What is the tolerance for 50 mm in ISO 2768-m?

±0.3 mm. A nominal 50 mm falls in the range over 30 up to 120 mm, where the medium class gives ±0.3 mm. In the fine class it would be ±0.15 mm.

What does ISO 2768-mK mean?

Medium (m) general tolerances for linear and angular dimensions from ISO 2768-1, and class K general geometrical tolerances from ISO 2768-2, for every feature without its own tolerance.

Which ISO 2768 class should I use?

Medium (m) with K is the usual choice for machined parts. Fine (f) with H is for precision machining, and coarse (c) or very coarse (v) with L for fabrications, castings and other parts where the process cannot hold tighter values.

ISO 2768 general tolerances: tables and lookup for f, m, c, v and H, K, L

The tolerances that apply to every dimension on a drawing that has no tolerance of its own. Enter a size and a class to get the limits, or read the tables below.

ISO 2768 tolerance for a nominal size

Nominal size (mm) Tolerance class

ISO 2768-1 tolerance chart for linear dimensions

Nominal size (mm)	ff fine	mm medium	cc coarse	vv very coarse
0.5 – 3	±0.05	±0.1	±0.2	–
3 – 6	±0.05	±0.1	±0.3	±0.5
6 – 30	±0.1	±0.2	±0.5	±1
30 – 120	±0.15	±0.3	±0.8	±1.5
120 – 400	±0.2	±0.5	±1.2	±2.5
400 – 1,000	±0.3	±0.8	±2	±4
1,000 – 2,000	±0.5	±1.2	±3	±6
2,000 – 4,000	–	±2	±4	±8

ISO 2768-1 external radii and chamfer heights

Nominal size (mm)	f	m	c	v
0.5 – 3	±0.2	±0.2	±0.4	±0.4
3 – 6	±0.5	±0.5	±1	±1
over 6	±1	±1	±2	±2

ISO 2768-1 angular tolerances

Shorter side (mm)	f	m	c	v
up to 10	±1°	±1°	±1°30′	±3°
10 – 50	±30′	±30′	±1°	±2°
50 – 120	±20′	±20′	±30′	±1°
120 – 400	±10′	±10′	±15′	±30′
over 400	±5′	±5′	±10′	±20′

ISO 2768-2 geometrical tolerances H, K and L

Straightness and flatness

Nominal size (mm)	H	K	L
up to 10	0.02	0.05	0.1
10 – 30	0.05	0.1	0.2
30 – 100	0.1	0.2	0.4
100 – 300	0.2	0.4	0.8
300 – 1,000	0.3	0.6	1.2
1,000 – 3,000	0.4	0.8	1.6

Perpendicularity

Shorter feature length (mm)	H	K	L
up to 100	0.2	0.4	0.6
100 – 300	0.3	0.6	1
300 – 1,000	0.4	0.8	1.5
1,000 – 3,000	0.5	1	2

Symmetry

Shorter feature length (mm)	H	K	L
up to 100	0.5	0.6	0.6
100 – 300	0.5	0.6	1
300 – 1,000	0.5	0.8	1.5
1,000 – 3,000	0.5	1	2

Circular run-out

H: 0.1 mm · K: 0.2 mm · L: 0.5 mm

Sources the values were checked against (10)

ISO 2768-mK: what the note on a drawing means

A title block note such as ISO 2768-mK calls up both parts of the standard at once. The lower-case letter is the class for linear and angular dimensions from part 1 (f fine, m medium, c coarse, v very coarse). The capital letter is the class for geometrical tolerances from part 2 (H, K or L). So mK means medium linear tolerances and class K for straightness, flatness, perpendicularity, symmetry and run-out. A note with only one letter, such as ISO 2768-m, applies part 1 alone.

General tolerances apply only where a dimension has no tolerance written next to it. Any toleranced dimension or geometrical tolerance on the drawing overrides them.

ISO 2768-1 and ISO 2768-2 today

ISO 2768-1:1989 is still the reference for general linear and angular tolerances. ISO 2768-2 has been withdrawn and replaced by ISO 22081, which no longer gives a table of values, so drawings that call up 2768-mK keep referring to the 1989 tables shown here. When you write the note on a new drawing, state the edition if your customer asks for it.

ISO 2768: common questions

What is the tolerance for 50 mm in ISO 2768-m?: ±0.3 mm. A nominal 50 mm falls in the range over 30 up to 120 mm, where the medium class gives ±0.3 mm. In the fine class it would be ±0.15 mm.
What does ISO 2768-mK mean?: Medium (m) general tolerances for linear and angular dimensions from ISO 2768-1, and class K general geometrical tolerances from ISO 2768-2, for every feature without its own tolerance.
Which ISO 2768 class should I use?: Medium (m) with K is the usual choice for machined parts. Fine (f) with H is for precision machining, and coarse (c) or very coarse (v) with L for fabrications, castings and other parts where the process cannot hold tighter values.