Key Takeaways
Quick answer: ISO 2768-mK combines the medium class m for linear and angular dimensions (Part 1) with class K for form and position tolerances (Part 2).
Status: ISO 2768-1:1989 is still valid, with a revised edition under publication for October 2026; ISO 2768-2:1989 was withdrawn on 4 February 2021 and replaced by ISO 22081:2021 (DIN EN ISO 22081:2022-10 in Germany).
Cost lever: Tighter classes mean slower machining and more inspection, so apply general tolerances broadly and tighten only functional surfaces via ISO 286 fits or explicit tolerances.
Solution hint: MakerVerse manufacturing partners work to ISO 2768 and ISO 286, and a STEP file plus drawing gets you a binding instant quote with DFM feedback on request.
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What ISO 2768 Covers, and What the Note in Your Title Block Means
ISO 2768 defines general tolerances: the permissible deviations that apply to every dimension and feature on a drawing that has no individual tolerance indicated. The designer states the standard and the tolerance classes once, in or near the title block, saving the effort of writing a tolerance next to each of dozens of dimensions. Every untoleranced dimension on that drawing then inherits its limit from the class tables.
The note has a precise anatomy:
- A lowercase letter (f, m, c or v) selects the Part 1 class for linear and angular dimensions; an uppercase letter (H, K or L) selects the Part 2 class for form and position. ISO 2768-mK therefore means class m for lengths and angles plus class K for form and position.
- An ISO 2768-m note covers Part 1 only.
- The suffix E, as in ISO 2768-mK-E, applies the envelope requirement to all single features of size, such as holes and shafts.
Scope and exclusions at a glance:
- Part 1 was written for metal-removal machining and sheet-metal forming; Part 2 mainly for machined features. Other processes are not excluded outright: before applying the note, check that the accuracy the process usually delivers stays inside the tabulated values. Cast parts follow their own standard, ISO 8062.
- Part 1 excludes auxiliary dimensions in brackets, theoretically exact dimensions shown in frames, and nominal sizes below 0.5 mm, which always carry their tolerance directly at the dimension.
- Part 2 specifies no general tolerances for cylindricity, profile of a line or surface, angularity, position, coaxiality or total run-out.
- Exceeding a general tolerance is not, on its own, grounds for rejecting the part: unless the parties agree otherwise, what decides is whether the function is impaired. If every deviation is to count as grounds for rejection, that must be written into the agreement. This rejection rule comes from ISO 2768-1:1989; the revision announced for October 2026 removes it.
ISO 2768-1 Tolerance Tables (f / m / c / v)
Part 1 of the standard defines four tolerance classes: f (fine), m (medium), c (coarse) and v (very coarse). They are intended to reflect customary workshop accuracy. The tables below reproduce the permissible deviations in millimetres for the four groups of dimensions Part 1 covers.
Linear Dimensions (Except Broken Edges)
This table applies to external, internal, step and distance dimensions, as well as diameters and radii. The nominal size is the dimension itself.
Worked example: under ISO 2768-m, a 25 mm length may measure anywhere between 24.8 and 25.2 mm, because 25 mm falls into the 6 to 30 mm range with a ±0.2 mm deviation. Below 0.5 mm nominal size the tables do not apply: the tolerance belongs on the dimension itself.
Broken Edges, External Radii and Chamfer Heights
For broken edges, the nominal size is the radius or the chamfer height, and classes f and m share one set of values, as do c and v.
Note: the revised ISO 2768 announced for October 2026 removes this table. Broken edges, radii and chamfer heights will then need an individual tolerance indication.
Angular Dimensions
For angles, the tolerance depends on the length of the shorter side of the angle; the angle value itself is irrelevant.
An undimensioned right angle takes its limit from this table. Where the drawing also invokes Part 2, the perpendicularity tolerance governs such angles instead.
ISO 2768-2 Classes H, K and L, and Why the Standard Was Withdrawn
Part 2 of ISO 2768 covers general tolerances for form and position in three classes: H (fine), K (medium) and L (coarse). It addresses straightness and flatness, perpendicularity, symmetry and run-out. The tables below reproduce the values of the withdrawn ISO 2768-2:1989, which remain relevant because a great many existing drawings still reference them.
Two characteristics are derived rather than tabulated: circularity equals the diameter tolerance but is capped at the run-out tolerance, and parallelism equals the size tolerance or the straightness or flatness tolerance, whichever is greater.
The Status Change: ISO 22081 Replaces Part 2
ISO withdrew ISO 2768-2:1989 on 4 February 2021. Its successor is ISO 22081:2021, published in Germany as DIN EN ISO 22081:2022-10, which in turn replaced DIN ISO 2768-2:1991-04. It does not continue the H, K and L classes: the general geometrical specification becomes a surface profile tolerance referenced to a datum system, and the standard itself carries no tolerance values. The value tables used in Germany come from the supplementary DIN 2769:2023-04.
A second status change concerns Part 1: a revised ISO 2768 has been at the publication stage since June 2026, with publication announced for October 2026, and will replace ISO 2768-1:1989. The new edition keeps the four tolerance classes for linear and angular sizes, but the draft’s foreword lists substantive changes: the rejection rule (Clause 6) is removed, the scope is restricted to linear and angular sizes in the sense of ISO 14405, so step and distance dimensions drop out, the table for broken edges, radii and chamfer heights is deleted, and the field of application is extended to parts independent of material and manufacturing method. Until it takes effect, the Part 1 tables above remain the reference.
What does this mean for your drawings? A standard binds only the parties who reference it, and even a withdrawn edition remains a valid choice by agreement:
- Existing drawings referencing ISO 2768-mK remain workable. What to watch is the undated reference. For Part 2, the parties can read it differently: one side applies the withdrawn 1989 edition, the other argues the reference now points to ISO 22081, and that disagreement can turn into a dispute over which edition governs the order. A similar question builds up for Part 1, because the revised ISO 2768 keeps most tolerance values but narrows its scope, so an undated ISO 2768-m can be read against either edition. The protection is the same for both parts: write the year into the reference, e.g. ISO 2768-2:1989, and state on orders which edition applies.
- For new drawings, follow ISO 22081 or state the edition explicitly.
How to Specify the Note on Your Drawing (Worked Example)
The note belongs in or near the title block, in the format ISO 2768-«class», e.g. ISO 2768-mK, ISO 2768-fH or ISO 2768-cL, with the E suffix added when the envelope requirement should apply. The rule of precedence is simple: an individually indicated tolerance always overrides the general class.
Consider a CNC-machined aluminium bracket with a 25 mm overall length, a Ø12 mm bore and a 2 mm chamfer. With ISO 2768-mK in the title block, the overall length may deviate by ±0.2 mm and the chamfer by ±0.2 mm, both inherited from the general note. The bore, however, is a functional fit, so it gets its own tolerance, for example Ø12 H7 per the ISO 286 limit system, written directly at the dimension.
Under the revised ISO 2768 announced for October 2026, chamfer heights are no longer covered by the general tolerance and would need an individual indication.
Three mistakes show up again and again in practice:
- Mixing conventions, for example writing ISO 2768-mk with a lowercase k: the Part 2 class is always uppercase.
- Applying the general note to theoretically exact dimensions in frames, which Part 1 excludes.
- Forgetting to state the edition on orders, which matters now that Part 2 has been withdrawn.
Start Your Manufacturing Project in Seconds
Skip the wait and traditional RFQ processes. Upload your file to MakerVerse to instantly access a fully vetted industrial supply chain.
✓ Instant Quotes: AI-powered pricing and DFM checks in seconds.
✓ All Technologies: CNC, 3D Printing, Injection Molding & more.
✓ End-to-End Fulfilment: From initial prototypes to full-scale production.
When General Tolerances Are Not Enough: ISO 286, Explicit Tolerances and GD&T
General tolerances reflect customary workshop accuracy. They are not a fit guarantee. When two parts must move against each other or seat a bearing, the general class is the wrong tool, and the requirement drives the specification. In assemblies there is a second trap: every part can be within its general tolerance and the stack still fails to fit, which is why tolerance stack-up deserves its own analysis instead of reliance on the general note.
When a requirement goes beyond the general class, the right tool depends on what the function demands:
- Functional fits such as bearing seats, shafts and holes belong in the ISO 286 limit system, with tolerance classes like H7/g6 defining both the tolerance and the fit type. For context, standard CNC machining at MakerVerse works to ISO 2768-m, increased precision reaches ±0.05 mm, and fits and functional features are held to Ø 0.013 mm on request.
- Form, orientation and location requirements call for geometrical tolerancing per ISO 1101, within the ISO 22081 framework for general geometrical specifications.
- Surface roughness is not covered by either part of ISO 2768: Ra or Rz values are specified per surface, and the right callout depends on the surface finish and its tolerance implications.
The decision logic is requirement first, process second: tighten only where function demands it, and let the general tolerance class carry everything else. That keeps the drawing unambiguous for the manufacturer and the inspection plan focused on the features that actually matter.
How the Tolerance Class Affects Cost and Lead Time
The class you choose is a cost and risk decision. A tighter class means slower machining, additional setups and more inspection, because more features must be verified against tighter limits. A coarser class lets the workshop work at its customary accuracy.
The DFM principle from machining practice applies: tolerances as tight as necessary, as loose as possible, because every tighter tolerance adds cost and lead time. The cheapest part is the one that does not need rework, and DFM feedback before production starts is the highest-ROI step in the prototyping cycle.
There is a quoting angle too:
- A drawing with ISO 2768-m in the title block plus a handful of functional tight tolerances quotes and machines predictably: the manufacturer knows exactly which surfaces carry real requirements and which fall under customary accuracy.
- A drawing where every dimension carries a tight tolerance, by contrast, forces effort onto features that never needed it.
What This Means When Ordering from MakerVerse
MakerVerse is a platform for sourcing industrial parts, from prototypes to series production. Upload a STEP file together with your technical drawing, and the AI-powered instant quoting extracts tolerances automatically. You receive a binding quote with a fixed price and delivery date in minutes, and CNC-machined parts ship from 5 working days.
- All manufacturing partners in the vetted supply chain are ISO 9001-certified and work to ISO 2768 and ISO 286. Standard tolerances follow ISO 2768-m, so a drawing carrying the m or mK note lands exactly on the values this guide reproduces.
- Quality control runs on Zeiss, Keyence and Mitutoyo measuring equipment, and CMM reports and FAIR (First Article Inspection) documentation are available on request.
- If the instant quote does not fit your expectations, the Manual Review option puts a manufacturing engineer on the case within 24 hours, including DFM feedback on your design.
- MakerVerse itself is ISO 27001-certified, and signing an NDA is standard practice, so your CAD files and drawings are handled with the confidentiality you would expect from a long-term supplier.
FAQ
What does ISO 2768-mK mean on a drawing?
The lowercase m is the Part 1 class for linear and angular dimensions (medium), and the uppercase K is the Part 2 class for form and position tolerances. Together they set the general tolerances for every dimension and feature without an individual tolerance. The suffix E, as in ISO 2768-mK-E, additionally applies the envelope requirement to all single features of size.
Is ISO 2768 still valid?
Partly. ISO 2768-1:1989, which covers linear and angular dimensions, remains valid, but a revised ISO 2768 announced for October 2026 is under publication and will replace it. ISO 2768-2:1989, which covers form and position, was withdrawn by ISO on 4 February 2021 and replaced by ISO 22081:2021, published in Germany as DIN EN ISO 22081:2022-10. Existing drawings referencing ISO 2768-2 remain workable when the parties agree on the withdrawn edition, ideally stated with the year.
What is the difference between ISO 2768 f and m?
Both are Part 1 classes for linear and angular dimensions: f is fine, m is medium. The difference is the permissible deviation per nominal size range. For a dimension between 30 and 120 mm, class f allows ±0.15 mm while class m allows ±0.3 mm. Class f therefore demands tighter control, which typically costs more to machine and inspect.
Does ISO 2768 apply to sheet metal and plastic parts?
Part 1 was written for metal-removal machining and sheet-metal forming. Other processes, plastics included, are not automatically covered: first check that the accuracy the process usually delivers stays inside the general tolerance values, then apply the note. Cast parts follow their own standard, ISO 8062.
ISO 2768 vs. ISO 286: which do I use?
They complement each other. ISO 2768 sets general tolerances for dimensions and features without individual indications, reflecting customary workshop accuracy. ISO 286 is the limit-and-fit system for functional fits, with tolerance classes like H7/g6 defining both the tolerance and the fit type. Use ISO 2768 for the general note and ISO 286 where a real fit requirement exists.
