Luke11CNC Build Log ,I'm so naïve

[JAZZCNC]

Useful ... yes MDF is not flat, but then again it depends what tolerances you're trying to work to.

Yep thats why I said "Job dependent"

. I guess I could just do half the bed (1000*910mm, or 2000*455 but probably the former) and leave the other half MDF.

Yes thats not a bad idea. . . I actually do put MDF full length down one side sometimes for jobs that are awkward to clamp or drilling and obviously don't need flatness.
The good thing about MDF is that it's easy to screw into and for small parts that need profiling some times it's easier because the slots don't line up and make clamping hard if not impossible. Thats why the more and closer the slots are together the better really because it gives you more % chance of always dropping on a hole or something to latch onto with clamps or bolts.

Has you probably Know full well Jonathan the bed and imparticular material clamping is an often un-thought about side of building a machine and can be a right pain in the arse. I can honestly say that yes while it was expensive other than the water cooled spindle it's the best upgrade I've made to my machine by far and wished I'd done it 2yrs sooner, makes work holding so much easier and far more accurate/repeatable.