What is DIN 7168 and How it Differs from ISO 2768
Those who have worked with engineering drawings for years may remember seeing a note on technical drawings that reads "General Tolerances According to DIN 7168." However, when looking at modern manufacturing drawings today, that same notation has largely been replaced with "ISO 2768-mK."
At first glance, the two standards may appear nearly identical because they serve a similar purpose in manufacturing design. When we examine their origin, structure, scope, and application, it becomes clear that DIN 7168 and ISO 2768 differ in several important ways.
Understanding these standards is especially important for manufacturers, design engineers, CNC machining companies, and quality control teams that regularly work with precision engineering drawings.
In this article, we will examine what each standard represents and where their similarities and differences exist.
What is DIN 7168?
DIN 7168 is a German engineering standard developed by Deutsches Institut für Normung (DIN), the national organization responsible for creating industrial standards in Germany.
The primary purpose of DIN 7168 was to define general tolerances for linear dimensions, angular dimensions, and geometrical tolerances without requiring engineers to specify tolerance values for every individual measurement shown on a technical drawing.
Instead of assigning separate tolerances to every feature, engineers could simply reference DIN 7168 within the title block, allowing the standard to automatically apply to all dimensions that did not have individually specified tolerances.
The standard was divided into two separate sections:
DIN 7168 Teil 1 — general tolerances for linear and angular dimensions
DIN 7168 Teil 2 — general tolerances for geometrical tolerances (form and position)
DIN 7168 dimensional tolerance classes
DIN 7168 Teil 1 defined four tolerance classes for linear and angular dimensions:
Class | German name | Meaning |
|---|---|---|
f | fein | Fine |
m | mittel | Medium |
g | grob | Coarse |
sg | sehr grob | Very coarse |
DIN 7168 geometrical tolerance classes
DIN 7168 Teil 2 defined geometrical tolerance classes using the letters H, K, and L, with H being the most precise and L the least.
One important fact to remember is that DIN 7168 is no longer an active engineering standard.
It was officially withdrawn in 1991 and replaced by the international ISO 2768 standard (adopted in Germany as DIN EN ISO 2768). Even DIN itself no longer recommends its use for modern engineering drawings. Today, its primary importance remains historical, particularly because older technical drawings and legacy industrial components may still reference this standard.
What is ISO 2768?
ISO 2768 is an internationally recognized engineering standard developed by the International Organization for Standardization (ISO).
It effectively replaced national standards such as DIN 7168 by providing a globally accepted tolerance system used across international manufacturing industries. In Germany and the European Union, the standard is commonly published and referenced as DIN EN ISO 2768.
Just like the earlier DIN standard, ISO 2768 simplifies technical drawings by eliminating the need to define tolerances for every individual dimension.
The standard is divided into two sections:
ISO 2768-1 defines general tolerances for linear and angular dimensions.
It includes four tolerance classes:
Fine (f)
Medium (m)
Coarse (c)
Very Coarse (v)
The second section, ISO 2768-2, defines geometrical tolerances, including form and position characteristics.
This section uses three tolerance classes:
H
K
L
When engineers use a notation such as ISO 2768-mK, it indicates that the drawing follows medium dimensional tolerance (m) from Part 1 and geometrical tolerance class K from Part 2.
This is one of the most commonly used tolerance combinations in modern manufacturing.
ISO 2768 is widely used across manufacturing operations involving:
CNC milling
CNC turning
Drilling
Grinding
Sheet metal fabrication
It is important to understand that ISO 2768 does not cover thread tolerances or surface roughness values. Those require separate standards — for example, ISO 965 for metric screw threads and ISO 1302 for surface texture notation.
If a specific dimension on a drawing includes its own tolerance value, that value always overrides the general ISO tolerance specification.
For full tolerance tables by dimension range, see our ISO 2768 Tolerance Charts.
Comparison Table: DIN 7168 and ISO 2768
Criteria | DIN 7168 | ISO 2768 |
|---|---|---|
Issuing Authority | German Institute for Standardization (Germany) | International Organization for Standardization |
Scope | National engineering standard mainly used in German manufacturing industries | International engineering standard accepted globally across manufacturing industries |
Current Status | Officially withdrawn in 1991 and superseded for new drawings | Active international standard currently used for new production drawings |
Standard Structure | Divided into Teil 1 (linear/angular) and Teil 2 (geometrical tolerances) | Divided into ISO 2768-1 for dimensions and ISO 2768-2 for geometrical tolerances |
Dimensional Tolerance Classes | f, m, g, sg (fine, medium, coarse, very coarse) | f, m, c, v (fine, medium, coarse, very coarse) |
Geometrical Tolerance Classes | H, K, L (defined in Teil 2) | H, K, L (defined in ISO 2768-2) |
Relationship Between Standards | Considered predecessor standard before ISO adoption | Developed as the international successor standard replacing older DIN systems |
German designation | Withdrawn; no longer published | Published as DIN EN ISO 2768 |
DIN 7168 to ISO 2768 Class Mapping
Because ISO 2768 was designed as the direct successor to DIN 7168, the tolerance classes map closely between the two standards:
DIN 7168 Teil 1 | ISO 2768-1 | Notes |
|---|---|---|
f (fein) | f (fine) | Identical tolerance values |
m (mittel) | m (medium) | Identical tolerance values |
g (grob) | c (coarse) | Identical tolerance values |
sg (sehr grob) | v (very coarse) | Identical tolerance values |
For geometrical tolerances, DIN 7168 Teil 2 and ISO 2768-2 use the same H, K, and L class designations with equivalent values.
This mapping is why a drawing updated from DIN 7168-mK to ISO 2768-mK does not change the allowable deviations — only the standard reference and international applicability change.
Where Both Standards Actually Intersect
This is often the area where confusion begins.
The numerical tolerance values assigned to the medium (m) and fine (f) classes within ISO 2768-1 are identical to the values originally used within DIN 7168 Teil 1. The same applies to the coarse classes: g in DIN maps to c in ISO, and sg maps to v.
In practical terms, this means that if an older drawing references DIN 7168 medium tolerance, and the same drawing is later updated using ISO 2768 medium tolerance, the allowable dimensional deviations remain exactly the same.
The actual difference lies not in the tolerance values themselves, but in the overall system structure and international applicability.
DIN 7168 was designed specifically for German manufacturing industries.
ISO 2768 was created to establish a universal engineering standard that manufacturers, suppliers, and customers across different countries could use without confusion.
How to Read Tolerance Notation on a Drawing
General tolerance notation typically appears in the title block or in a general note on the drawing. Common formats include:
Notation | Meaning |
|---|---|
ISO 2768-mK | Medium linear/angular tolerances (Part 1) + geometrical class K (Part 2) |
ISO 2768-fH | Fine linear/angular tolerances + geometrical class H (tightest) |
ISO 2768-cL | Coarse linear/angular tolerances + geometrical class L (loosest) |
DIN 7168-mK | Legacy notation; same m/K values as ISO 2768-mK, but references withdrawn standard |
The first letter after the hyphen refers to the dimensional tolerance class (f, m, c, or v). The second letter refers to the geometrical tolerance class (H, K, or L).
When reviewing legacy German drawings, you may also see older abbreviations such as DIN 7168 mittel or references to Teil 1 and Teil 2 separately rather than the combined notation used today.
Why These Standards Matter in Manufacturing Engineering
Although DIN 7168 is now obsolete, references to it still exist in real industrial environments.
Many older machine components, tooling systems, and industrial assemblies were originally designed decades ago and continue to use engineering drawings that reference DIN 7168.
Engineers responsible for maintenance, redesign projects, or reverse engineering often need to understand how these older tolerance systems work.
For new product development, however, the choice is straightforward.
Manufacturers today should use ISO 2768 (or DIN EN ISO 2768 in Germany) because it is internationally accepted and commonly used across machining, procurement, and global supply chain operations.
When updating older drawings, engineers frequently replace outdated DIN tolerance references with ISO 2768 to improve standardization. Because the tolerance values for equivalent classes are the same, this is often a straightforward title-block change rather than a full drawing revision.
That said, selecting the correct tolerance class remains extremely important.
Choosing unnecessarily tight tolerances may increase machining complexity, inspection time, and overall manufacturing cost.
On the other hand, tolerances that are too loose may create assembly problems and compromise product performance.
The tolerance specification shown in the drawing title block directly affects production cost, manufacturing efficiency, and product functionality.
Practical guidance for tolerance class selection
Application | Typical choice | Rationale |
|---|---|---|
General machined parts, sheet metal | ISO 2768-mK | Most common default; balances cost and fit |
Precision fits, tight assemblies | ISO 2768-fH or fK | Tighter deviations; higher machining cost |
Non-critical dimensions, rough castings | ISO 2768-cL or vL | Lower cost; wider acceptable variation |
Legacy drawing review | Match original DIN class (e.g. m → m, g → c) | Preserves original design intent |
Conclusion
DIN 7168 and ISO 2768 are closely related standards because ISO 2768 evolved directly from earlier engineering systems such as DIN 7168.
While DIN 7168 served German manufacturing industries successfully for many years, it was officially retired in 1991 and replaced by the internationally accepted ISO 2768 standard.
Many of the original tolerance values remained unchanged, but ISO 2768 introduced a clearer structure, renamed coarse classes (g/sg → c/v), and expanded global compatibility.
For modern manufacturers, understanding DIN 7168 remains useful when working with older engineering drawings.
For all new product development and precision manufacturing projects, ISO 2768 remains the preferred international standard used throughout modern engineering industries.