= Lay parallel to view
Lay parallel to view · Estado superficial · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “Ra 1.6 with lay = in front view” states a lay parallel to view requirement.
What controls
Lay symbol requiring the machining marks to run parallel to the line representing the surface in the view where the callout appears. The reference is always that view of the drawing, not the part seen from any angle, which is where most of the confusion arises. It is a process requirement with a functional consequence: continuous lay in one direction is a preferential path for fluid and a barrier in the perpendicular direction.
How to verify
Visual check under grazing light or with a magnifier, comparing the observed orientation against the drawing view where the symbol appears. Roughness on that surface is measured with the stylus traversing perpendicular to the lay, that is, across it: measuring along the lay gives values much better than the real ones and is not valid.
Common mistakes when interpreting it
- Reading 'parallel' relative to a part axis instead of relative to the drawing view.
- Measuring roughness along the lay instead of across it.
- Doing a manual touch-up that crosses the original marks and changing the lay direction without realizing it.
How to get it in the workshop / if it comes out of tolerance
It is achieved with a machining strategy that always sweeps in the same direction: milling with parallel passes, longitudinal surface grinding or longitudinal turning on cylindrical surfaces. On a sealing face, lay parallel to the leak path encourages leakage; check the function before assuming any orientation will do. Tool entries and exits must be planned so they do not break the continuity of the marks.
If the direction does not match, change the toolpath strategy or the fixturing orientation; it is not a matter of feed or speed. If cross marks appear from a later touch-up pass, the lay is no longer the one required even though the underlying pattern is. And if the surface seals poorly while meeting Ra, check whether the lay is oriented along the leak path.
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