--- In
Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
>
> Just a note about today's task. I scrounged some tubing and made some
> adapters, got some scrap rubber gasket material, and converted my UV
> exposure box to vacuum hold-down. I used a 1/4" wide strip of rubber
> sticky-backed gasket material around the edge, drilled a hole in from
> the front and up into the space within the gasket, and made a wooden
> adapter (stopper) to connect the shop-vac to the tubing.
>
> I didn't feel much "suck" on the end of the tube with my finger, but
> the first time I hooked it up and tested it I saw the glass bow in so
> much I feared it would break!
You don't say how big the tube was, but if you can stopper it with a finger then it is probably 3/8 or 1/4 inch ID. Well, 5 psi of pull would translate to about 2 pounds pull on your fingertip. Put that on a 10x8 sheet of glass and it is the equivalent of placing 400 pounds on the glass!
I'd make an adjustable hole in the shopvac hose or in the vacuum table. It is bad for the shopvac to run without any air input anyway, the motor will overheat, and you can regulate the vacuum this way.
Steve Greenfield