H7/n6 fit: limit deviations and clearances (ISO 286)

Hole H7 with shaft n6, hole-basis system. Limit deviations and the resulting clearances for nominal sizes up to 500 mm, in micrometres. Transition fit at every size step below.

Nominal size (mm)		Hole H7 (µm)		Shaft n6 (µm)		Clearance (µm)		Fit
over	up to	ES	EI	es	ei	max.	min.
0	3	+10	0	+10	+4	+6	−10	Transition
3	6	+12	0	+16	+8	+4	−16	Transition
6	10	+15	0	+19	+10	+5	−19	Transition
10	18	+18	0	+23	+12	+6	−23	Transition
18	30	+21	0	+28	+15	+6	−28	Transition
30	50	+25	0	+33	+17	+8	−33	Transition
50	80	+30	0	+39	+20	+10	−39	Transition
80	120	+35	0	+45	+23	+12	−45	Transition
120	180	+40	0	+52	+27	+13	−52	Transition
180	250	+46	0	+60	+31	+15	−60	Transition
250	315	+52	0	+66	+34	+18	−66	Transition
315	400	+57	0	+73	+37	+20	−73	Transition
400	500	+63	0	+80	+40	+23	−80	Transition

Max. clearance = ES − ei, min. clearance = EI − es; a negative clearance is an interference. Above 500 mm MechPilot’s data holds no fundamental deviations, so no values are shown.

Example: ⌀25 H7/n6

Hole ⌀25 H7: 25.000 to 25.021 mm
Shaft ⌀25 n6: 25.015 to 25.028 mm

How the values are computed

Each deviation comes from the standard tolerance grade (IT) of the class and its fundamental deviation for the size step, combined by these rules of ISO 286-1:

Holes A to H: the fundamental deviation is the lower deviation EI (positive or zero); ES = EI + IT. ISO 286-1:1988, 9.2 and Figure 18.
Shafts k to zc: the fundamental deviation is the lower deviation ei (positive or zero); es = ei + IT. ISO 286-1:1988, 9.1 and Figure 17.

ISO fits explained · ISO 286 standard tolerance grades IT01 to IT18

Other fits

H11/c11 H9/d9 H8/f7 H7/g6 H7/h6 H7/js6 H7/k6 H7/p6 H7/s6 H7/u6

Source and verification

Standard

ISO 286-1:2010 Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 1: Basis of tolerances, deviations and fits; ISO 286-2:2010 Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts

Verification

primary (the standard’s own text was seen)

Verified from

https://cdn.standards.iteh.ai/samples/54915/7d6147c29fed4e31af36b60561e88752/ISO-286-2-2010.pdf (ISO 286-2:2010 preview: Table 1; Tables 2 and 3 for holes A to E)
https://law.resource.org/pub/in/bis/S01/is.919.1.1993.pdf (IS 919 (Part 1):1993, identical with ISO 286-1:1988: clause 9, Tables 2 and 3, Annex A)
https://cdn.standards.iteh.ai/samples/45975/c0a5df14167f48eebc6c17dc4da5f9c4/ISO-286-1-2010.pdf (ISO 286-1:2010 preview: terms and definitions only, no tables)

Verification notes

itGrades: ISO 286-2:2010 Table 1 (reproduced there from ISO 286-1:2010), read from the standard's own preview on 2026-10-22. IT01 and IT0 are not given above 500 mm (null).
fundamentalDeviations: read from ISO 286-1:1988 Tables 2 (shafts) and 3 (holes) in the identical Indian adoption IS 919 (Part 1):1993. The 2010 edition's Tables 2 and 3 were not seen. Holes A, B, C, D and E were cross-checked against ISO 286-2:2010 Tables 2 and 3 (lower limit deviations EI) and agree for every size step up to 500 mm. The other letters come from the 1988 edition only (see docs/to-verify.md).
The Delta values equal IT(n) - IT(n-1) of itGrades for every step above 3 mm; scripts/check-library.mjs checks this.

Tolerance grades

ISO 286-2:2010, Table 1 "Values of standard tolerance grades for nominal sizes up to 3 150 mm" (from ISO 286-1:2010, Table 1). Converted to mm; one value per entry of sizeSteps (main-step values repeated over their intermediate steps).

Fundamental deviations

ISO 286-1:1988, Table 2 (shafts: upper deviation es for a to h, lower deviation ei for k to zc) and Table 3 (holes: lower deviation EI for A to H, upper deviation ES for K to ZC), in mm with sign. Arrays follow sizeSteps; null = blank in the table, or not stored (every value above 500 mm is left out here).

Data file

library/fits/iso-286.json

Values that could not be checked against the standard are left out and listed in docs/to-verify.md. Check the standard itself before you rely on a value for production, and report any mistake on GitHub. to-verify.md · Issues