opinion needed for vacuum pump please

[Jeremy Yorke]

I was looking for a v. pump to set-up a vacuum press when I came across this pump from HVAC co. that the owner said did not want. he said that someone borrowed it and returned it because it didn't work right(???). he offered it for me for 50 bucks.I had it run for good half an hour with no problem I hooked a vacuum gauge and the needle was steady. how else can you test the this pump but most important is it worth $ 50.00. it needs a cleanup for sure and from exhaust pipe air comes out with small amount of oil.most of the pumps that you see now days are Chinese made but this is made in the USA, but than again it could be at the end of it's life
your opinion is very much valued.
thanks.



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[Dan Friedrichs]

...and from exhaust pipe air comes out with small amount of oil.

I've seen lots of high vacuum pumps that spit out a mist of oil (especially at start-up). Sometimes there's a oil trap on the exhaust specifically to stop this - I don't see one on this pump, but I wouldn't worry about that.

Sorry - I don't know anything else. Just wanted to tell you that I wouldn't worry about the oil...

[David DeCristoforo]

Those pumps originally sold for around $150. So fifty bucks is reasonable if it works. All a vacuum pump has to do is draw air. If you tested this pump and it can pull a vacuum of 25 inHG or better, it will work for a vacuum press. But you will have a better system if you construct some reservoir tanks. Check out some of the homemade systems on the Joe Woodworker site (joewoodworker.com). Pretty easy to cobble up, JW has all of the parts and full plans you would need. But, in reality, you could hook that pump directly to a vacuum bag and go (again, of course, assuming that it works properly).

[Jeremy Yorke]

thanks for the replies
the needle at vacuum gauge stays steady at 28 PSI. Is there is a way to check the motor for conditions?

[David DeCristoforo]

If the motor runs and does not make any weird noises, it's probably fine.

[Hugh Watling]

28 psi of vacuum is impossible!
A perfect vacuum is 29.9 in. of mercury which is what I believe you meant.

[David DeCristoforo]

"28 psi of vacuum is impossible!
A perfect vacuum is 29.9 in. of mercury which is what I believe you meant."

Yes. It's Saturday morning! Sorry...

Vacuum is measured in "inches (or MM) of mercury" (Hg) with one inch of mercury (1 inHg) approximately equal to .5 PSI. So an absolute vacuum (impossible to achieve) would equal 14.7 PSI or approximately 29.4 inHg at sea level. More typical is around 13 PSI or 26 inHg. Jeremy's gauge is, obviously, measuring inHG, not PSI. The best I have ever been able to achieve was 27 inHg or very close to 13.5 PSI.

[john bateman]

At 3cfm that should work for all but the hugest of vac projects.
FWIW I have a regulator on mine which turns the pump off at 22in and back on when the bag bleeds down to 18in. I use Titebond Cold Press veneer glue and have never had any failures at those vacuum levels.

[Jeremy Yorke]

thank you for correcting me. it produces about 28 hg steady however I do hear some rattling inside the motor. the guy let me check it out before I buy it.

[Bill Arnold]

It sounds like the pump you have will work great. As others have said, contact joewoodworker dot com and get all the the parts you need. Here are some photos of my pump system. It's one of many featured on Joe's website.






The box on the top left houses a vacuum switch set to turn the pump off at 22inHg and on at 18inHg. The reservoir is 4" PVC cut to a convenient length and plumbed together.

I use a variety of bags depending on the project. I started with a vinyl shower curtain from Walmart for the first small items I did. I now use some heavy vinyl material available at most fabric shops. There is some really expensive bag material available but you don't need to spend that kind of money. My bag closure is a two-piece PVC assembly; one length of 1/2" and another of 3/4". The 3/4" pipe is cut with a bandsaw along its length to about 3/4 of it remains solid. The 1/2" pipe pops inside it with the open end of the bag in between the two pipes.

My pump emits a fine mist of oil which can be contained with a piece of fine steel wool.

[Bill Arnold]

I use a cold press glue for flat panels. Titebond is used by a lot of people. I got some glue from JWW that has some solids in it to aid in keeping the glue from penetrating solid veneers. On paper-backed veneer, I've used Titebond II with no issues.

For bent laminations, I use plastic resin glue. It's harder than white or yellow glue so I get little, if any, springback.

[Mike Cutler]

Jeremy


That pump should work just fine. It is the same type of pump I use to calibrate vacuum switches at work. Build a setup like Bill's and you'll be OK.

For the record. PSI/psig is a unit of pressure measurement that begins at 14.7 psia, +/- barometric pressure. 0 psi equals 14.7 psia, or 0" hg (mercury), or 29.92" hg(a) absolute. PSI is not a unit of measurement for vacuum. PSIA is an equivalent atmospheric measurement that can be correlated to vacuum.
I'm not trying to nit pick here. It's just that when you go to order parts to build your rig you won't confuse the issue and end up with the wrong pressure and control switches, or regulator.
You can hook the pump up straight to the bag, but a reserve volume with an automatic vacuum control switch would save wear and tear on the pump and motor.

I've probably built a dozen or more vacuum rigs at work over the years. They're really not that complicated.

[Steve Rowe]

Why pay $50 for used when you can pay $54.95 for a new Gast vacuum pump? The motor is 220V which could be a downside if you don't have it. I purchased this pump 5 years ago and use it for vacuum chucking on the lathe. The source is:

https://www.surpluscenter.com/item.a...4-1669&catname=

Steve

[Bill Arnold]

Why pay $50 for used when you can pay $54.95 for a new Gast vacuum pump? The motor is 220V which could be a downside if you don't have it. I purchased this pump 5 years ago and use it for vacuum chucking on the lathe. The source is:

https://www.surpluscenter.com/item.a...4-1669&catname=

Steve

Look again. The listing says:
1/4 HP Rotary Vacuum Pump/Compressor
Used, GAST model 0522-P335-G509DAX.

[Michael Weber]

Look again. The listing says:
1/4 HP Rotary Vacuum Pump/Compressor
Used, GAST model 0522-P335-G509DAX.

The rattling you hear may be the sound of the pump itself. This kind of pump often makes a kind of rattling sound once the vacuum level drops to below a certain amount. If the sound is absent with no vacuum then the motor is probably not the source of the rattle.
FWIW in vacuum work these kind of rotary pumps can only achieve a moderate vacuum level. True high vacuum levels are measured in sub micron levels. A micron being 1 millionth of a meter of mercury. Under ideal conditions an expensive rotary pump might pump to 1 micron but typically can only get to 5 or 10 microns. Higher levels of vacuum (or is that lower) require different methods like diffusion pumps.