	Max Ø (in)	Min Ø (in)	Band (in)
1/4″ (0.25)	+.0007	+.0004	0.2507	0.2504	0.0004
3/8″ (0.375)	+.0007	+.0004	0.3757	0.3754	0.0004
1/2″ (0.5)	+.0009	+.0005	0.5009	0.5005	0.0004
5/8″ (0.625)	+.0009	+.0005	0.6259	0.6255	0.0004
3/4″ (0.75)	+.0011	+.0006	0.7511	0.7506	0.0005
7/8″ (0.875)	+.0011	+.0006	0.8761	0.8756	0.0005
1″ (1)	+.0011	+.0006	1.0011	1.0006	0.0005
1-1/8″ (1.125)	+.0011	+.0006	1.1261	1.1256	0.0005
1-1/4″ (1.25)	+.0013	+.0007	1.2513	1.2507	0.0006
1-3/8″ (1.375)	+.0013	+.0007	1.3763	1.3757	0.0006
1-1/2″ (1.5)	+.0013	+.0007	1.5013	1.5007	0.0006
1-3/4″ (1.75)	+.0013	+.0007	1.7513	1.7507	0.0006
2″ (2)	+.0015	+.0008	2.0015	2.0008	0.0007
2-1/2″ (2.5)	+.0015	+.0008	2.5015	2.5008	0.0007
3″ (3)	+.0015	+.0008	3.0015	3.0008	0.0007
4″ (4)	+.0018	+.0009	4.0018	4.0009	0.0009
Metric nominals (limits in inches)
20 mm (0.7874″)	+.0011	+.0006	0.7885	0.788	0.0005
25 mm (0.9843″)	+.0011	+.0006	0.9854	0.9848	0.0005
30 mm (1.1811″)	+.0011	+.0006	1.1822	1.1817	0.0005
35 mm (1.378″)	+.0013	+.0007	1.3793	1.3786	0.0006
40 mm (1.5748″)	+.0013	+.0007	1.5761	1.5755	0.0006
45 mm (1.7717″)	+.0013	+.0007	1.773	1.7723	0.0006
50 mm (1.9685″)	+.0013	+.0007	1.9698	1.9692	0.0006
55 mm (2.1654″)	+.0015	+.0008	2.1669	2.1661	0.0007
60 mm (2.3622″)	+.0015	+.0008	2.3637	2.363	0.0007
65 mm (2.5591″)	+.0015	+.0008	2.5606	2.5598	0.0007

Deviations from nominal in inches at 0.0001 in resolution; max and min are the finished diameter limits. Metric nominals are converted and the limits shown in inches.

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Applications and finish targets for n6

Application	Finish target (Ra, µin)
Bearing seat (inner ring on a rotating shaft)	32

Part of Shaft fits and tolerances. Other pages in the series: d9 · e8 · f7 · g6 · h6 · h7 · h8 · js6 · j6 · k5 · k6 · m6 · p6 · r6 · s6 · 1/4″ · 3/8″ · 1/2″ · 5/8″ · 3/4″ · 7/8″ · 1″ · 1-1/8″ · 1-1/4″ · 1-3/8″ · 1-1/2″ · 1-3/4″ · 2″ · 2-1/2″ · 3″ · 4″ · 20 mm · 25 mm · 30 mm · 35 mm · 40 mm · 45 mm · 50 mm · 55 mm · 60 mm · 65 mm.

Where n6 is used

These are the applications the configurator associates with n6, with the surface-finish target it applies to that diameter. A fit class sets size; the finish is what makes the size hold in service.

Transition fit, by the numbers

A n6 shaft against a nominal (H-basis) bore ranges from a slight clearance to a slight interference depending on where each part lands in its band; at 1″ the shaft itself spans 1.0006″ to 1.0011″. It seats without slop and still comes apart with an arbor press, which is the point.

Frequently Asked Questions

+.0011 to +.0006 from nominal: the shaft measures 1.0006″ to 1.0011″. The table above lists the same limits at every nominal from 1/4″ to 4″ and 20 to 65 mm.

n6 is a transition class on the shaft side. Against a nominal-size (H) bore it is snug and may need a light press. The mating bore's own class moves the result; this page is the shaft's half.

Bearing seat: 32 µin Ra. These are the targets the configurator applies when it recognises the application; you can override the finish on any diameter.

These references are for specifying a part; every value here is one the configurator applies when you build one. Numbers are representative of the standard; check them against your part and its mating components before ordering. See all guides on the guides page.