6063 is "architectural grade" aluminum, which means it's for show, not strength. You can usually spot it by the bright finish. I should look it up and spout exact numbers, but it's basically half of the strength of 6061-T6, so don't use it for anywhere structural if you can help it. You can also tell 6063 when you drill it. 6063 just sort of crumbles, whereas 6061 will spiral out around the drill bit in long strands, refusing to let go...
Mark Langford, Huntsville, Alabama N56ML "at" hiwaay.net see KR2S project at http://home.hiwaay.net/~langford
