√— Machining required
Machining required · Estado superficial · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
The diagonal bar on the roughness symbol means the surface must be machined; without it, it may be left as cast or forged according to the drawing.
What controls
A variant of the surface texture symbol requiring that face to be produced by material removal: it may not be delivered in the as-cast, as-forged, as-rolled or as-cut condition. It is a process requirement that also has a dimensional consequence, because it implies that the blank must have machining allowance on that face. It may be accompanied by the required roughness value and the planned machining allowance.
How to verify
Visual verification, aided by grazing light, that the whole surface shows machining marks, with no remnants of casting or mill scale skin. The finish is checked with a profilometer if the symbol gives a value. When you want to confirm how much material has been removed, compare the resulting dimension with that of the blank or measure the remaining wall thickness, which is the check that really matters on castings.
Common mistakes when interpreting it
- Taking a skim pass that only touches the high spots and considering the face machined.
- Programming without checking that the blank has allowance on that particular face.
- Confusing it with the symbol that prohibits material removal, which is exactly the opposite requirement.
How to get it in the workshop / if it comes out of tolerance
When you see it on a casting or forging drawing, check that the blank has material on that face before programming: it is the most frequent cause of parts that end up undersize. Machining means actually removing material, not taking a cleanup pass that just touches the high spots: if the surface is left with areas of original skin uncut, the face has not been machined. Also expect that machining will expose sound material that looks different from the adjacent faces.
If areas are left uncut after the pass, don't take the dimension down without first checking wall thickness and related dimensions: it may be better to reset the origin to share out the defect. If machining allowance is consistently short, the problem is in the blank and must be taken up with the foundry or forge. If porosity appears when you reach size, the allowance was not enough to get past the surface layer.
Related symbols
Other symbols in Surface texture
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