True position of a hole is to datum A, a cast face we are not allowed to machine. The face is lumpy by 0.3 mm. The hole itself is round and where the fixture put it. The CMM fails position.
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If A is an unmachined cast face, the position tolerance has to be large enough for that face or the face has to be a machined datum. A perfect hole to a lumpy datum fails honestly. Do not bend the program to chase the lump.
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Ask the buyer whether A was meant to be the machined pad next to it. Datums get copied onto cast faces by mistake. A revised datum saves the part. A tighter hole does not.
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Questions and answers were written on this account when they were published.
Report the hole location to the machined features as extra information, and the position to A as the drawing asks. Both numbers, labeled, beat one flattering number.
Forum posts from Zoryra Forum.
Questions and answers were written on this account when they were published.
