Vacuum pumps

[Kyle Iwamoto]

The compressor generated system, Holdfast is pretty much turn-key. You can buy all the parts from them, INCLUDING a MT adapter for your chuck. Take your piece (with the chuck) off and the adapter and chuck goes in the tailstock. Your piece wil be perfectly centered when you vacuum the piece to your headstock. I tried (failed) turning an adapter that would be perfectly straight, but I only could get it pretty close.

Holdfast system does have limits, biggest problem is that it does not pull lots of air, so holding porous woods is not possible. It is reasonably priced, IMO.

[Leo Van Der Loo]

Here in lies more confusion for me.... where does a compressor come into play in this set up. I have a 30 gallon compressor in my shop, does that open up my options, or do I need a vacuum pump no matter what??

The vacuum is generated with a Venturi, like the Carburator on a engine that uses the airflow to make vacuum to suck the gasoline into the airstream to make the engine able to run.

https://en.wikipedia.org/wiki/Venturi_effect

So your compressor is used to make the vacuum and the Venturi becomes the “vacuum pump” with the moving air the only moving part.

Venturi type pumps come in many sizes, and can move lots of air, often very noisy for the fast flowing and turbulent air, they are very good at moving volatile fluids for instance, as theres are no combustion hazards with these pumps.

HTH

[Derek Voigt]

But then I just realized that if I use my compressor to vacuum chuck, then I won't be able to power sand at the same time.

I did find the spec on this specific motor, but not really sure what specs a motor should have:
Capture.JPG

[Derek Voigt]

Also, could the same vacuum pump for turning be used to run a vacuum press? The function of "it provides vacuum" is the same, but is one more demanding then the other that would require different things.

[hu lowery]

But then I just realized that if I use my compressor to vacuum chuck, then I won't be able to power sand at the same time.

I did find the spec on this specific motor, but not really sure what specs a motor should have:
Capture.JPG

These same pumps can be used as a vacuum pump or compressor. The unit this chart is for was used as a compressor originally best I can read. I don't know how to translate possible CFM of pressure to possible CFM of vacuum. However the one horse motor is the larger motor and seems to have only been offered on one unit. Best I recall, the most CFM of vacuum was over six CFM which would pull a fair sized vacuum table I believe. I assume if you had issues you could just throw a sheet of rubber over some of the open holes on the top of a large vacuum table to reduce leakage. CFM measures volume of course not vacuum strength so it has more to do with how quick a vacuum is pulled than how much as long as the leakage isn't too great. A small pump will eventually pull the same load as a large one if there is no leakage as a very embarrassed plant worker discovered when he sucked a tank that held hundreds of gallons flat with a very small vacuum pump!

These pumps are often used as the compressors that you stick money in and air tires with at most self-service stations now to give some idea of volume.

The venturi type vacuum units that run off of a compressor pull a lot of CFM, seven to fifteen. Many compressors can't even power one and the annoyance of a compressor running nonstop to power the very inefficient seeming venturi unit doesn't seem a plus to me. The wear and tear on a compressor is considerable too. The vacuum pump runs full time but isn't nearly as noisy. I'm sure a vacuum switch could be had to cut it off but mine at least would still be running most or all of the time with the leakage I have. I open a valve to a filtered inlet to let in outside air to control vacuum pressure.

hu

[Larry Matchett]

The Frugal systems are great. The one I have has a Gast pump. Since the one you are looking at one that has a tank the pump will not need to run continuously which is a real plus especially if you decide to get into using a vacuum chamber for casting or if you do some laminating. One of my club members made one and it is terrific. I also have a holdfast system and it works but not nearly as well as my frugal system. Anything that pulls 27" will work very well. Don't buy a pump that uses oil unless you want oil mist all over the place especially the cheap ones from the Chinese store.

[Leo Van Der Loo]

Also, could the same vacuum pump for turning be used to run a vacuum press? The function of "it provides vacuum" is the same, but is one more demanding then the other that would require different things.

A sealed vacuum chamber, like a bag used as vacuum press needs only to be brought to the vacuum pressure that is wanted/needed, and then can be left, this is of course for as long as there is no leakage in the bag.

So there is very little work to be done for that.

For vacuum chucking on a lathe there is always leakage, some through the wood, some through the chuck seals and also through the rotary adaptor, so you can’t turn the pump off as you can in a good vacuum press.

As for the tank on this unit it would give you very little time before that small amount of vacuum is replaced with leaked air, though it can give you a few seconds to safely stop the lathe if your vacuum pump quits, (like when overheated, as the unit is protected and will quit when it gets too hot)

[James Combs]

I have been toying with the idea of adding a vacuum pump to my collection of tools and have the opportunity to purchase one second hand 1HP Thomas pump
with a small tank. Apparently it is lightly used and was previously used for vacuum chucking previously. He is asking 300 for the set up. Is that a far deal? Is a tank really needed for this purpose, seems like tanks go with compressors and not for vacuuming? Is there a better "entry level" set up for the casual user that I should be considering instead?

thanks,
Derek

Hi Derek, You have gotten some great info here but I still sense some confusion. I have built my on system from a pawn-shop vacuum pump, it has been a while but I did a basic diagram of a wood shop vacuum system that covers chucking and using the pump for a vacuum chamber. Perhaps it will help, see this PDF file. My original thread may also help. If you do a search on "vacuum chuck" you will find similar threads from other DIYers.