Understanding ISO 2768 Tolerance — More Than Just Error Margins, It’s the Global Language of Manufacturing
- 翰君 陳
- Nov 5
- 3 min read
On engineering drawings, we often see numbers like “±0.1” or “±0.05” written beside dimensions.These represent tolerance — the allowable deviation in size.But when a drawing contains hundreds or even thousands of dimensions, specifying every single tolerance individually becomes time-consuming and prone to error or omission.
To help designers, manufacturers, and inspectors interpret allowable deviations consistently, the ISO 2768 international tolerance standard was created.
Left: Each dimension carries its own individual tolerance.
Right: With the unified notation “ISO 2768-mK,” the drawing becomes cleaner and communication clearer.
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Why Is ISO 2768 Important?
The core philosophy of ISO 2768 is simple: you don’t need to label a tolerance for every dimension.It provides a universal guideline so that by simply noting “ISO 2768-mK” on the drawing, all unspecified dimensions automatically follow defined tolerance limits.
This approach brings three key advantages:
Fewer mistakes and omissions – drawings look cleaner and communication is more consistent.
Manufacturing and inspection alignment – different factories follow the same standard, ensuring predictable accuracy.
Higher efficiency – engineers save time without re-typing hundreds of tolerance values.
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The Two Types of ISO 2768 Standards
ISO 2768 can be understood as two complementary standards — one controlling dimensional tolerances, the other geometric tolerances.
Type | Description | Common Codes |
ISO 2768-1 | Controls linear dimensions such as lengths, hole diameters, chamfers, and radii. | f, m, c, v |
ISO 2768-2 | Controls geometric features such as perpendicularity, parallelism, and concentricity. | H, K, L |
In short:
ISO 2768-1 ensures the size of a part is consistent.
ISO 2768-2 ensures the shape of a part is not distorted.
They can be applied separately or together on the same drawing.
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What Does “ISO 2768-mK” Mean?
The notation “ISO 2768-mK” consists of two tolerance grades, each representing a different aspect of precision.
Symbol | Reference Standard | Meaning | Controlled Feature |
m | ISO 2768-1 | Medium grade for dimensional tolerances | Length, diameter, chamfer, spacing |
K | ISO 2768-2 | Medium grade for geometrical tolerances | Flatness, perpendicularity, symmetry, concentricity |
In short:
“m” keeps parts the right size.
“K” keeps parts the right shape.
Thus, “ISO 2768-mK” indicates the drawing applies both medium dimensional and medium geometrical precision grades.If only “ISO 2768-K” is shown, it applies to geometry only;if “ISO 2768-mK-E” appears, it also includes the Envelope Condition, enforcing stricter dimensional and form control.
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ISO 2768 Tolerance Grades
ISO 2768 divides dimensional accuracy into four grades, each corresponding to a level of manufacturing precision.
Grade | Meaning | Typical Application |
f (fine) | High precision | Molds, precision parts, dowel pins |
m (medium) | General precision | Common mechanical and assembly components |
c (coarse) | Low precision | Frames, housings, welded structures |
v (very coarse) | Very low precision | Large structures, steel frameworks |
Think of it this way:
“f” is like watchmaking accuracy, while “v” is comparable to structural steelwork tolerances.
Each serves its purpose — what matters is using the level appropriate to the function.
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ISO 2768 vs. ANSI / ASME Standards
In the United States, ASME Y14.5 and ANSI B4.1 are commonly used.They serve a similar purpose but differ in application and notation.
Item | ISO 2768 | ANSI / ASME |
Regions Used | Europe, Asia, global | North America |
Classification | Linear + Geometrical combined | Usually defined separately |
Notation | Unified note on drawing (e.g., ISO 2768-mK) | Each dimension labeled individually |
Advantage | Clean drawings and consistent communication | Precise control and legal conformity |
In essence, ISO 2768 emphasizes communication efficiency, while ANSI / ASME emphasizes strict control.
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Is This Standard Really Necessary?
Absolutely.In large-scale production or cross-border projects, without a unified tolerance system, teams may face:
Misinterpretation of design intent, leading to rejected parts.
Incompatibility between components made by different suppliers.
Delays, cost overruns, and inconsistent quality.
ISO 2768 acts as a common language bridging design and manufacturing.By specifying it once, everyone involved knows the permissible deviation range for every dimension.
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Summary — ISO 2768 Is More Than Just “Error Allowance”
ISO 2768 ensures designers, manufacturers, and quality inspectors work under the same interpretation framework.
No more confusion over questions like “Is 0.1 mm acceptable?”
That’s why many global manufacturers adopt ISO 2768-mK as the baseline standard for engineering drawings.
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Why Choose Sheng Fong Precision?
With years of experience in precision manufacturing and international tolerance standards (ISO, JIS, DIN, ASME), Sheng Fong Precision helps clients apply appropriate tolerances to avoid costly rework or miscommunication.
We provide:
Expert Consultation: Assistance in determining correct tolerance grades and manufacturability.
Comprehensive Standards Coverage: Metric and imperial systems, multiple material options.
Flexible Production: From prototypes to small-lot or batch production.
Quick Lead Time: Immediate scheduling for urgent or project-based orders.
📩 Need to apply ISO 2768 to your drawings?Contact Sheng Fong Precision for professional guidance on tolerance settings and dimensional accuracy.
LINE ID: @s9000
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