[Flaschard]

How about this for a spoilboard idea: (Apologies if this is old news.)

Cut strips of 18mm MDF (or whatever you use) to size to fit the vacuum table/gaps between T slots.
Seal edges.
Construction glue the strips to the machine base/vacuum table.
Skim all surfaces.

There you have it! A completely vacuum sealed spoil board - with full access to the T slots and that isnt' going to warp/bend/lift up etc.

I will use this as normal until multiple skimmings leave about 10mm left, then just glue new 18mm sheets on top. This process can be repeated ad infinitum - when your skimming reaches the glue layer just glue fresh 18mm strips, skim, and carry on.

[CitizenOfDreams]

What's the purpose of the glue? Why not just lay the spoilboard on the table, put the part on top and turn the vacuum on, like everyone else does?

[Flaschard]

Well I don't know about you but my spoil board drives me nuts!

Put down a fresh 8x4 sheet of MDF and its fine for a while but then the warping/curling starts (I work in a fairly humid environment). The long edges invariably start to lift off as the board curls (cups?). This used to mean flipping the board, vacuuming the vacuum table channels, re skimming the surface and all would be well.... until it started lifting off/curling again and the process would have to be repeated. I was doing it once a week at least.

I tried bolting the thing down but still little gaps would appear along the edges - into which would go dust etc. This way the vacuum/spoil board is a perfect seal forever. Will never warp or lift off again.

It's just one more job that I now no longer have to do.