Tolerances according to ISO 2768

This standard provides exact tolerances for situations where no specific requirements are indicated on the drawing, supporting uniformity and efficiency.

Tolerances according to ISO 2768 in CNC Machining

For many customers, this standard is a reliable solution for less critical dimensions. At the same time, most customers work with detailed 2D drawings in PDF format, defining additional specifications for parts outside the standard. Here’s how ISO 2768 is applied, what tolerance levels are available, and when additional specifications on the drawing are necessary.

What is ISO 2768 and why is it relevant?

ISO 2768 is an international standard that describes specific tolerances for dimensions without explicit tolerances on the drawing. This ensures a uniform approach in production and lowers costs by reducing the need for inspection for non-critical dimensions. The standard is divided into two parts:

ISO 2768-1: For general tolerances on linear and angular dimensions.
ISO 2768-2: For tolerances to shape and location deviations.

By following this standard, we can produce parts efficiently and reliably. When precise tolerances are required, they can be recorded on the supplied 2D drawing.

ISO 2768-1: general tolerances for linear and angular dimensions

ISO 2768-1 provides a guideline for tolerances on linear and angular dimensions, with four tolerance levels: fine (f), medium (m), coarse (c), and very coarse (v).

Tolerance Levels and Applications

Tolerance level	Application	Example
F (fine)	For parts with high precision requirements	Precision components in medical equipment
M (medium)	For standard CNC parts	Housings and machine parts
C (coarse)	For less critical parts	Support structures and frames
V (very coarse)	For rough parts where precision is not required	Large industrial frames

Table for ISO 2768-1: Linear Dimensions (in mm)

Tolerance class	0.5 – 3 mm	> 3 – 6 mm	> 6 – 30 mm	> 30 – 120 mm	> 120 – 400 mm	> 400 – 1000 mm	> 1000 – 2000 mm	> 2000 – 4000 mm
F (fine)	±0,05	±0,05	±0,1	±0,15	±0,2	±0,3	±0,5	–
M (medium)	±0,1	±0,1	±0,2	±0,3	±0,5	±0,8	±1,2	±2,0
C (coarse)	±0,2	±0,3	±0,5	±0,8	±1,2	±2,0	±3,0	±4,0
V (very coarse)	–	±0,5	±1,0	±1,5	±2,5	±4,0	±6,0	±8,0

Table for ISO 2768-1: External Radii and Chamfer (in mm)

Tolerance class	0.5 – 3 mm	> 3 – 6 mm	> 6 mm
F (fine)	±0,2	±0,5	±1,0
M (medium)	±0,2	±0,5	±1,0
C (coarse)	±0,4	±1,0	±2,0
V (very coarse)	±0,4	±1,0	±2,0

Table for ISO 2768-1: Angular tolerances (in degrees and minutes)

Tolerance class	≤ 10 mm	> 10 – 50 mm	> 50 – 120 mm	> 120 – 400 mm	> 400 mm
F (fine)	±1°	±0°30′	±0°20′	±0°10′	±0°5′
M (medium)	±1°	±0°30′	±0°20′	±0°10′	±0°5′
C (coarse)	±1°30′	±1°	±0°30′	±0°15′	±0°10′
V (very coarse)	±3°	±2°	±1°	±0°30′	±0°20′

ISO 2768-2: tolerances for shape and location deviations

ISO 2768-2 describes tolerances for shape and location deviations such as flatness, parallelism and squareness. These tolerances are divided into three classes: H, K and L.

Tolerance Levels for Shape and Plate Tolerances.

Tolerance class	Application	Example
K (fine)	For precision parts with strict alignment	Precision assemblies
L (medium)	For most industrial applications	Industrial components with average tolerances
H (coarse)	For parts where tolerances are less important	Structural parts in heavy industry

Table for ISO 2768-2: Shape and Plate Tolerances (in mm)

Straightness and Flatness

Tolerance class	≤ 10 mm	> 10 – 30 mm	> 30 – 100 mm	> 100 – 300 mm	> 300 – 1000 mm	> 1000 – 3000 mm
H	0,02	0,05	0,1	0,2	0,3	0,4
K	0,05	0,1	0,2	0,4	0,6	0,8
L	0,1	0,2	0,4	0,8	1,2	1,6

Squareness

Tolerance class	≤ 100 mm	> 100 – 300 mm	> 300 – 1000 mm	> 1000 – 3000 mm
H	0,2	0,3	0,4	0,5
K	0,4	0,6	0,8	0,8
L	0,6	1,0	1,5	2,0

Symmetry

Tolerance class	≤ 100 mm	> 100 – 300 mm	> 300 – 1000 mm	> 1000 – 3000 mm
H	0,5	0,5	0,5	0,5
K	0,6	0,6	0,8	1,0
L	0,6	1,0	1,5	2,0

Battle

Tolerance class	Stroke
H	0,1
K	0,2
L	0,5

When are detailed 2D drawings in PDF format necessary?

ISO 2768 provides a solid basis for general tolerances, but there are situations where additional specifications are needed. Clients often provide detailed 2D drawings in PDF format that define precise tolerances and finishes. This is especially important in the following cases:

Critical dimensions and high precision
Surface roughness for visible parts
Materials and surface treatments
Specific fitting tolerances (such as H7/g6)
Geometric tolerances (GD&T).
Drill holes and threads
Chamfer and radii for functional or aesthetic details
Welding and assembly instructions

By providing detailed drawings, you can clearly define specific requirements so that the parts meet the functional and aesthetic requirements of your design.

Benefits of ISO 2768 tolerances for your project

Working to ISO 2768 allows us to produce cost-effectively without compromising on quality. Some of the advantages of applying this standard are:

Cost efficiency: Less critical dimensions require fewer checks, which increases production speed and reduces costs.
Consistency and reliability: Standard tolerances ensure uniform quality, which is particularly important for larger volumes or complex projects.
Efficient production process: Having to do fewer inspections on non-critical dimensions makes production more efficient, which minimizes errors.

Do you have specific needs?

Does your project have special tolerances or do your parts require higher precision than ISO 2768 offers? Feel free to contact us. We are happy to think with you about the best way to optimally prepare your 2D drawings so that together we can achieve the desired quality and accuracy.

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