What is the tolerance for a 20 mm p6 shaft?

A 20 mm p6 shaft runs 20.022 to 20.035 mm — deviations of +22 to +35 µm, a band 13 µm wide.

What is the maximum and minimum size of a 20 mm p6 shaft?

Maximum 20.035 mm, minimum 20.022 mm. Anything outside that band is a reject at 20 °C, not a judgement call.

Why is the IT6 band 13 µm at 20 mm?

Because 20 mm falls in the ISO 286 size band over 18 up to 30 mm, and IT6 is defined per band rather than per size. Every nominal size in that band carries the same 13 µm width for IT6.

What shaft goes in a 20 mm p6 hole?

At 20 mm the standard pairs run from H7/h6 (0 to +34 µm clearance) through transition to interference fits — the full list with clearances is on this page.

What does the p in p6 mean?

Light interference. It fixes the fundamental deviation — the limit nearest the nominal size — while IT6 fixes the width of the band, which at 20 mm is 13 µm.

ISO 286 · p6 shaft · Ø20 mm

20 mm p6 Tolerance — Shaft Limits in mm and µm

https://shopmath.org/fits/p6/20mm · data verified August 1, 2026

A 20 mm p6 shaft is 20.022 to 20.035 mm — deviations of +22 to +35 µm on an IT6 band 13 µm wide. Light interference shaft for locational press fits in steel. Values apply at the ISO 286 reference temperature of 20 °C.

Nominal: 20 mm
Designation: p6
Feature: shaft
Grade: IT6
Band: 13 µm

20 mm p6 shaft · limits, mm

20.022 … 20.035

Upper dev: +35µm
Lower dev: +22µm
Band: 13µm

Measured at 20 °C on a plain cylindrical feature. The IT6 grade sets the 13 µm width; the p sets where the band sits.

Limits for a 20 mm p6 Shaft

Deviations in micrometres, finished limits in millimetres. Both describe the same band — the deviation is what a drawing carries, the limit is what a gauge reads.

20 mm p6 shaft tolerance — deviations and limits
Limit	µm	mm
Upper deviation	+35	0.035
Lower deviation	+22	0.022
Maximum diameter	+35	20.035
Minimum diameter	+22	20.022
Tolerance band (IT6)	13	0.013

Deviations are relative to the 20 mm nominal size. Values apply at the ISO 286 reference temperature of 20 °C; a part measured warm is not at these limits.

ISO 286 Tolerance Grades at 20 mm

20 mm falls in the ISO 286 size band over 18 to 30 mm, so every tolerance in that band has the same width regardless of which letter it carries.

ISO 286 standard tolerance grades at 20 mm nominal size
Grade	Tolerance, µm	Tolerance, mm
IT5	9	0.009
IT6	13	0.013
IT7	21	0.021
IT8	33	0.033
IT9	52	0.052
IT10	84	0.084
IT11	130	0.130
IT12	210	0.210

The grade sets the width of the band; the letter sets where that band sits relative to the nominal size.

Every Other ISO 286 Tolerance at 20 mm

The same nominal size under every other designation in this reference — the comparison that decides whether a feature is called out p6 or something looser.

ISO 286 hole and shaft tolerances at 20 mm nominal size
Property	Property	Deviation, µm		Limits, mm
Designation	Applies to	Upper	Lower	Min	Max
c11	shaft	-110	-240	19.760	19.890
d9	shaft	-65	-117	19.883	19.935
e8	shaft	-40	-73	19.927	19.960
f7	shaft	-20	-41	19.959	19.980
g6	shaft	-7	-20	19.980	19.993
h11	shaft	0	-130	19.870	20.000
h6	shaft	0	-13	19.987	20.000
h7	shaft	0	-21	19.979	20.000
h9	shaft	0	-52	19.948	20.000
k6	shaft	+15	+2	20.002	20.015
m6	shaft	+21	+8	20.008	20.021
n6	shaft	+28	+15	20.015	20.028
p6	shaft	+35	+22	20.022	20.035
r6	shaft	+41	+28	20.028	20.041
F8	hole	+53	+20	20.020	20.053
G7	hole	+28	+7	20.007	20.028
H11	hole	+130	0	20.000	20.130
H6	hole	+13	0	20.000	20.013
H7	hole	+21	0	20.000	20.021
H8	hole	+33	0	20.000	20.033
H9	hole	+52	0	20.000	20.052
K7	hole	+6	-15	19.985	20.006
N7	hole	-7	-28	19.972	19.993
P7	hole	-14	-35	19.965	19.986

Links go to that designation's page for this size where one exists, and to its full size table otherwise.

Standard Fits Available at 20 mm

What each standard hole/shaft pair gives at 20 mm, loosest first. Negative clearance is interference.

ISO 286 fits and their clearance at 20 mm nominal size
Property	Property	Clearance, µm		Property
Fit	Type	Min	Max	What it is for
H7/h6	clearance	0	+34	Locational clearance. Assembles by hand, no free movement intended.
H11/c11	clearance	+110	+370	Loose running. Wide commercial tolerances, large clearance for dirt, paint and thermal growth.
H9/d9	clearance	+65	+169	Free running. Good where accuracy is not essential and clearance can be generous.
H8/e8	clearance	+40	+106	Running fit with room for a lubricant film at speed.
H8/f7	clearance	+20	+74	Close running. The general-purpose lubricated journal fit.
H7/g6	clearance	+7	+41	Sliding. Locates accurately, still moves and turns freely.
H7/k6	transition	-15	+19	Locational transition. Accurate location, assembles with light force.
H7/m6	transition	-21	+13	Locational transition, tighter than k6.
H7/n6	transition	-28	+6	Tight transition. Usually a press job.
H7/p6	interference	-35	-1	Locational interference. Rigid location in steel without the load capacity of a drive fit.
H7/r6	interference	-41	-7	Medium drive. The joint itself carries load.
F8/h7	clearance	+20	+74	Close running, shaft basis.
G7/h6	clearance	+7	+41	Sliding, shaft basis. The h6 shaft is the reference and the hole carries the clearance.
K7/h6	transition	-15	+19	Locational transition, shaft basis.
N7/h6	transition	-28	+6	Tight transition, shaft basis.
P7/h6	interference	-35	-1	Locational interference, shaft basis.

Minimum clearance is the largest shaft in the smallest hole; maximum clearance is the smallest shaft in the largest hole.

Sources and Method for the 20 mm p6 Tolerance

20 mm p6 limitscomputed

limits computed from the compiled ISO 286 tables: ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell

Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed

Computed from the standard's formulas, then checked against published tables.

IT tolerance gradescompiled

ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell

Verified against parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed. Formula per ISO 286-1 standard tolerance factor and fundamental deviation formulas, used as a validation harness only per docs/research/data-sourcing.md §3.6

Compiled from independent public sources that agree cell-for-cell.

Formula

Limits from the deviations at 20 mm

max Ø  =  20 mm + (+35 µm)  =  20.035 mm
min Ø  =  20 mm + (+22 µm)  =  20.022 mm

The deviations are compiled from the ISO 286-2 tables; the limits are those deviations applied to the nominal size.

Assumptions

Values apply at the ISO 286 reference temperature of 20 °C.
Size only. Form, roundness, cylindricity and surface finish are separate callouts and a part inside these limits can still be unusable without them.
Dataset scope: COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula.

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This 20 mm p6 Tolerance Reference

Citation

ShopMath. "20 mm p6 Tolerance — Shaft Limits in mm and µm." ShopMath, verified August 1, 2026, https://shopmath.org/fits/p6/20mm

BibTeX

@misc{shopmath-fits-p6-20mm,
  title        = {20 mm p6 Tolerance — Shaft Limits in mm and µm},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/fits/p6/20mm}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/fits/p6/20mm

Common Questions About the 20 mm p6 Tolerance

What is the tolerance for a 20 mm p6 shaft?: A 20 mm p6 shaft runs 20.022 to 20.035 mm — deviations of +22 to +35 µm, a band 13 µm wide.
What is the maximum and minimum size of a 20 mm p6 shaft?: Maximum 20.035 mm, minimum 20.022 mm. Anything outside that band is a reject at 20 °C, not a judgement call.
Why is the IT6 band 13 µm at 20 mm?: Because 20 mm falls in the ISO 286 size band over 18 up to 30 mm, and IT6 is defined per band rather than per size. Every nominal size in that band carries the same 13 µm width for IT6.
What shaft goes in a 20 mm p6 hole?: At 20 mm the standard pairs run from H7/h6 (0 to +34 µm clearance) through transition to interference fits — the full list with clearances is on this page.
What does the p in p6 mean?: Light interference. It fixes the fundamental deviation — the limit nearest the nominal size — while IT6 fixes the width of the band, which at 20 mm is 13 µm.

All 13 p6 sizes · ISO 286 tolerance chart · Every designation and fit