Useful ... yes MDF is not flat, but then again it depends what tolerances you're trying to work to. That resin impregnated sheet sounds worth looking in to.

For me to cover my bed with 1.5x0.75" and 8mm slots would cost £475 even taking into account the 7.5% discount they give you for spending too much! Not really happening, though it would be a big advantage I can't really justify spending what my lathe cost on the router bed, could get a 60W laser and power supply for that :naughty:. I guess I could just do half the bed (1000*910mm, or 2000*455 but probably the former) and leave the other half MDF. As long as I skim them both equally that won't loose much, except it means I'll start using one end of the X-ballscrews much more than the other but that's not the end of the world. Would put a sheet of 3mm aluminium underneath half the bed to act as a coolant tray.... got a spare coolant pump.

Anyway, I'm going a bit off topic there. I've put the slot in the mount as requested and the Z-axis is very close. Done a little wiring on the control box too.