Ⓒ Continuous feature
Continuous feature · Modificadores de zona · ASME Y14.5
Example in plan
How to interpret it
On the drawing, “⏥ 0.05 Ⓒ |A| on two collinear faces” states a continuous feature requirement with a tolerance of 0.05 mm, measured from datum A.
What controls
Indicates that two or more segments shown as separate on the drawing (a bore interrupted by a groove or an undercut, two aligned mounting pads on a cover, two coplanar faces with a recess between them) are to be treated as a single feature for size and geometry purposes. Without Ⓒ, each segment is an independent feature and each conforms on its own: two bore segments can both be within size and misaligned with each other, and the part would still pass. With Ⓒ, the whole set is evaluated as if the material between them did not exist, so the envelope or common axis runs through all the segments. What it does NOT do is create a pattern or require machining in any particular way: it only changes how the measured data are grouped.
How to verify
The natural physical check is a gauge or arbor that passes through all segments at once: if it goes all the way through, the continuous feature conforms at its envelope. On a CMM you have to probe the segments and combine them into a single feature before evaluating (one cylinder with points from both sides, one plane with points from both faces), rather than computing two features and comparing their results: the latter is exactly the opposite of what Ⓒ requires. Distribute the points evenly between segments; if one contributes many more points than the other, the fit is biased towards it.
Common mistakes when interpreting it
- Checking each segment separately and passing the part: with Ⓒ what counts is the whole, not each half.
- Confusing it with a pattern of repeated features: here there are not several features with their own zones, there is just one feature drawn in pieces.
- Assuming that without Ⓒ the segments are already evaluated together because they are aligned on the drawing: if it is not indicated, each segment is an independent feature.
How to get it in the workshop / if it comes out of tolerance
The shop-floor message is straightforward: machine all the segments in the same pass and in the same setup whenever you can. An interrupted bore with Ⓒ has to be drilled or bored in one go, because if it is done from both sides and a step is left, the continuous feature fails even though each half is perfect. The same goes for coplanar pads: a single facing pass that sweeps both of them, or re-level the whole set before the second one.
If it fails, suspect number one is a step between segments caused by a change of setup or tool: machine in one pass, or at least with the same tool and without unclamping the part. In long interrupted bores, check for drill walk and use a guide bushing or a through finish-boring pass. On coplanar faces, watch for part deflection from clamping, because each area deflects in a different direction and the set ends up in a V. If the design forces machining in two setups, leave stock and take a common final pass.
Related symbols
Other symbols in Zone modifiers
Related tools
ISO fits
Calculates indicative ISO 286 tolerances for shaft and hole, H7/g6, H7/h6, H7/k6 and H7/p6 fits with clearance, transition and interference graph.
Inspection Plans
Upload a plan, extract dimensions and GD&T with AI and export your inspection guideline in PDF or CSV.
Shop trigonometry
Workshop trigonometry: right triangle, C chamfer, Z countersink, sine bar, taper and polar→X/Y for CNC operators.