Recently constructed a vacuum clamping system using Joe Woodworking plans. have a GAST vacuum pump going to -22Hg with a manifold system. I''m trying to mill flat aluminum stock and using the vacuum clamping system to hold the stock. However it doesn't seem to hold the stock solid using the no creep sealing tape that Joe sells. I'm milling out a 12.5" long by 2" wide by 3/8th thick aluminum and need to mill around the entire piece and then do a cut out in the center. I'm afraid the vacuum won't hold the stock tight enough and move messing up the cut. I though about milling out the center first with the stock clamped in a vice and supported on the one end, then clamp the piece using the center cutout to hold the stock.
Any ideas that I could use to increase the holding power of the vacuum system so I don't have to re-chuck the stock??
ben