R Lay radial
Lay radial · Estado superficial · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “Ra 3.2 R on flange face” states a lay radial requirement.
What controls
Lay symbol requiring the marks to be oriented radially, running from the center of the surface outward like the spokes of a wheel. It is the pattern left by certain milling or scraping operations from the center, and functionally it is the opposite of circular: radial marks cross any potential contact rings, which on a flat seal creates leak paths from the inside to the outside.
How to verify
Visual inspection under grazing light, checking that the marks converge toward the indicated center. Roughness is measured with the stylus traversing circumferentially, which is perpendicular to the lay in this pattern. Since the finish can vary between the center and the edge, measure at different radii and take the worst case.
Common mistakes when interpreting it
- Leaving radial marks on a sealing face without considering that they connect the inside with the outside.
- Measuring roughness radially, i.e. along the lay.
- Confusing the radial symbol with the circular one, which describe opposite patterns with opposite effects on seals.
How to get it in the workshop / if it comes out of tolerance
Be careful with this pattern on gasketed flange faces: continuous radial marks connect the inside with the outside and can make the joint leak despite meeting the roughness requirement. If the drawing calls for it, there will be a specific functional reason (drainage, venting, controlled contact); if it does not and the face has to seal, it is best avoided. It is generated by machining strategies that feed from the center outward.
If the seal leaks on a face with radial marks, the problem may be the pattern rather than the roughness value: consider changing the strategy to a circular or finer finish. If the pattern comes out irregular, check the toolpath and the stepover between passes. A later circular touch-up changes the required lay.
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