Vacuum press without a lot of work

[Randy Roberts]

I wanted to make a box to holding a tuner, picks, and spare sets of strings to go with a guitar I made for my son. I decided I wanted to have it match the guitar. To do so I needed to veneer the woods I used in making the guitar onto some plywood, which I’ve never done before.
Several years ago I made this vacuum pump work bench using an old compressor from a chest freezer.

[Randy Roberts]

One of the vacuum taps goes to a hole in the top.

[Randy Roberts]

The top of the bench isn’t really large enough to use, so I was trying to figure out a way to get a larger surface to work on without the hassle of rebuilding the bench just for a one off project. The following pictures show what I ended up with.

[Randy Roberts]

I simply took a large piece of ¾ inch Formica topped particleboard and duplicated the hole just like in the table’s top.

[Randy Roberts]

To keep the leaky particleboard from breaking the seal of the vacuum, I just fit a piece of tubing into the hole after coating the surface of the hole with silicone caulk. A little closed cell weather-stripping seals between the two surfaces.

[Randy Roberts]

The same weather-stripping around the edges of the top forms the seal for the vacuum table top.

[Randy Roberts]

Plastic screen allows air to evacuate from all areas of the table top to the central hole.

[Randy Roberts]

Rubber membrane lies over the top.

[Randy Roberts]

Clamped pieces of wood hold the membrane down to the table top. They are clamped down outside of the weather-stripping which let me open and close the membrane over and over without smashing the weather-stripping down flat.

[Randy Roberts]

The plywood with the veneer (in this case glued with 5 minute epoxy to speed up getting the job done) is wrapped with a layer of wax paper to prevent squeeze out from gluing the work to the table top.

[Randy Roberts]

It breaks down to store easily, and it worked well without having to build a frame, seal all the possible places a normal vacuum frame can leak, and the technique allows scaling up to pretty much any size of vacuum table that you would need.

[Jason Rodgers]

Clamped pieces of wood hold the membrane down to the table top. They are clamped down outside of the weather-stripping which let me open and close the membrane over and over without smashing the weather-stripping down flat.

I am constantly amazed at how many ways one can set up and use a vacuum system. I am really not getting very creative with mine!

So, in this pic, the rubber membrane goes over the seal strip, and is held down on the other side with the wood slats. Do you push them right up behind the strips, and then the vacuum is enough to hold the membrane to the seal? What membrane material are you using?

[Randy Roberts]

Yes, I wanted as large an area as I could get with the piece of Formica I had available, so I put the gasket as close to the edge as I could and still have space for the hold down wood strips. But I think it helped to place them up at the edge of the gasket. I "re-assembled it 8 times for veneering the four boards I needed, and it pulled the vacuum each time without any fussing or leaking at all. I also used wood strips that had a little warp to them and used the convex face facing the formica. When clamping the wood strips down I just gave a gentle pull to the membrane as I clamped it, and that took out any wrinkles that the membrane had. I was using 5 minute epoxy, and it worked fine with plenty of time to put the frame together and pull the vacuum each time, if that gives you any idea of how quick it is.

I got the membrane from Joe Woodworker. It was years ago, and I am remembering it as being a type of rubber, but I don't see any rubber membrane listed there now. The Dura-Max Elite polyurethane they list sounds like it would be the best bet from what I find there. I've only tried vinyl once and didn't like it a whole lot, but I don't see why it wouldn't work.

If you look at the Joe Woodworker site, they have directions for making a really nice vacuum frame press, and I built something similar for gluing braces down. It's really handy to be able to just lift and lower the whole frame instead of "re-assembling" the membrane and wood pieces each time you put a workpiece into the frame. But if you read their tutorial for building one you can get an idea of how many places you can have leaks, and how much work it takes to make one. With what I did, you pretty much eliminate all those sources of leaks, as the frame etc. is all outside of the vacuum system. And it also leaves you with all your materials intact to use for some other project down the road instead of being tied up in a particular fixed configuration.

If you decide to make a different size down the road, all you need to invest is a sheet of Formica, 1" of the clear (white thread reinforced) tubing and dab of silicone for the hole in the formica, weather-stripping,and enough 2 x 2or whatever wood for the outer frame.
And you don't need a table like mine, Just plug a barbed fitting, or however you are currently hooking up your vacuum line now, into your piece of tube before you stick it into the hole in the Formica. If you place the hole near one edge of the Formica sheet, you can put the Formica on any table or workbench and just have it overhang the workbench enough for the fitting underneath to hang down.

[Jason Rodgers]

Not that I glue up top/back bracing very often, but my mind is working on how this method could be used for that purpose without creating a full-on frame with lid system. I also like the use of screen for the breathing layer.

[Randy Roberts]

Not that I glue up top/back bracing very often

You really ought to try it, at least once <G>....

If you are using hot hide glue for braces, I think it would be worth building a regular vacuum frame that you can lift and lower all as one piece. Although I found it worked really well to use a dished board with a similar hole in it with a gasket around the dish to hold the top/ back in it's correct radius, and use a frame with it's own vacuum line for pressing the braces.

[Jason Rodgers]

I'll have you know that I've glued up five tops and backs in the go-bar deck!

No, I use fish glue, so the longer clamp time probably wouldn't work with a vacuum system. I do like the idea of making double-tops, backs, and laminated sides, though, so your setup would definitely work for that. And the break-down-ability of the components works VERY well for my tiny shop.

[Tom Sommerville]

I've been using a Thomas pump but it's loud and I can't stand to be around it.

There used to be information on the fridge/freezer compressor set-up. They are quiet.
I got a compressor from a junk dealer, but it needs a start capacitor to run.
If anyone knows about how wiring the thing, and how to keep the oil from slinging
out through the exhaust, I'd appreciate the tips.

[Barry Daniels]

The Joe Woodworker site has a lot of info on vacuum pumps. But I don't know if they specifically address your issues.

[David King]

Tom,
There something called a "hard start capacitor" designed for use in old fridges that can't start when the pressure is up. They are sized by fractional HP and on up. They cost about $15 on ebay and amazon but you would need to look for schematics on how to wire everything up. It's quite possible the a normal start cap would work for you but fridge compressors have a lot of bizarre and expensive parts in that circuit that go bad and will universally get replaced with "Hard start caps".

I would add an air compressor muffler and a capture jar to the output of the fridge pump to keep atomized compressor oil out of the room.

[Randy Roberts]

If you use a refrigerator pump, I can't picture how you would need a muffler. I can hardly tell when mine's on or off.

But I agree it's nice to have some means of collecting spit out lubricant as it comes out of the exhaust. I've tried a number of things, from a plastic IV bag to a blood collection bottle that has a micro-screen in it to filter out microscopic blood clots, to a plain old water bottle, and you still will get some odor of the lubricant no matter what you do.

I finally just ran a small diameter piece of tubing out the garage door to the outside.

Even when it was running the exhaust straight into the room, I never had any problem from it getting on the wood and causing any finish problems or anything (I've only used shellac).