Wouldn’t it be amazing if there was a product that could be mixed up and poured on an existing waste board and then be milled flat?
I was thinking epoxy, but I suspect that running hold down screws through it would cause it to break away.
Anybody else entertain this idea?!
Fiberglass maybe?
You don’t want to flinging that much tiny glass everywhere - it’s really not good for your lungs.
You could just use one of the pourable countertop resins. It would be expensive and would need well supported to be stable but would work. It’ll still be messy.
What you need to do is figure out a power float attachment for your router and make a polished cement table! Could be hard on your bits though 
Some sort of foaming resin might be perfect. Hard enough to hold a screw. Easy to mill flat.
Cool idea
Brb, just Amazon’ing 5 gallons of gorilla glue…
Plaster of Paris? Easy to mix, won’t kill your tools.
Even ready mixed plaster -schmear on a layer, let it dry and surface it.
hmm…..
Haven’t tried pouring to redo those oops moments. But I do play with making inlays. I just cut a few 5 x6 1/4 thick. When the board gets ratty,mill out a pocket and glue in new piece. You can tell the first few tries from the new ones 
In order for this to work, you need a high level of precession in your existing build. The table needs to be level beyond what you could get from a bubble level, and your CNC framework must place your router plane absolutely parallel with the table. While not impossible, it is probably simpler to just surface the spoil board.
One of my routers doesn’t mind if the spoilboard isint flat. I get all my v-bits routing work using my floating z attachment (i just loosen up 1 screw at the top of the z azis)
Here is a bad quality picture of the z azis plus the auto depth regulator (from a video Tuesday can get a good quality picture of it)
But this wont work on a lowrider
Are you looking to level a fresh new spoilboard, or, rejuvenate a well used one? If rejuvenating, and already flipped and throughly used the other side, then…
I thought about skim coating with something cheap like drywall top coat before, but that won’t help with holding down screws, and the dust management will be annoying.
Maybe recycle chips collected in dust stopper separated bucket, mix with cheap wood glue, fill and skim coat. Won’t be able to reproduce the pressure applied during original manufacturing of spoilboard. But, maybe the rough surface will be good enough since it’ll be resurfaced before doing cuts/carves? Guessing replacement is less time/hassle overall for smaller builds.
I would suggest cheapo’ wood glue
No matter what, i would suggest: seal everything made of wood, including the wasteboard. And reapply evrey now and then (even if not resurfacing) mdf will absorb humidity
Well, i was thinking Self Leveling Cement, til you mentioned the milling 
He could pour liquid acrylic or 2part nail 
resin. That should be very forgiving with the cnc bits.
Honestly i cant see a reason to do that, my last spoilboard lasted almost a year. Many surfacing paths and manual sanding later. Some toe clamps to be highly considered as an option. I do use tham (3d printed)
Plane the old waste board, glue a new one on top? 
I have been saving all my reject pla prints to remelt into something….
I did this not too long ago. Melted into a flat sheet pan, then surfaced on the LR4 and cut some coasters out of them. I use them around the shop. Have a ton more PLA saved up to do again one day when time allows.
I’m not familiar with foaming resin. I looked it up and it seems like this might have potential. Have you used it before?
I filled the sides of the boat I made with it - that’s about my only input
It is big in the jetski world, I know you can get varying densities as well. Cool stuff.
Have fun milling it. You’ll need a box of trash bags to empty the fluff into. 
