[DHay13]

Frustrating! I just spent about 45 minutes typing this up and hit Submit, and everything looked good. Then nothing!

So I'll try this again.

I have a 24" x 24" CNC machine. I currently have 2 3/4" sheets of MDF copied from CNCRobs setup. The bottom one has the vacuum channels cut in and the top one has 1.25" square grid cut in it. Bottom line is I screwed up the top piece and need to replace it. I was going to use a Shop-Vac for vacuum. Now I'm looking into buying a small vacuum pump off eBay. The ones I am looking at are about .5 HP and pull 7 CFM. My setup has 9 vacuum holes to pull vacuum through the top. I was planning to plug off 7 or 8 holes and only use 1 or 2 and section it off under my spoil board.

Any suggestions? Trying to keep it under $300 as I still haven't made any money with this machine yet.

EDIT:
Just wanted to add that I currently have a few pieces of 1/4" aluminum about 2" x 1". I put a piece on each side of my spoilboard. The first 2 are slid into the groove of my grid and the spoiboard pushed up tight to these. The last 2 are inserted into the grooves on the other sides of the spoilboard and have 1/4" screws going through them and they get tightened to to sides of the spoilboard to force them against the first 2. The problem I have with this is that the aluminum angles backwards and the screws end up lifting the spoilboard. I am afraid to force the aluminum down into the grooves further as I have already broke a few of the grid squares off, which is why I'm replacing it.

I was considering HDPE but have read about static issues.

[JerryBurks]

I am quite happy with my new supercharger vacuum pump. Cost me less than $300 but obviously "some assembly required" and you need to find a good offer on a used supercharger.

But for that you get 3hp, 80-100 cfm, 10-12" Hg vacuum and a noise that makes a planer envious.

[DHay13]

Saw that one. Too elaborate for me. Besides, I'm a car guy and would be too tempted to use it on a new project:idea:.

[DHay13]

Well I ordered the kit from Joes woodworking the other day. Supposed to be here Monday. I ordered the cycle kit. Can I cycle it or will it have to run continuous?

[DHay13]

Got the kit today. Started to assemble it. I'm using MDF for my table. Any tricks or tips to attaching the hose/fitting to the MDF? Glue? Silicone? Just screwed in?

[DHay13]

Got the pump from joewoodworker and got that all assembled using the EVS kit and about a 5-7 gallon air tank I had laying around as a reservoir. I pumped it up to about 24.5" vacuum and left it sit overnight. It was not hooked to my table yet, just had the ball valve closed. About 12 hours later had 24" vacuum so holding good there. I made up a new MDF vacuum table using (2) 3/4" sheets of MDF. Same design as before. I cut my vacuum channel in the bottom piece and put 2 coats of Zinnsers shellac on it. Only cut the through holes in the top piece and inserted my .250 cord seal and bolted the new top down. Initially I cut the cord channel at about .254 but as soon as I opened the valve all the air leaked out. So I surfaced about .05 off the top of the lower table so now the cord channel is .200 deep. I coated the bottom of the upper table (and all edges and holes) with the shellac but not the top. It slowly lost vacuum when I opened the valve. I tried laying a garbage bag over the table and that didn't seem to make a difference. So I put one coat of shellac on the top and it was better but still losing vacuum. Plan to put a second coat on it tonight.

Question is, is shellac the right choice? Will a second coat make that much of a difference? It takes about a minute to go from 24.5" to 0 with the pump running. I taped up the edges too so my guess is it has to be sucking through the top board?

[diyengineer]

$300 bucks, i would go with a Thomas twin piston pump off ebay and buy the rebuild kit. You can get one for under $100 probably already factory rebuilt off ebay. The parts are cheap and they work through hell or high water. Here is 6 on a vacuum cart i have, 12 cylinders total.