Not necessarily CMM related. Lets say I have a part with an OD with a size callout of Ø1.500 +0.001/-0.000 and the surface has a taper of about 0.002 over the length of the part. At the one end it measures 1.4997 and at the other end it measures 1.5012. How do you report the size of the dimension?
On the QC sheet I do I basically just have a box to input one number. So I can report a single number and say 'OK' or 'NOT OK'. What it usually happens is I will put one number that I think makes sense, like the largest an OD is since it might mate inside of something and then a machinist will measure the small end and say I'm wrong the part is good.
There are a lot of times things can't be reduced to a single useful number. In your example, both ends are out of tolerance. (Rule 1, aka the Envelope Principle, aka dimensions apply the full length of the feature)
Hopefully, there is a space on the form for QC comments to fully explain what's going on.
Not to muddy the water to much and not an answer to the question, surely you would expect there to be a tolerance for parallelism as well to constrain the dia within an envelope therefore highlighting an out of tolerance if tapered
In such cases, I report several diameters indicating the level at which it was measured with a comment about it, then the engineers deal with it, whether it suits them or not.
Yeah. There is no reason to overthink plenty of engineering requirements since most of those folks had only one GD&T semester as part of their BA education. People on this forum often post question before 1st consulting their own engineering staff regarding part fit form function & design engineering manufacturing & assembly processes.
Unfortunately I am the whole engineering department and qc department at my company. They hired me on 1 year out of college without anyone here to train me. Last engineer quit before I started! Basically have to do and learn everything myself. It's a small place though about 100 employees. Truly grateful for your guys help when I post stupid questions!
Well in that case discuss this with the big shots. If they are so scrooge-like by not hiring separate engineer on the site then it's their problem. 100 employees???? I once worked at a stamping shop with 30-40 employees & yet we had one QC manager, one QC engineer & one inspector. Not to mention 2 engineers.
