ISO 2768 Edition 2: What Changes for CNC Drawings in 2026

ISO 2768 Edition 2 is still at ISO Stage 60.00, International Standard under publication, as of September 5, 2026. It is expected to replace ISO 2768-1:1989, which ISO still lists as Published and Stage 90.92, To be revised. No new general tolerance values have been introduced for the retained linear and angular size tables. The main changes are scope and interpretation: Edition 2 is limited to linear and angular sizes, removes the old broken-edge tolerance limits, deletes Clause 6, and removes the former material and manufacturing-method restrictions.

For CNC drawings, the practical change is feature classification. A hole diameter can be a linear size. A hole-center location or step height is a distance, not the same type of specification. Legacy ISO 2768-mK notes also need review because the K class came from withdrawn ISO 2768-2:1989, while ISO 22081:2021 now provides the current framework for general geometrical and general size specifications.

1. ISO 2768 Edition 2 Is at Stage 60.00, Not Yet Published

The ISO project page lists ISO 2768, Edition 2, at Stage 60.00, International Standard under publication. The project entered Stage 60.00 on June 2, 2026. Stage 60.60, International Standard published, is still blank as of September 5, 2026. ISO also states that the new edition is expected to replace ISO 2768-1:1989.

The lifecycle also shows that the FDIS was registered on February 2, 2026, the formal approval ballot began on April 6, and voting closed on June 2 before the project moved into publication. Those dates show that Edition 2 has passed the approval stage, but they do not convert Stage 60.00 into publication. The status line on the ISO project page remains the publication checkpoint for this article.

That status affects controlled drawings and contracts. A design team can review title blocks now because the approved FDIS identifies the technical changes, but a released specification should not describe Edition 2 as a published International Standard until ISO records Stage 60.60. The final published designation and text should be checked again before a company drawing standard or contractual reference is revised.

ISO 2768-1:1989 remains a Published standard at Stage 90.92, To be revised. It has not yet been marked Withdrawn. Keep that distinction when you review an existing drawing. A legacy drawing that cites ISO 2768-1:1989 still has a defined historical reference; a new drawing prepared for Edition 2 needs the new scope and GPS rules described below.

2. The Tolerance Values Stay, but Their Scope Changes

No new tolerance chart is the central point. The Edition 2 FDIS Introduction states that its tolerance limits have not been updated and that the same values used in the past for general specification of linear and angular sizes are retained. For the 1989 medium class, ISO 2768-m gives ±0.2 mm over 6–30 mm and ±0.3 mm over 30–120 mm. Those figures remain legacy standard values, not EPOC CRAFTER machining capability claims.

The change is where those values apply. ISO 2768-1:1989 used the broader term linear and angular dimensions and included distances, radii, external radii, and chamfer heights within its stated scope. Edition 2 specifies a system of tolerance limits for linear and angular sizes. Its nominal linear-size range is 0.5–4,000 mm, and the Scope excludes other dimensional specifications such as linear and angular distances.

Material and manufacturing method no longer form the old boundary. The 1989 Scope centered on metal removal and sheet-metal forming, with a note about possible use for other materials. Edition 2 extends the field of application so it is independent of material and manufacturing method. That does not make one class equally capable or equally economical in every process. Machining precision, DFM limits, material grade, surface finish, fixturing, inspection method, prototype quantity, and production-run requirements remain separate engineering decisions.

Table 1: 1989 vs Edition 2 Change Matrix

Linear and angular tolerance values	Legacy class values	Retained for applicable sizes	Do not expect a new tolerance chart
Scope terminology	Linear and angular dimensions	Linear and angular sizes	Classify the characteristic before applying a general tolerance
Linear and angular distances	Included in the old broad scope	Excluded from Edition 2 size scope	Specify the required relationship separately
Broken edges	Table 2 covered broken-edge external radii and chamfer heights	Tolerance limits removed	Review edge requirements instead of carrying Table 2 forward
Clause 6	Function-based rejection rule	Deleted	Use the applicable conformity decision framework
Material and manufacturing method	Scope centered on metal removal and sheet-metal forming	Restriction removed	Do not confuse scope expansion with process capability
General geometry	Combined with Part 2 through mK-style notes on many legacy drawings	ISO 2768-2 is withdrawn; ISO 22081:2021 is current	Review the geometry portion of legacy title blocks

3. A Drawing Dimension Is Not Automatically a Size

ISO 14405-1:2025 defines linear size as a dimension in length units that characterizes a feature of size. Its principal covered features are cylinders, spheres, and two parallel opposite planes. The definition is narrower than everyday drawing language. A value written in millimetres is not automatically a linear size.

ISO 14405-2:2018 defines distance between geometrical features that are not considered together as one feature of size. Its Table 1 lists several drawing dimensions that are not sizes, including step height, feature-to-feature distance, distances involving derived features, radius, arc length, and chamfer height. This distinction explains why Edition 2 cannot be read as a blanket general tolerance for every untoleranced number on a drawing.

3.1 Hole Diameter and Hole Location Are Different Specifications

A cylindrical hole diameter is a linear size. A basic callout such as Ø20 ±0.1 is a linear-size specification. When no size modifier, drawing-specific default, or altered default changes the rule, ISO 14405-1:2025 assigns two-point size as the ISO default specification operator. The ± tolerance gives limits for that size characteristic; it does not turn unrelated location or geometry requirements into size requirements.

Move from diameter to location and the classification changes. The distance from a hole axis to an outside face involves a derived feature and an integral feature, so ISO 14405-2 treats it as a linear distance. Hole-center spacing is a distance between derived features. A drawing may show Ø20, a 35 mm axis-to-face dimension, and a 50 mm center-to-center dimension beside each other. Only the diameter belongs to the linear-size case described above.

For a deeper drawing workflow that separates default tolerances from feature-level callouts, use EPOC CRAFTER’s how to tolerance a CNC drawing guide.

3.2 Plate Thickness Can Be a Size; Step Height Is a Distance

Two parallel opposite planes can form one feature of linear size. Plate thickness, block width, or slot width can fall into this category when the opposed planes are treated together as one feature of size. ISO 14405-1 identifies two parallel opposite planes as a principal feature type and allows width or thickness as the size expression.

Step height is different. Two same-facing integral surfaces do not form the same feature-of-size case, so their separation is a linear distance under ISO 14405-2. A 10 mm plate thickness and a 10 mm machined step can look similar on a 2D drawing, yet Edition 2 does not place them in the same general-size category. The feature definition decides the rule, not the appearance of the dimension line.

3.3 Radius, Chamfer, and Angular Dimensions Need Separate Rules

ISO 14405-2 places radius, chamfer height, arc length, and several feature-to-feature dimensions among dimensions that are not sizes. A radius symbol or a ± value does not convert them into linear sizes. ISO 14405-2 also warns that ± tolerancing of non-size dimensions can create specification ambiguity on real workpieces because form and angular deviations affect how the dimension is realized. Its Scope explicitly includes general tolerances such as the legacy ISO 2768-1 context.

Angular dimensions have the same boundary. ISO 14405-3:2016 applies angular size to an angular feature of size, including cones, frustums, wedges, truncated wedges, and qualifying opposite non-parallel planes. An angle between independent surfaces is not automatically an angular size.

Table 2: Common CNC Drawing Dimensions, Size or Not?

Shaft or hole diameter	Linear size	Within linear-size scope	Apply the selected general class only when no individual size tolerance overrides it
Plate thickness between opposed parallel faces	Linear size when the faces form one feature of size	Within linear-size scope	Confirm the two faces form one feature of size
Slot width between opposed parallel faces	Linear size when the faces form one feature of size	Within linear-size scope	Confirm the feature definition
Step height between same-facing planes	Linear distance	Outside linear-size scope	Specify the intended relationship
Hole axis to outside face	Linear distance	Outside linear-size scope	Define the location requirement
Hole center to hole center	Linear distance	Outside linear-size scope	Review the location specification
Radius R	Non-size dimension under ISO 14405-2	Not a linear size	Specify the required radius control
Chamfer height	Non-size dimension	Old broken-edge Table 2 no longer supplies the Edition 2 limit	Specify the chamfer requirement if it matters
Cone or wedge angle	Angular size when ISO 14405-3 conditions are met	Can fall within angular-size scope	Confirm that the angle belongs to an angular feature of size
Angle between independent surfaces	Angular distance or another geometric relationship	Not automatically an angular size	Define the intended geometric relationship

4. Broken-Edge Tolerances Leave ISO 2768

ISO 2768-1:1989 Table 2 supplied permissible deviations for broken-edge external radii and chamfer heights. Edition 2 removes those tolerance limits. The change is a deletion, not a new replacement table inside ISO 2768.

That deletion changes how a legacy title block should be read. An untoleranced broken-edge external radius or chamfer height that previously relied on Table 2 should be reviewed before the drawing is revised for Edition 2. Do not carry the old Table 2 numbers forward by assumption.

ISO 13715:2017 handles a different specification problem: edges of undefined shape. It provides indications for permitted material excess, material removal, passing, and undercut, with both individual and general edge indications. An explicitly defined chamfer such as 1 × 45° has defined nominal geometry, so ISO 13715 does not automatically provide the dimensional tolerance for its 1 mm size or its 45° angle.

For a drawing review, separate three cases. A defined chamfer needs the specification required by its function. A defined radius needs its required geometric or dimensional control. An intentionally undefined deburred edge can use an ISO 13715 edge condition when burr, passing, or material removal needs a limit. A note such as BREAK SHARP EDGES should be checked against the intended edge condition instead of treated as a substitute for all three cases.

5. What Happens to Legacy ISO 2768-mK Drawings?

Do not label every existing mK drawing invalid. Read the drawing against its revision, contract, customer specification, and referenced standards. The migration issue is more specific: the m and K components come from different standards histories, and the geometry part no longer belongs to a current ISO 2768 Part 2 framework.

The m class comes from ISO 2768-1:1989. The K class came from ISO 2768-2:1989, which ISO now lists as Withdrawn. ISO identifies ISO 22081:2021 as the new version, and the ISO 22081 Foreword states that its first edition cancels and replaces ISO 2768-2:1989 after technical revision. ISO 22081 supplies rules for general geometrical specifications and general size specifications.

ISO 22081 does not reproduce mK as a replacement two-letter class. Its general size specifications cover linear and angular sizes, while its general geometrical specifications have their own applicability and indication rules. ISO 22081 applies these general specifications to integral features, including features of size, and excludes derived features and integral lines from that general scope. Its general-size rules further identify which features of size receive the general size specification.

ISO 8015:2011 adds the interpretation rule needed for a revised title block. General GPS specifications apply to the corresponding characteristics that have no individual specification. An individual GPS specification controls its own characteristic instead of being mechanically stacked with the general requirement. Conflicting general GPS specifications can create ambiguity, so their scopes need to be separated when more than one general system is invoked.

A revised drawing should split the old mK assumption into two questions. Which linear or angular sizes need a general ISO 2768 tolerance? Which geometric characteristics need a current general or individual geometrical specification? EPOC CRAFTER’s guide to features that need tighter CNC tolerances is useful for the second question when a bore, locating pattern, sealing face, or other functional feature needs a local callout.

6. Clause 6 Is Gone: Read Inspection Decisions Separately

ISO 2768-1:1989 Clause 6 said that a workpiece exceeding a general tolerance should not be automatically rejected when its ability to function was not impaired, unless another requirement applied. Annex A.4 explained the functional context. Edition 2 deletes Clause 6 from its normative body.

The deletion should not be rewritten into the opposite rule. Edition 2 does not say that every measured value beyond a specification limit is an automatic reject. It removes the old ISO 2768-specific rejection statement. Conformity and nonconformity decisions belong to the applicable GPS verification framework and any contractual decision rule that the parties have established.

ISO 14253-1:2017 provides the relevant GPS framework for decision rules involving specification limits and measurement uncertainty. It distinguishes the specification zone, acceptance zone, rejection zone, guard bands, and an uncertainty zone near a specification limit. For conformity verification, the measured value must fall in the applicable acceptance zone. For nonconformity verification, it must fall in the applicable rejection zone.

ISO 14253-1 uses default 95% conformance and nonconformance probability limits unless another value is agreed and documented. Under the normal probability-density conditions stated in Clauses 5.2.2 and 5.3.2, the default guard-band factor is about 1.65 times the combined standard uncertainty. That factor belongs to those stated conditions. It is not a universal shop-floor allowance that can be added to every CNC tolerance.

Supplier and customer rules in ISO 14253-1 are metrological rules, not legal burden-of-proof rules. Where no different agreement exists, the supplier verifies conformity using its estimated measurement uncertainty and the customer verifies nonconformity using its estimated measurement uncertainty. The standard does not assign contract liability, warranty responsibility, damages, or litigation burdens.

Near a limit, record the characteristic, specification limits, measurement method, applicable decision rule, and measurement uncertainty. A drawing specification defines the required characteristic; it does not automatically prescribe a CMM, micrometer, gauge, or other verification operator.

Table 3: Inspection Terms That Should Not Be Collapsed Into One Limit

Specification zone	Values that satisfy the stated specification
Acceptance zone	Region where conformity can be verified under the applicable decision rule
Rejection zone	Region where nonconformity can be verified under the applicable decision rule
Uncertainty zone	Region near a specification limit where the required conformity or nonconformity decision cannot be established at the selected probability limit

7. Audit the Drawing Before the Next RFQ

A drawing migration should end with a title-block and feature-level audit, not a global search-and-replace. Review every characteristic that depends on a general note, then check whether an individual tolerance or geometric specification already controls the same feature. This keeps quoting, machining, and inspection aligned before a prototype or production run reaches the supplier.

Table 4: ISO 2768 Edition 2 Drawing Review Checklist

ISO 2768-m	Edition 2 covers applicable linear and angular sizes, not every untoleranced dimension	Classify each dependent characteristic before applying the general class
ISO 2768-mK	K belongs to withdrawn ISO 2768-2:1989	Separate general size and geometry requirements
Untoleranced step height	Step height is a linear distance	Specify the intended relationship
Hole-center spacing	Distance between derived features	Use the intended location specification
Untoleranced chamfer	Old broken-edge Table 2 is removed	Add the dimensional or geometric requirement needed by function
BREAK SHARP EDGES	Defined chamfer, defined radius, and undefined edge are different cases	State the intended edge condition
General geometry note	ISO 22081:2021 is the current replacement route for old Part 2 general geometry	Confirm applicable characteristics and datum needs
Feature with an individual tolerance	Individual specification controls that characteristic	Keep the local requirement and do not duplicate it through a general note
Inspection result near a limit	Measured value alone does not describe the full decision rule	Check measurement uncertainty and the agreed or default conformity rule
Copied legacy title block	It may combine standards with different current statuses	Verify every referenced standard before release

Use three checks for each Edition 2 migration review. Ask whether the characteristic is a true linear or angular size. Check whether an individual specification already controls it. For inspected features near a limit, confirm which conformity rule and measurement uncertainty apply. The drawing should also separate standard interpretation from manufacturing capability. A general tolerance class does not state the achievable precision of a specific CNC process, material grade, fixture, or inspection setup. Use EPOC CRAFTER’s DFM design guidelines when manufacturability is still being resolved, and use our CNC machining capabilities page when the drawing is ready for an RFQ. Keep function-driven feature tolerances explicit before the file is released