Vacuum Clamp built into workbench?

I finally got my vacuum bag system set up (mucho thanks to joewoodworker.com). I've done some veneering, and now I'm thinking about making a vacuum clamp.
I had the thought that I could drill a hold through my solid maple bench top and thread an NTP male quick release onto the bottom. Then take a piece of MDF and drill a hole though it. Put some neoprene tape along the edges on both sides. Then whenever I want to vacuum clamp something, I'd blow out the hole to clear any dust/debris that might have collected, attached the vacuum pump, put the MDF over the hole, and the piece to be sanded/routed on top of the MDF. Then turn the pump on (the pump is 3cfm continuous duty rated).
Am I missing something? Ideally I'd have a foot switch to release the vacuum pressure, but as far as I can tell it should work. Thoughts?
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This is exactly what we had set up once upon a time for routing with a hand held router. Your thinking is flawless.
UA100
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It sounds like this would work great. You could make various sized pieces of MDF for clamping various sized boards.
Joe in Denver My woodworking website: www.the-wildings.com/shop/

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Bestest Handsander wrote:

Don't use MDF - it's much too leaky. Instead make your block of UHMWPE (ultra high molecular weight polyethylene). It's available from most woodworking ssources. It's not cheap but it /works/.
You don't need to drill your workbench to do this. I have a web page at http://www.iedu.com/DeSoto/assembly.html that describes how to build the kind of clamp you're describing.
BTW, I use an old recycled refrigerator compressor to provide the vacuum for my CNC router. It works /well/ (and the price was right!)
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Morris Dovey
DeSoto, Iowa USA
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MDF works just fine if you finish it. I used spray lacquer on mine. I drew a vacuum last Saturday and the piece is still locked down as tight as can be. Based on my experience, you should incorporate some type of release valve. I will probably re-design mine so that the vacuum that holds the mdf to the bench and the vvacuum that holds the workpiece are two separate lines.
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David Chamberlain wrote:

The two-line approach sounds good. I think I might have to build a few more 'pucks' to play with. I normally use multiple pucks to hold a workpiece; and for production runs have had to make a mask of 1/8" hardboard with cutouts for the pucks to keep them from shifting when the workpiece is removed. A second line would make that unnecessary - but would double the amount of tubing in the work area; and would require a second vacuum source.
I started out with UHMWPE and have never had a problem; but know a number of people who've used MDF and seen poor-to-terrible performance. I suspect that they just didn't seal the MDF as thoroughly as you did.
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Morris Dovey
DeSoto, Iowa USA
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