I just finished a router jig a few days ago for various purposes. Two members are 30" long by 3" wide of 5/8" MDF. After getting the very straight pieces cut and glued, I just made one more little step. I soaked (well MDF won't really soak) one edge with shellac. Before I had gone far, I noticed the warping starting. I thought, "dummy, one edge only?". So I shellaced the other edge. That didn't cure the problem(s). Glued pieces were way out of square and both members with the shellac were very curved. They have stayed that way, though come back some after three days. And the glued angle changed too. I'm off about 1/32" plus over 30" which is unacceptable for my needs.
Should I just leave alone edges with MDF? I wanted to toughen them a little as they will guide the router base. Now I start over. But I don't want to make the same mistake again. Or should I build this thing with plywood as Bill Hylton did? I chose MDF for the smoother surface, but...
David