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I am getting ready to start producing hard templates and I wanted a vacuum table to make the machining easier. I also plan to use it to make my own guitars on my machine so I wanted it to be versatile. When I priced them it was real sticker shock! So I decided to make my own.

I started by making a base that bolts down to the T-slots in the machine. On top of that I have two layers - the jig and the work piece. The jig hooks up to the vacuum pump and gets sucked down to the base. It then transfers the vacuum through hole to hold the work piece on top.

Here’s the bottom of the vacuum plate. It is ringed with that weather-strip that’s made of rubber and hollow in the middle. I sealed the corners with rubber cement. I used Gorilla glue on the first attempt but it dried to stiff and wouldn't seal to the base.



Here it is on the base which I planed flat. You can see the vacuum port on the corner with a quick release hose attached. Also, see my cool dust shroud made from cheap paint brushes? It works great! I can stand right there and I don’t need a mask.


Originally I planned to have O-Rings to seal between the fixture and the work piece but I couldn’t get it to seal. I found that just using holes provided a great seal by themselves.


Overall shot of the whole setup.


This one shows the setup in action with a real blank sucked down.


Tada! A complete template set.

Commercial vacuum chucks are crazy expensive, but everything costs more to buy than make (otherwise there'd be no profit in selling things!). You can also customize your stuff if you make it, which tends to add up long term. My first vacuum chuck was a chunk of aluminum plate I cut a grid into and used round foam cord for sealing. I put holes for pins in the squares of the grid for handling shear. For one-offs, I'll just cut a fixture into a piece of MDF or plastic or whatever's around and then face it off again when I'm done.

You need to have the sealing gasket in a channel where it can be compressed into the bottom plate to avoid deforming the piece it's holding down. Otherwise, if you were to face off a plate on top of the fixture it would end up being thick in the middle and thin on the edges. Once the gasket can compress properly, the fixture plate will sit flush on top of your base plate, so you'll also need to cut a grid or some channels in it to avoid having a pressure gradient.

It will be necessary to use gasket around your parts, and possibly pins to take side loads, when you start machining smaller or thicker parts on your fixture.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks for the comments. I have already run into some of the issues you talk about. My thoughts about the plate deformation is to put pieces of MDF around the bottom to hold the whole fixture flat and the weatherstrip around the edge to make the seal. I also had a problem with the piece losing suction after I started cutting. What I deduced was that as the bit cot dull it was forcing particles between the fixture and the work piece. I used a wider bit to cut channels under where the bit will pass and that worked well.