Engine Turning

I spent some time searching VAF archives to find a picture of polished aluminum part and related topic. Was it a baffle, a tool or something else I do not remember. But it looked like Joe Condon's firewall here (post #8) http://www.vansairforce.com/community/showthread.php?t=27199&highlight=firewall+polishing but it was aluminum.
Does somebody remember? I tried many related search words, turned empty.

It's called "engine turning". A couple of posts there told how they had done it.