# a/c compressor -- pump for vacuum chuck?



## duncsuss (May 11, 2015)

I've been thinking for some time about assembling a vacuum chuck, and as luck would have it one of our window a/c units had to be replaced this weekend. There's nothing wrong with the compressor (afaik).

Any idea if it will work as a pump for a vacuum chuck? I know that Curtis ( @TurnTex ) has links to a 'cheap sucker' using a beer keg cooler unit, but I don't know if the one I have will draw enough CFM and/or necessary vacuum depth (inches of Hg) to use for a vacuum chuck.

(Or whether it would do double-duty if I should want to get into stabilizing at some point in the future.)


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## Schroedc (May 11, 2015)

I'll be interested to see what folks say... I've got an extra older pump and I keep thinking about adding a vac chuck to the oneway. I've got most of what I'd need......


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## duncsuss (May 13, 2015)

I guess I'll have to be the pioneer -- going to have to "suck it and see" 

I've got a friend with a chamber (one of Curtis's) that has the gauge, etc, and he uses a Robinair pump -- if I can fit a hose to it, I can check what my pump will draw and compare it to his. That will at least tell me how deep a vacuum it will pull -- but I'm not sure how to check CFM.


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## Schroedc (May 13, 2015)

duncsuss said:


> I guess I'll have to be the pioneer -- going to have to "suck it and see"
> 
> I've got a friend with a chamber (one of Curtis's) that has the gauge, etc, and he uses a Robinair pump -- if I can fit a hose to it, I can check what my pump will draw and compare it to his. That will at least tell me how deep a vacuum it will pull -- but I'm not sure how to check CFM.


 
I don't know about CFM needs for vacuum chucking but for stabilization, as long as it draws a deep enough vac, CFM isn't really all that much of an issue unless you're running a huge chamber, it just takes a little longer to get down to the max vac. Considering most chambers are only a couple cubic feet or so you don't have that much air to move. I'd think that you'd actually have more foaming issues with a high cfm pump as the air is really rushing out of the wood as opposed to a lower cfm where it eases out a little slower.......


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## duncsuss (May 13, 2015)

Schroedc said:


> CFM isn't really all that much of an issue unless you're running a huge chamber, it just takes a little longer to get down to the max vac.



That's my understanding too. I think if the CFM is too low, leakage (around the edge of the chuck or through cracks/grain in the wood) can cause problems with a vacuum chuck.


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## CWS (May 13, 2015)

I think the compressor will work ok. I use vacuum chucks often on my Powermatic. Just make sure you don't have any leaks.
Curt

Reactions: Thank You! 1


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## MikeMD (May 14, 2015)

Duncan, I found at least 3 Gast rotary vein vacuum pumps in near perfect condition for $100 on CL when I was looking for a vacuum pump. I bought every one of them. I kept one and the other two went to buddies (turners) that needed them, too. Not sure if that is what you'd consider cheap or not. I believe these things go for $350+ new.


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## duncsuss (May 14, 2015)

MikeMD said:


> Duncan, I found at least 3 Gast rotary vein vacuum pumps in near perfect condition for $100 on CL when I was looking for a vacuum pump. I bought every one of them. I kept one and the other two went to buddies (turners) that needed them, too. Not sure if that is what you'd consider cheap or not. I believe these things go for $350+ new.


Thanks for the tip -- if the pump/compressor out of this ac unit won't do the job, I'll definitely scan Craigslist to see what's available round here.


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## TurnTex (May 17, 2015)

A typical refrigerator compressor turned into a vacuum pump will pull around 28.5" Hg at my elevation which is a 98.2% vacuum. They don't move much air though and take longer to pull down a stabilizing chamber so I think you may have issues with vacuum chucking unless the wood is not porous. You need higher CFM for vacuum chucking to compensate for the leakage through the wood. It may be enough, though. For stabilizing, it will work ok. I prefer to see a higher vac but for the money, it will do ok. Regardless, don't use a small hose for your vacuum chucking. A 1/4" diameter hose only allows approximately .75 CFM through it. That is why a 3CFM pump and a 10 CFM pump will both pull down any size stabilizing chamber to full vac in the same amount of time assuming they are both using the same size hose.

Reactions: Thank You! 1


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## duncsuss (May 17, 2015)

Thanks for this information, Curtis.

It makes me a bit leery of using this pump for a vacuum chuck ... by definition there's a lot of time and effort invested in getting a piece to the point where air pressure is the only thing holding the wood to the headstock. That's no time to discover the pump is under-powered

Reactions: Agree 2


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