Ⓢ Regardless of Feature Size (RFS)
Regardless of Feature Size (RFS) · Modificadores de zona · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “⌖ ⌀ 0.05 |A|B|C| (no material condition modifier)” states a regardless of feature size (rfs) requirement with a cylindrical tolerance zone of ⌀ 0.05 mm, measured from datums A, B, C in that order of precedence.
What controls
Indicates that the geometric tolerance applies in full and without variation, whatever the actual size of the feature: there is no bonus. In ASME Y14.5 it is the default condition when the frame carries neither Ⓜ nor Ⓛ, and the Ⓢ symbol was dropped as unnecessary. In ISO 1101 the default interpretation is also regardless of feature size, and material-condition behavior is requested explicitly with Ⓜ or Ⓛ. It is the most restrictive criterion: the same part that would pass with Ⓜ may be rejected here.
How to verify
The zone to verify is fixed, so the measurement does not depend on size: the actual geometric deviation of the feature relative to the datum reference frame is measured and compared directly with the frame value. On a CMM, make sure the evaluation is NOT in material-condition mode: if the software applies bonus by mistake, it accepts parts that should be rejected. Go/no-go functional gauges do not work here, because they have the bonus built in by design; actual measurements are needed, normally by CMM or by mounting the part between centers with a dial indicator.
Datums and notes
When the datum is a feature of size and is referenced without a modifier, it is also taken regardless of feature size: the fixture must center on the actual feature (expanding arbor, collet or self-centering vise) instead of a fixed gauge that would leave play.
Workshop guideline values
- General
- 0.1–0.3 mm on positions without a material condition modifier in ordinary machining.
- Accuracy
- 0.03–0.08 mm on dowel pin or bearing bores.
- High precision
- 0.005–0.02 mm on precision features where centering is functional and no play is allowed.
Guidance only: the drawing's value always wins.
Common mistakes when interpreting it
- Looking for the Ⓢ symbol on the drawing to know there is no bonus: it was removed from ASME Y14.5, and the absence of a modifier already means regardless of feature size.
- Leaving bonus evaluation enabled on the CMM for a frame without a modifier: it accepts parts that should be rejected.
- Asking for a functional gauge to verify a frame without a modifier: that gauge has the bonus built in by design and does not reproduce the criterion.
How to get it in the workshop / if it comes out of tolerance
In ASME it is the default if there is no Ⓜ or Ⓛ. In ISO it may be indicated explicitly. More conservative for inspection.
With no bonus, the margin has to come from the process: spot drilling first, work offset correction, wear compensation and thermal control. Work with short, rigid tooling and check centering before the critical pass. If the drawing calls for a control without a modifier on a simple clearance hole, it is worth asking engineering whether Ⓜ would be functionally acceptable: it usually makes the part cheaper without affecting assembly.
Alternative symbol:(ninguno)
Other symbols in Zone modifiers
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