seth
Aluminum
- Joined
- Feb 3, 2007
- Location
- Scotts Valley, Ca.
Hoping you metrology gurus can shed some light on this. I am a machinist and understand the methodology of min/max but wondering how most inspectors decide when to use this. I’ve done “some” research and honestly it’s all over the board when to use least squared and min/max. Knowing that when you have a tighter tolerance, say +/.0005, the OE is wanting a precision fit whether it be an o ring shaft etc. Functionally I understand on a bore, that a shaft or o ring seal must fit in a bore within the low of the tolerance of that bore roundness taking into account. That being said, when making a part, we do not have a cmm to verify on the floor as we make the parts and use bore gages to monitor through the run. Where the problem rises is we check at the machine in basically a restrained condition(on lathe in chuck) and get the bore to be on size. When it is released we get an out of round condition of roughly .0005. Now when inspection gets it, it will be rejected with max inscribed method and pass with least squared (average) if made to nominal. Is there a general rule when you make components where you don’t know the application and choose between these two methods. We are trying to get a standard on this as we all need to be on the same page. It really doesn’t matter to me or the other machinists which way we choose, but am hoping you guys can help with this. Side note, we don’t always know how the customer will check.
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