Vacuum plenum

[dingwall]

I'm gravitating toward an aluminum vacuum grid table top, but need to build a plenum to support the grid plate.

I'm thinking the plenum needs to be bolted to the table, then surfaced before mounting the grid plate.

I'm thinking 1/2" aluminum plate at the moment. Does anyone have experience using cast aluminum jig plate vs regular plate for large surfaces?

[conceptmachine]

Sheldon,
Cast jig plate will be the way to go but be prepared for the "sticker shock".I priced a plate a few weeks ago for the same idea and if i remember it was around $1600.00.
-shawn

[Brady Watson]

You'd be better off putting the AL plate below the grid & bleeder, than making the plate the bleeder, in my opinion. I hear a lot of guys complaining that they can't keep their table flat. If you glue every layer of your table together you should not be having problems with flatness. I get every season where I live & my table stays very flat. I use 2 sheets of Medex glued together, then machine my parts with or without my BradyVac grid.

-B

[conceptmachine]

Brady,
I'm not familar with medex,is it similar to extira?Do you use the 2 sheet's of medex for the table base and spoilboard?I need to redo my setup the mdf spoiboard warps the day after i surface it.I know it's due to the fact that it's screwed down instead of glued so when i redo it i want to go with a good setup.
thanks
-shawn

[Brady Watson]

Shawn,
You can check out Medex specs here: http://www.sierrapine.com/products/m...ex/default.asp

I have been using it from day 1 (5yrs) and it has worked out really well. It is like MDF, but contains plastic fillers that make it more stable. They didn't say it was exterior grade when I 1st bought it, but it did say it was 'moisture resistant', which I felt was what I needed.

-B

[paco]

Does wood fiber and plastic composites glue up well?.. with wood glue?

[Brady Watson]

Paco,
If you are calling Sintra/Komatex PVC a composite...no. You need to A) Scuff the back side of the PVC liberally with 40 or 60 grit sandpaper to create some mechanical tooth & B) Use a polyurethane glue such as Gorilla Glue, which I can verify that it works when gluing MDF to PVC for vacuum. Countersunken holes and Kreg screws also wouldn't be a bad idea if using PVC.

-B

[conceptmachine]

Thanks Brady
-shawn

[eidietis]

Has anyone used a sheet PVC material such as AZEK to contruct a plenum grid? Any thoughts on this idea?

[stockbub]

I have often wondered the same thing. No leaks, Flater. Seen one on expensive table, but where to get a sheet that big?