MDF has a finish coat on it. Skim that off and it should work.

 

how well does UHMW type material...

 

if your vac is less than super strong, you may consider ULDF. some mdf's are not so porous.

as John mentioned, you want to skim off one face, flip it over and glue it down, run the vac to hold it down for an hour or so. then paint the edges to seal them off. then run your spoilboard cut program to skim it off, and level it off.

 

Depends on the pump(s) you are using.
We use regular old MDF, with our two 10HP Becker pumps.
If you are using a vacuum cleaner motor, you might want lightweight MDF.

 

Vacuum Table Material

I also live in MA (South Shore) and I purchase Ultralight MDF from my local lumber yard. They carry both the lightweight and traditional weight MDF. The Ultralight is much more porous and it did not require a surface skim.

 

more details

WE are running a 25hp sullair pump, MDF has been fly cut top and bottom, and all edges and unused area of the 5'x10' sheet have been sealed with (3) coats of polyurethane. My issue is when I purchase locally the mtl is always different sometimes its dark like a clip board and will not allow vacuum through it. I'm looking for mtl that is lighter in color and about 1/4" thick to use over the spoil board. Have had great luck in the past but now I am struggling to find the same type of MDF. When the material that worked was ordered it was ordered as "MDF" now when I go to re-order I cant get the same material and the vendor doesn't have record of exactly what we received. Its been a couple of years since we received that good stuff. I was hoping someone out there was doing the same process and had a source for their MDF with specific material details.

Thanks,
Mark

 

Ask for super refined mdf.

Are you trying to pull vacuum through both the spoilboard and a sheet of 1/4" MDF? 1/4" MDF is much more dense than 3/4".