I am using a circle as a datum to a hole pattern of .014TP. My question is in measuring of the circle for the datum I have an Err of .0118 how does this factor into my locations of the measured hole features?
It will likely affect the size/location results for your datum feature first. Size is important if your datum has a MMB/LMB modifier. Location is important because it will affect your alignment.
Are you allowed to restrain the part, or do the dimensions apply in a free state? Most of my parts have a note saying that dimensions apply when datum features are restrained, but I never get fixtures to restrain them at inspection. In that case, I measure my datum with the least squares algorithm and report as normal, trying to be aware of how my part deviates from perfect form in the free state. If you are not allowed to restrain the part, then I would use a max-inscribed or min-circumscribed algorithm for the datum feature.
It will likely affect the size/location results for your datum feature first. Size is important if your datum has a MMB/LMB modifier. Location is important because it will affect your alignment.
Are you allowed to restrain the part, or do the dimensions apply in a free state? Most of my parts have a note saying that dimensions apply when datum features are restrained, but I never get fixtures to restrain them at inspection. In that case, I measure my datum with the least squares algorithm and report as normal, trying to be aware of how my part deviates from perfect form in the free state. If you are not allowed to restrain the part, then I would use a max-inscribed or min-circumscribed algorithm for the datum feature.
