Originally Posted by spalm MDF will grow in thickness when it absorbs moisture and not return to its original size. |
Smaller pieces will shrink and expand. I used a 3/8" wide strip for a runner in a table saw cutoff sled. I CNC'd the panel square and with a dado to accept the MDF runner. At the most humid time of the summer, it's too tight to slide. And in the winter, it's very sloppy, so it does shrink back.
If you actually get it wet, however, it will not shrink back at all.
The biggest problem with using MDF for the frame is keeping it flat while you glue up the panels. But once you get it glued up, you shloudn't have any problems at all.
Originally Posted by spalm Plywood is the most stable of these three. Every other layer has the grain running in the opposite direction. It does not change in size (for all practical purposes). |
Actually, MDF is more stable than plywood. A sheet of MDF, lying flat, will stay flat. A sheet of plywood will amost always warp. With the exception of Baltic Birch. I cut parts for my router out of Baltic Birch, and they stayed flat for almost 2 years before I got around to assembling it.