ISO 2768: A Guide to Tolerance Standards for CNC Machining

The ISO 2768 standard is a comprehensive set of specifications adopted by the International Organization for Standardization to enable uniformity and accuracy for different segments of the manufacturing process detailed in the technical drawings.

Table of Contents

What Is ISO 2768?

iso 2768-mk
iso 2768-mk

ISO 2768 has been issued by the International Organization for Standardization (ISO). It provides the layout of tolerances on engineering drawings. This is called surface roughness. Its goal is to ensure quality. It mainly applies to machined parts and removed materials. The ISO standard 2768 is applied where drawings give no specific tolerances. It applies to both machined and molded parts.

The standard has two sections. ISO 2768-1 is for data equipment for use in public data sync. ISO 2768-2 is the interface to management info. ISO 2768-1 sets general tolerances for sizes and angles of parts. It has four levels: silk (s), cotton (c), medium hairy (m), and imbricate (i). ISO 2768-2 covers geometric tolerances for features. They are sorted into three tolerance classes: H, K, and L. For example, ISO/2768-mK marks a component that must meet these requirements. This refers to “medium” tolerances from part one and class “K” from part two.

It enables us to keep technical drawings easy to share and understand. It lets us share and understand production processes internationally. This leads to more collaboration and better control.

ISO 2768 Part 2: Geometrical Tolerances for Features

ISO 2768 Part 1 is focused on establishing general tolerances for linear and angular dimensions, as well as external radii and chamfer heights. This part of the standard is crucial for ensuring uniformity in mechanical components where precise dimensions are pivotal.

Table 1: Tolerances for Linear Dimensions

ISO 2768 Part 1 categorizes tolerances into four classes based on precision requirements: fine (f), medium (m), coarse (c), and very coarse (v). These classifications help in setting appropriate limits for various manufacturing processes and are especially relevant for parts produced through machining or sheet metal fabrication.

Nominal Feature Length (mm)Fine (f)Medium (m)Coarse (c)Very Coarse (v)
0.5 to 3±0.05±0.1±0.2
over 3 to 6±0.05±0.1±0.3±0.5
over 6 to 30±0.1±0.2±0.5±1.0
over 30 to 120±0.15±0.3±0.8±1.5
over 120 to 400±0.2±0.5±1.2±2.5
over 400 to 1000±0.3±0.8±2.0±4.0
over 1000 to 2000±0.5±1.2±3.0±6.0
over 2000 to 4000±2.0±4.0±8.0

For dimensions smaller than 0.5 mm, specific deviations need to be indicated directly next to the relevant nominal size on technical drawings.

Table 2: Tolerances for Angular Dimensions

Angular dimensions are also subject to tolerances, which are crucial for ensuring the angular accuracy of fabricated parts. These tolerances are specified in degrees and minutes, reflecting the angular precision required in various applications.

Nominal Dimension Range (shortest side in mm)Fine (f)Medium (m)Coarse (c)Very Coarse (v)
up to 10±1°±1°±1°30′±3°
over 10 to 50±0°30′±0°30′±1°±2°
over 50 to 120±0°20′±0°20′±0°30′±1°
over 120 to 400±0°10′±0°10′±0°15′±0°30′
over 400±0°5′±0°5′±0°10′±0°20′

General Tolerances on External Radii and Chamfer Heights

For external radii and chamfers, ISO 2768 Part 1 also provides general tolerances. These are crucial for features that affect assembly and aesthetic aspects of parts.

Table 3: Tolerances for External Radii and Chamfer Heights

Nominal Feature Length (mm)Fine (f)Medium (m)Coarse (c)Very Coarse (v)
0.5 to 3±0.2±0.2±0.4±0.4
over 3 to 6±0.5±0.5±1.0±1.0
over 6±1.0±1.0±2.0±2.0

Application and Importance

It is important for industries that need precise details. These include aerospace, automotive, and medical device makers. It provides a common standard to reference it by, engineering and designers. Accordingly, most parts are compatible, as component sizes don’t vary that much.

The standard is introduced to simplify the design process. It does this by cutting unneeded wires. This change also makes the construction inspection stage easier. By analyzing the right tolerance class, manufacturers can strive to make their production systems more efficient. They can also keep control of manufacturing costs and maintain product quality.

ISO 2768 Part 2: Geometrical Tolerances for Features

ISO 2768 Part 2 is designed to establish a framework for geometrical tolerances in manufacturing, providing a simplified approach to specifying allowable deviations for features without individual tolerance indications on design drawings.

Table 4: General Tolerances on Straightness and Flatness

This table specifies the permissible deviations for straightness and flatness based on the nominal lengths in millimeters. These tolerances ensure that surfaces are even and straight to a specified degree, critical in maintaining structural integrity and function.

Ranges of Nominal Lengths in mmTolerance Class HTolerance Class KTolerance Class L
Up to
10 to 300.050.10.2
30 to 1000.10.20.4
100 to 3000.20.40.8
300 to 10000.30.61.2
1000 to 30000.40.81.6

Table 5: General Tolerances on Perpendicularity

These tolerances regulate the perpendicularity between features, ensuring components maintain accurate angular relationships which are crucial for assembly and function.

Ranges of Nominal Lengths in mmTolerance Class HTolerance Class KTolerance Class L
Up to 1000.20.40.6
100 to 3000.30.61.0
300 to 10000.40.81.5
1000 to 30000.51.02.0

Table 6: General Tolerances on Symmetry

Symmetry tolerances ensure that two features on a part are uniform across a datum plane, facilitating proper alignment and function in the assembly of parts.

Ranges of Nominal Lengths in mmTolerance Class HTolerance Class KTolerance Class L
Up to 1000.50.60.6
100 to 3000.50.61.0
300 to 10000.50.81.5
1000 to 30000.51.02.0

Table 7: General Tolerances on Circular Run-Out

Circular run-out tolerances are essential for components that must maintain precise rotational symmetry to function correctly, reducing vibrations and wear during operation.

Ranges of Nominal Lengths in mmTolerance Class HTolerance Class KTolerance Class L

Application and Importance

The ISO 2768 Part 2 has been found to be a critical for industries with the geometrical precision like aerospace, automotive, and manufactured goods, where intelligently made components are very significant. That is to say it makes possible manufacturing tolerance adjustments, which is what ensures that parts fit together and switch on properly. This standardization of geometric tolerance level, undeniably, performs better than generic approaches in mass manufacturing operations. This helps in ensuring better efficiency, eliminates errors and control quality.

What industries is ISO 2768 relevant to?

metric tolerance standards
metric tolerance standards

ISO 2762 is a worldwide standard for all industries. It is used for the global production of accurate and consistent goods and services. Multi-sectorally, it’s a very vital factor that enhances production quality and size consistency. Notable sectors include:

  • Aerospace: Good aerospace components are crucial. They ensure the sector’s credibility and efficiency. The ISO 2768 standard represents the tool to keep the quality high.
  • Automotive: This standard ensures smooth manufacturing. It allows for easy assembly in other areas where those parts are made locally.
  • Medical Devices: Consistency is crucial. The ISO 2768 standard helps manufacturers assure thoroughness by marking off a device’s means.
  • Electronics: Making a perfect layout or connection between the components is key. ISO 2768 must be a priority before an electronic product can work well.
  • Mechanical Engineering Services: Standardization is key in mechanical engineering. It keeps the specified precision needed to solve issues with machinery and components. Without it, the proper functioning of machinery and components would suffer.
  • Manufacturing: ISO 2768 finds its relevance in the manufacturing divisions including car manufacturing, aero sectors, and electronics engineering, taking care of inter changeability of parts and production consistency.
  • Industrial Design: It provides rules for the defining of the tolerances drawings to assure that the product is designed to perform the intended position it is created.
  • Tooling and Mold Manufacturing: It spans most industries. It specifies the allowances for molds/tooling. They must be within the tolerance level. This ensures the parts are within the required precision.

ISO 2768 is the international standard. It sets general tolerances for dimensional variation. These variations lack particular tolerance indicators. The standard closes the global manufacturing gap. This regulation decreases clarity in engineering drawings. It causes misunderstandings for rapid manufacturers. This would save waste and increase their capacity as they follow the given plan.

The Importance of ISO 2768 in Manufacturing

The ISO 2768 standard is vital in orthopedics. It simplifies technical drawings for manufacturers worldwide. It brings harmony to size limits. This will help makers and designers worldwide. It does so by using a standard approach. ISO 2768 will rely less on individual judgments for each dimension. It has set manufacturing tolerances. This continues to be easier and faster than specifying tolerances for each component.

The use of ISO standard 2768 can be seen as one way to remove the ambiguities in manufacturing. It does this by providing a common way to report dimensions. This has the effect that members must meet the set quality standards. They fit together well despite the manufacturer’s location. Accordingly, it also assures against expensive errors and creates a smooth environment of workflow.

What Are the ISO 2768 Accrediting Bodies, Audit Criteria, and Processes?

iso 2768 tolerances
iso 2768 tolerances

Accrediting Authorities for ISO 2768

Since ISO 2768 does not mean certification, therefore, neither a body is engaged in issuing certificates specifically for it. It is ISO through which the standard is founded and governed. It is a non-governmental and international organization. It was established by the national standards bodies. They are located worldwide. The ISO is making it easier for the arrival and spread of standards. They do this through their work on standards development and dissemination in all sectors and fields.

ISO 2768 audit criteria

ISO 2768 is not related to sales of certificates. Therefore, it does not contain categories for auditing. This standard is a document with instructions concerning the size variations of linear and angular dimensions figures in the technical drawings. ISO 2768 is usually confirmed through self-declaration. This is by organizations or people who use it in interior design or manufacturing.

ISO 2768 Auditing & Accreditation Procedure

The certification standard ISO 2768 does not have an audit or accreditation process linked to it, per say. Despite the fact that ISO standards like ISO 9001 also may require actors to use ISO 2768 limits, they do not provide a large range of variation. These SSIs tend to come with the auditing and certification procedures as well. These can be categorized into three main types:These can be categorized into three main types:

  • First-Party Audit (Internal Audit): This audit is done inside to check compliance with ISO standards like ISO 9001, ISO 14001, or ISO 45001. It compares to show where to improve. For example, in management, quality, risk assessment, paperwork, resources, and operations.
  • Second-Party Audit (Supplier Audit): The purchaser conducts this upon a supplier. It finds the key products he offers and their effect on the purchaser’s operations. Most of the times it is in ISO or as conforms to the buyer requirement.
  • Third-Party Audit (Certification Audit): An accredited body conducts such an audit to deliver assist organizations in achieving ISO certification. It consists of 1st 1st step of standard operating procedures approval registration and a third stringent compliance check. The company is granted an ISO certificate valid for three years. It needs to be checked each year by a surveillance audit. Then, it will be audited again after three years.

Accreditation for ISO 2768 Accreditation we are not present as ISO 2768 does not have any certification specific as such, but we are recognized in the international ISO market. ISO is a rare, non-governmental international organization. It is made up of national bodies. They manage the standard, an independent agency. ISO makes and spreads many standards. They serve different purposes and are used widely in industries and science.


The Latest Revision PDF of ISO 2768 for download.

What does ISO 2768-mK mean?

ISO 2768-mK says a part must stick to medium tolerance for Part 1 and the ‘K’ class for Part 2. It also has fine, coarse, and very coarse for Part 1. And, H, K, and L for Part 2.

Similar Certifications and Accreditations to ISO 2768.

The ISO 2768 standard gives tolerances for technical drawings. Other standards, such as ISO 9001, ISO 14001, ISO/IEC 17025, AS9100, ISO/TS 16949, and ISO 13485, provide frameworks for managing quality and the environment. They also have specific requirements for industries like aerospace, automotive, and medical devices.


Being ISO 2768 standardized streamlines global manufacturing processes through the uniformity of tolerances, increased product interconnectivity, and maintaining quality standards that are applicable in diverse industries. This uniformity tool is thus a necessity for engineers and manufacturers.

Collaborate with us so that ISO 2739 specifications be part of your production line-up and you realize the perfection in precision and quality in manufacturing. It is our hope to create a world of better products with you.


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