Quote Originally Posted by FrankV View Post
Ok, so this is the confusion. What do you mean by 3mm walls? If you mean the wall is 1.5mm then it would be 3mm total, but if the wall thickness is 3mm then the outside diameter must be the inside (74mm) plus the 2 x 3mm = 80mm outside dia for the lid (plus a bit of clearance of course).
GAH.

I had a funny feeling that the answer would be that I'm an idiot...

You're correct, I only accounted for 3mm of wall, not 6mm.

At least I know my printer's working correctly.

Thanks!