looong reply!
Bart, go to
http://www.joewoodworker.com/veneering/vacuumchucking.htm.
That gets you to the heart of vacuum rotary adapters and chucks. Then poke around and discover how you can build the entire system.
I taught vacuum clamping in a woodworking class in the middle 90's, long before it became popular with woodworkers. I truly wish this site had been available then. It's got everything you need to know.
Lots of different ways to get a vacuum pump, but there are compromises whatever you choose. Most commonly available are the 220V rotary vane pumps from Surplus Center. 110v models used to be plentiful but not so much now. Avoid venturi models unless you have a really large capacity air compressor. Shop vacs have been used, but the motor has insufficient cooling to last long. Refrigerator vac pumps have been used, but usually the reason a refrigerator fails is the pump! My classes seemed to have tried them all. Bottom line was a rotary vane pump was the better choice from many standpoints. Relatively inexpensive, easily repaired.
Don't get wound up in either horsepower or CFM. Doesn't take much horsepower to turn a pump over. CFM is an issue for production shops where waiting a few extra seconds for the vacuum to be pulled is perceived to be an issue. Time is money, ya know!
Also don't get excited by how many inches of mercury the pump can draw. I have heard numbers bandied about that rival NASA vacuum applications! A used pump that will draw at least 24-25 inches of mercury will work just fine for a long time. If it is a rotary vane pump, when those numbers go down, simply get the repair kit and rebuild it.
Caveat: always filter the air going
into the pump. The air comes from the chuck through the rotary adapter, into the pump, and exhausts to the atmosphere. Put the filter between the rotary adapter and the pump. It is exactly opposite of an air compressor. Sometimes it is hard to keep the ol' brain wrapped around that concept.
Also, with regard to tanks; for vacuum veneer press operations I can see their value. Not yet convinced for turning applications. Be happy to explain my thinking if anyone is interested.
Read Joe's site, and then if you have questions or comments, fire away. I'll be happy to share my experiences (and those of my students) with you. I have three pumps, plus the venturi (visual aid for the class).
Also understand that Joe's site is focused largely on veneering applications, so his pump systems are designed accordingly. Suggesting perhaps a bit of overkill for turning.
For the lathe I would design a much simpler and more inexpensive system.