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Vacuum Chuck: repurposed A/C pump or Gast?

J

Jed Malcore

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Feb 5, 2015
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Maine
I'm debating between repurposing an A/C pump for vacuum chucking or buying a used Gast off Ebay. Any thoughts? Pros/cons? Suggestions? Comments? Thanks!
 
Jed Malcore said:
I'm debating between repurposing an A/C pump for vacuum chucking or buying a used Gast off Ebay. Any thoughts? Pros/cons? Suggestions? Comments? Thanks!
Click to expand...
Jed,
I bought a gast pump and plumbing kit from ONEWAY around 2000 it is still going strong. I have never bought a vacuum Chuck having made all my own except a few Don Doyle of rubber chucky fame gave me to test when he was refining the mix for the gaskets.

I know guys who have built perfectly fine pumps from salvaged commercial cooling pumps and from car AC PUMPS adding a motor.
eBay is always sort of a gamble but I have gotten a few things from eBay with no serious disappointment.
You should check out the Frugalvacuumchuck.com. People seem quite pleased with his products.
He has been a vendor at a couple of AAW symposiums.
Probably a bit more than eBay but you get the convenience of having everything you need besides the pump in a kit where you still have to put some things together. If nothing else you will have baseline for pricing. There is an AAW article on building a pump. I use it as a reference for the cfm the pump has to remove. I will try to look it up later.

Basic issue for vacuum pump is to have one that is reasonably quiet as they are usually run close to the lathe.

Probably the long way is saying do what you are compfortable doing.
Al
 
I've had a vacuum pump I got from JT Turning tools for about a year now. It is quiet and runs continuously for a long time with no issues. I have it sitting on a shelf below my lathe.

I recall I paid about $200 or so (I bought some other things at the time) and it's on their site for $210 plus shipping.

I put a link below if you want to look at it. I'm in no way affiliated, but called and bugged them repeatedly while OCDing on research and they were uncommonly nice. A lot like the folks at Robust. You call and sometimes the owner answers.

http://jtturningtools.com/vacuumpumps-kits
 
I lucked out on a Gast vacuum pump on eBay several years ago from a company that was disposing of unused lab equipment. The pump was like new and I bought it for about $50 if I recall correctly. If you buy from a dealer on eBay be sure to look at their approval rating and read the negative comments. The FrugalVacuumChuck.com guy that Al mentioned has been at SWAT several times and his systems sell like hot cakes. I know several of my fellow club members who bought their vacuum system from him and have been very happy.

For vacuum chucking, you don't really need a hard vacuum ... a vacuum of about 25 in-Hg is sufficient, but what is important is a high flow capability. An air-conditioner vacuum pump is good where you need a hard vacuum, but flow rate isn't a priority ... vacuum veneering or vacuum stabilizing are two examples. An air-conditioner vacuum pump might work when chucking some wood, but might not hold with wood that has a lot of air leakage.
 
I have the Frugal Vacuum system and it works very well. Mine pretty much came complete, I remember buying an hose adapter to connect the J.T. turning adapter. It will draw 26 Hg and enough volume to hold most bowls with some leakage.
 
I have done both.( I am assuming you are talking about a belt driven car A/C unit). The repurposed AC unit is a bit more noisy in that you have a pump to drive the AC unit and you have the exposed belt drive. It also has oil that needs to be occasionally changed.
I have had several Gast pumps, my current is a 10 CFM I bought off eBay at about $125, and new is in the $800 range. Rebuild kits are in the $100-$150 range.
But this one in the classifieds is a goods deal, assuming it is still available
http://www.aawforum.org/community/index.php?threads/robinair-vacuum-pump.12364/
 
I started with an Air conditioning compressor from a car. It worked fine. It was a little noisy by not bad. The biggest problem was it wanted to blow out oil. I made sort of a muffler with steel wool in it to contain the oil. Eventually I got a Ghast compressor. Much better. If I was setting up a vacuum chuck today I would look at the Venturi style if you already own a compressor. The units are much smaller.
 
hockenbery said:
Jed,
I bought a gast pump and plumbing kit from ONEWAY around 2000 it is still going strong. I have never bought a vacuum Chuck having made all my own except a few Don Doyle of rubber chucky fame gave me to test when he was refining the mix for the gaskets.

I know guys who have built perfectly fine pumps from salvaged commercial cooling pumps and from car AC PUMPS adding a motor.
eBay is always sort of a gamble but I have gotten a few things from eBay with no serious disappointment.
You should check out the Frugalvacuumchuck.com. People seem quite pleased with his products.
He has been a vendor at a couple of AAW symposiums.
Probably a bit more than eBay but you get the convenience of having everything you need besides the pump in a kit where you still have to put some things together. If nothing else you will have baseline for pricing. There is an AAW article on building a pump. I use it as a reference for the cfm the pump has to remove. I will try to look it up later.

Basic issue for vacuum pump is to have one that is reasonably quiet as they are usually run close to the lathe.

Probably the long way is saying do what you are compfortable doing.
Al
Click to expand...
It pays off to read the forum! Thanks for the info...
 
i have used a shop vac for a vacuum pump on lathes that have an outboard spindle.
Turn an adaptor from wood.
The adapter has a through hole slightly larger than the spindle and a socket that fits tightly in or over the vacuum hose.

The spindle must turn freely when the adapter is placed over the spindle.
While the adapter will usually snug itself to the spindle when the vac is on it is prudent to secure the hose from falling off by clamping the hose to something or taping it to the head stock.
This system will leak at the adapter but the shop vac moves a lot of cfm.
I stick to bowls 1/2"+ wall thickness since the system relies on leakage to control the vacuum.

The system will hold a bowl and using one will quickly convince you thatvacumm works.
 
One problem with using a shop vac is that most of them depend on constant air flow to provide cooling air for the motor. When using the shop vac in this manner, the air flow is reduced to almost nothing. There are some high-end vacs (such as Fein) that use a separate airflow to cool the motor so that a blocked intake won't overheat the motor.
 
Bill Boehme said:
One problem with using a shop vac is that most of them depend on constant air flow to provide cooling air for the motor. When using the shop vac in this manner, the air flow is reduced to almost nothing. There are some high-end vacs (such as Fein) that use a separate airflow to cool the motor so that a blocked intake won't overheat the motor.
Click to expand...

Good point. The way vacuum is usually employed is for short durations.
Typically a few minutes to finish turn and sand the bottom of a bowl or platter.
This is typically a 5-10 Minute job. I know several people who have used shop vacs quite a bit for turning the bottoms of bowls withipout burning out the shop vacs. Maybe they were lucky or enough cooling air gets through from leakage.

I've done 4-5 bowls with a shop vac. No Obvious ill effects on the shop vac.

Shop vacs, even the fein are too loud.
 
The obvious ill effect is when the motor stops running or is barely running on its way to dying. 😀

Overheating causes slow deterioration by cooking the insulating varnish on the windings and the iron laminations that make up the field core of the motor. The result isn't obvious, but what is happening to the core is that this breakdown Allows eddy currents in the iron that can eventually cause the motor to run hot even with normal cooling air. Excess heat deteriorates the insulating varnish on the windings resulting in more heating and loss of power. It eventually gets to the point where there is an "avalanche" type breakdown leading to the demise of the motor.

How hot is too hot? If you could touch the bare frame of the motor (which you can't without disassembling the vac), but if it is too hot to keep your hand on it then it has been overheated. In hot weather, I think that this could happen in one or two minutes. Maybe a lot longer if the shop is really cold. In any event, I think that it would be good to cool the motor off after using it in this manner. Maybe remove the dust bag, pleated filter, and hose and let the vac run for several minutes.
 
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