Quote Originally Posted by Bruce View Post
Rather than getting all wadded up about the Norton not being flat, have you tested the edge of your Shapton to determine if it is straight? The results of that additional testing might be illuminating.
I tried it against several things, including a borrowed straightedge from my building's maintenance man. Yes, it's bowed. I used the Shapton in the photo because I know it's straight, and it was the easiest thing at hand for the purpose.