QUOTE (aracane @ Nov 23 2009, 10:26 PM)

For wooden forms get some clear Maple. Nice and hard and holds the machned groove well. I made my roughing forms from Maple. No knots and doesn't warp.
Cheers!
Arne
Totally agree with that Arne, but I would get it as straight, tight grained, and clear of knots as possible, and then quickly seal it with a couple of coats of varnish. It's what you do with a wood door and planing forms are more critical.