√○ Material removal prohibited
Material removal prohibited · Estado superficial · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “√ symbol with circle (not machined)” states a material removal prohibited requirement.
What controls
Callout indicating that no material may be removed from that surface by any operation: no machining, no grinding, no sanding, no manual touch-up. It is usually applied where the original surface layer has a function (casting skin, mill scale, coating, treated surface) or where removing material would compromise the load-bearing thickness. It is an absolute requirement on the process, more restrictive than simply not machining: it also prohibits the touch-ups the shop usually considers harmless.
How to verify
Visual inspection under grazing light looking for tool marks, polished areas or local recesses that give away a touch-up. When material removal is suspected, the thickness or dimension is compared with the expected as-supplied value, using calipers, an ultrasonic thickness gauge or a 3D scan against the model. On coated or treated surfaces, the check may include coating thickness with a dedicated gauge.
Common mistakes when interpreting it
- Assuming that light sanding or grinding does not count as removing material.
- Confusing it with the symbol that requires machining, which is the opposite requirement.
- Leaving clamping marks on that face and touching them up afterward to hide them.
How to get it in the workshop / if it comes out of tolerance
This symbol forces you to plan workholding and handling: if no material can be removed, neither can dings, handling burrs or vise jaw marks on that face be corrected. Protect the area with soft jaws or pads and avoid resting it directly on hard surfaces. If the next operation produces spatter or overspray onto that face, set up protection beforehand, because cleaning it afterward may mean removing material.
If the surface arrives damaged, do not touch it up: report it and decide with engineering, because the options may be to accept the damage or reject the part, but not to remove material. If the requirement makes workholding impossible, rethink the fixturing or the sequence of operations. And if the note conflicts with another callout on the drawing that requires machining that area, it is a contradiction that must be clarified before touching the part.
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