g Degree of machining g (as cast)
Degree of machining g (as cast) · Fundición (ISO 10135) · ISO 1101
Example in plan
How to interpret it
On the drawing, “Grade g on non-functional surfaces” states a degree of machining g (as cast) requirement.
What controls
Degree of machining stating that the surface is delivered as it comes out of the mold, with no material removal beyond dressing flash and gate marks. All dimensions in that area are governed by the general casting tolerance on the drawing, and the surface finish is the one inherent to the process. It is a statement of machining scope, not permission for the surface to come out any old way: the part must still meet the general tolerance, wall thickness and freedom from defects.
How to verify
Dimensional check against the general casting tolerance grade stated on the drawing, using calipers, templates or comparison with the model by 3D scanning. Surface finish is assessed against cast surface comparator standards rather than with a profilometer, because sand texture is not a profile the profilometer interprets well. Visual inspection also looks for flash, adhered sand, slag inclusions and core marks, which are grounds for rejection.
Common mistakes when interpreting it
- Reading “as cast” as “no requirements”: the general casting tolerance and defect limits still apply.
- Using a grade g face as a datum or as a precision fixturing locator.
- Measuring its roughness with a profilometer and comparing it with machined surface values.
How to get it in the workshop / if it comes out of tolerance
These faces have no machining allowance, so they cannot be used as precision locators, nor can you expect machined flatness from them. If the assembly needs a local seat in a grade g area, the drawing will normally call for a locally machined flat spot there. When fixturing, locate on defined points rather than on a continuous as-cast surface: no two as-cast parts sit the same way.
If an as-cast face does not fit the assembly, the solution is not to sand it: first check whether the part is within the general tolerance and whether the problem is mismatch between mold halves. If the project needs more accuracy on that face, the change belongs on the drawing (make it a machined face with its allowance), not on the shop floor. If there is embedded sand, shot blasting or grit blasting is the way; removing it with a grinder usually leaves a gouge that does end up out of tolerance.
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