ISO 286 · interference fit · IT6

s6 shaft tolerance

The s6 limits we cut to at every common nominal, computed from the ISO 286 fundamental deviation for s and the IT6 grade. Same numbers the configurator stamps on a s6 diameter.

s6 is an interference class: the whole band sits above nominal, so the shaft must be pressed or shrunk into a nominal-size bore. The letter s 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 s6 band is +.0019 to +.0014: the shaft measures between 1.0014″ and 1.0019″, a 0.0005″ window. The table gives the same limits at the inch and metric nominals we turn most.

Pick s6 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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s6 limits by nominal diameter

Nominal Ø	Upper dev.	Lower dev.	Max Ø (in)	Min Ø (in)	Band (in)
1/4″ (0.25)	+.0013	+.0009	0.2513	0.2509	0.0004
3/8″ (0.375)	+.0013	+.0009	0.3763	0.3759	0.0004
1/2″ (0.5)	+.0015	+.0011	0.5015	0.5011	0.0004
5/8″ (0.625)	+.0015	+.0011	0.6265	0.6261	0.0004
3/4″ (0.75)	+.0019	+.0014	0.7519	0.7514	0.0005
7/8″ (0.875)	+.0019	+.0014	0.8769	0.8764	0.0005
1″ (1)	+.0019	+.0014	1.0019	1.0014	0.0005
1-1/8″ (1.125)	+.0019	+.0014	1.1269	1.1264	0.0005
1-1/4″ (1.25)	+.0023	+.0017	1.2523	1.2517	0.0006
1-3/8″ (1.375)	+.0023	+.0017	1.3773	1.3767	0.0006
1-1/2″ (1.5)	+.0023	+.0017	1.5023	1.5017	0.0006
1-3/4″ (1.75)	+.0023	+.0017	1.7523	1.7517	0.0006
2″ (2)	+.0028	+.0021	2.0028	2.0021	0.0007
2-1/2″ (2.5)	+.0028	+.0021	2.5028	2.5021	0.0007
3″ (3)	+.0031	+.0023	3.0031	3.0023	0.0007
4″ (4)	+.0040	+.0031	4.004	4.0031	0.0009
Metric nominals (limits in inches)
20 mm (0.7874″)	+.0019	+.0014	0.7893	0.7888	0.0005
25 mm (0.9843″)	+.0019	+.0014	0.9861	0.9856	0.0005
30 mm (1.1811″)	+.0019	+.0014	1.183	1.1825	0.0005
35 mm (1.378″)	+.0023	+.0017	1.3803	1.3796	0.0006
40 mm (1.5748″)	+.0023	+.0017	1.5771	1.5765	0.0006
45 mm (1.7717″)	+.0023	+.0017	1.774	1.7733	0.0006
50 mm (1.9685″)	+.0023	+.0017	1.9708	1.9702	0.0006
55 mm (2.1654″)	+.0028	+.0021	2.1682	2.1674	0.0007
60 mm (2.3622″)	+.0028	+.0021	2.365	2.3643	0.0007
65 mm (2.5591″)	+.0028	+.0021	2.5619	2.5611	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 s6

Application	Finish target (Ra, µin)
Coupling, gear or pulley hub seat	16

Part of Shaft fits and tolerances. Other pages in the series: d9 · e8 · f7 · g6 · h6 · h7 · h8 · js6 · j6 · k5 · k6 · m6 · n6 · p6 · r6 · 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 s6 is used

These are the applications the configurator associates with s6, 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.

Interference fit, by the numbers

Every s6 limit is above nominal: against a nominal (H-basis) bore the shaft is oversize by 0.0014″ to 0.0019″ at 1″, before the bore's tolerance. Size the press force and hub stress from the maximum, and check the assembly can be done at all on larger diameters, where the interference grows.

Frequently Asked Questions

+.0019 to +.0014 from nominal: the shaft measures 1.0014″ to 1.0019″. The table above lists the same limits at every nominal from 1/4″ to 4″ and 20 to 65 mm.

s6 is an interference class on the shaft side. Against a nominal-size (H) bore it must be pressed or shrunk on. The mating bore's own class moves the result; this page is the shaft's half.

Coupling, gear or pulley hub seat: 16 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.