The Stovebolt Site Forums The Shop Area Engine Shop Valve evaluation

I have a pile of used valves. What is the general opinion of using any in a rebuild? I have done so in the past after looking them over, but have never done much in the way of measuring anything. My evaluation consists of looking at the margin, seeing if they are straight and that the face shows no sign of being out of round or burned. I haven't had much problem with them, but what is the most correct way of doing this. I would imagine using a mic on the shaft and chucking them up in a drill press or lathe to check for being bent is a start.