Hi Brad,
I cannot say that the customer was correct but that was their response to us. At the time we had thought it was typo error on the print, and had made the part at what we thought was nominal. Their response was that the part was oversized due to the minus minus dimension. If I recall correctly he said that theses tolerance were not used too often in the USA, and it was a really old print. He did give me a reference to look it up at that time but we did not have the ref book to do this, so we just remade their parts to their interpretation.
So to answer your question Brad, no I am not sure, and in my 12 years of inspection I have only seen that call out twice with that same company. As mention the customer was the National Institute for Standards and Technology (NIST), yes I do believe that any company can be wrong, but they were adamant that the minus minus was not a typo. Although if anyone has a better understanding of these tolerance’s, I am all ears. Happy days to all.
Brad
