ISO 286 · 25 mm nominal (0.9843″)

25 mm shaft tolerances, every fit class

Every ISO 286 shaft class at a 25 mm nominal, computed for exactly this diameter: the limits the configurator stamps when you pick a class on a 25 mm seat, the IT grade widths behind them, and the tolerance the bar itself arrives in.

At a 25 mm nominal (0.9843″) ISO 286 places the diameter in its over 18 to 30 mm size step, so every class on this page takes its width from one row of the IT table: IT5 is 0.0004″, IT6 0.0005″, IT7 0.0008″ wide here. The letter then decides where that band sits against 0.9843″.

The tightest class on the page is k5 at 0.0004″; the widest is d9 at 0.0020″. The lowest limit on the page is 0.9796″ (d9 minimum) and the highest 0.9861″ (s6 maximum): a 0.0065″ spread between the loosest clearance and the heaviest press fit at this one diameter.

Pick any of these classes on a 25 mm diameter in the configurator and the drawing carries exactly these limits; the engine computes them from the standard for the diameter you enter, so a nominal between the sizes in this series resolves the same way.

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Every fit class at 25 mm

Deviations from the 0.9843″ nominal in inches at 0.0001 in resolution; max and min are the finished diameter limits. The 25 mm nominal is converted and every limit is shown in inches.

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IT grade widths at 25 mm

Band width (upper minus lower) of the h class at each grade. The letter of a class only moves the band; the grade alone sets how wide it is, so these widths apply to every class on this page.

As-supplied bar tolerance at 25 mm

Mill tolerance of the round bar as it arrives from the mill, for the grades the configurator offers. A fit class is cut to the limits above regardless; only a diameter left as supplied under a mill-finish OD carries the bar tolerance.

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 · 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 · 30 mm · 35 mm · 40 mm · 45 mm · 50 mm · 55 mm · 60 mm · 65 mm.

Clearance, transition and interference at 25 mm

Against a nominal 0.9843″ (H-basis) bore the clearance classes always leave a gap: f7 at least 0.0008″, g6 at least 0.0003″, while h6 and h7 touch nominal on the high side and leave a gap only as the shaft runs toward its minimum (0.9837″ for h6, 0.9834″ for h7).

The transition classes cross nominal: js6 is ±0.0003″, k5 runs +.0001 to +.0004, k6 +.0001 to +.0006; snug in a nominal bore, still off with an arbor press.

The interference classes are oversize throughout: p6 by 0.0009″ to 0.0014″, s6 by 0.0014″ to 0.0019″, before the bore's own tolerance is added. Size press force and hub stress from the maximum.

Fit class versus bar tolerance

The bar a 25 mm shaft is turned from has its own mill tolerance, listed in the third table. Cold-finished low-carbon steel bar (1018, 12L14) arrives at +.0000/-.0020 at this size, a 0.0020″ band, which is 3.9 times the IT6 width of 0.0005″.

A fit class is cut, so the bar's band never reaches the finished diameter. It matters for one case: a round diameter equal to the bar size and left as supplied under a mill-finish OD. That surface keeps the mill's tolerance and finish, and the drawing calls it out as the bar tolerance rather than a fit class.

Related: All fit classes · Surface finish reference · Pump shafts · Motor shafts.

Frequently Asked Questions

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.