Hi Dave, thanks for the quick reply. I actually have two-sided lighting off all the time, so that I can ensure normals are OK. In the original maya file, normals are fine, when I export the OBJ and import it back in, then it seems to reverse some things.

I know there are a lot of n-gons. I think I got a little lazy when bevelling edges and using booleans, because I didn't see a better way to make holes in those objects and I really can't use split poly on those n-gons with the holes now.

I'm modelling a uniselector from the Colossus machine.

What shall I do with the n-gons???