MDF or ply?

[alex wight]

I used to use a sabre 404, and the bed was aluminium slotted 200mm wide. On top of that was 5 mm sign board (foamex), and on top of that was 10mm foamex. They were bonded on with double sided carpet tape. Once the 10mm was worn, we cleaned it off by machining it of (table self cleaning option), then reapplied new 10mm foamex. Finishing with levelling the new bed. I'm ready to build a machine at the moment and looking at this way of doing it. The foamex doesn't distort like woods. I would steer clear of mdf, it has aims of its own and isn't healthy either.