air vacume pump

[travisc]

I was looking thru Harbor Freight's new sale catalog, and saw a air vacume pump. ITEM 3952-0VGA it is on sale for $9.99

Venturi-type vacuum pump removes moisture from air conditioning systems so you safely add refrigerant. Easy to operate, just connect an air line and it pulls full vacuum within 2 minutes. Ideal for automotive air conditioners, home air conditioners, refrigerators, freezers, and more!
Vacuum level: 28.3" of mercury at sea level
Air consumption: 4.2 CFM
Air inlet: 1/4'' NPT

Could this be used to make a small vacume table?
I plan to cut balsa, light plywood and plexiglass, all under 1/4" thick.
And I would like to be able to hold this down flat on the table.
Any thing over 1/4" I plan to clamp or screw down.

[ger21]

I used that to build a vacuum veneer press. You'll need to build a reservoir for it, and it's quite noisy. Check out www.joewoodworker.com for plans to build a complete unit.

And yes, it should work.

[eloid]

Originally Posted by ger21 I used that to build a vacuum veneer press. You'll need to build a reservoir for it, and it's quite noisy. Check out www.joewoodworker.com for plans to build a complete unit. And yes, it should work.

do u still need a mac value if u use your compressor for your line in?
I looking for info on how many inches of Hg do u need to
hold some down for a cnc cutting ie 4x4 sheet of plywood?

[teamtexas]

The venturi works pretty good, I used one to make a vacumn molding machine for plastic. I used an old propane tank and a new 20 gal. air tank for the reserve. Only problem I had was vacumn loss was quick on large molds.

[eloid]

Originally Posted by teamtexas The venturi works pretty good, I used one to make a vacumn molding machine for plastic. I used an old propane tank and a new 20 gal. air tank for the reserve. Only problem I had was vacumn loss was quick on large molds.

so u used a compressor to create a vacumm or a pump? new to this pleas explain?

[ger21]

Originally Posted by eloid do u still need a mac value if u use your compressor for your line in? I looking for info on how many inches of Hg do u need to hold some down for a cnc cutting ie 4x4 sheet of plywood?

You'll want to use a valve and reservoir, so that your compressor doesn't run non stop. You'll want to have full vacuum before you place your part on the table, then open another valve to hold your part.

I think you'll have a hard time with a 4x4 sheet of plywood, because with a venturi system you'll need a perfect seal, and if it's not perfect, you'll lose all your vacuum in about 2-3 seconds.

With a vacuum, the holding force depends on area. A venturi system with a good seal can get you about 10psi of holding force, or about 23,000 lbs of force on a 4x4 sheet. If you can get it sucked down, which I'm not so sure you can.

[teamtexas]

eloid- The venturi uses compressed air from your air compressor to create a vacuum. The 4.2 cubic foot per minute of compressed air will be exhausted as a vacuum is created on the suction side of the device. If you use storage tanks you can get a large reserve to use, but like Gerry said it goes quick if you don't have a good seal. I've never seen a vacuum used to clamp parts, but can't figure out how you don't loose all the vacuum as the bit cuts through the part.

Dan

[ger21]

Dan, you either don't cut through the part, or you keep your "zones" within the part, or make dedicated fixtures.

[teamtexas]

HMPH....I hadn't thought of making dedicated fixtures for my parts. Won't the wife be happy when she see I found a new use for the vacuum former thats collecting dust!

Dan

[Glidergider]

Have you considered getting an old refrigerator compressor? The suction side of the compressor will pull 27 inHg. I just put mine together tonight. I got my compressor for free at the appliance store. When they sell a new frig, they usually pick up the old one. Often the old fridge still works and thus the compressor is available.

I got lucky an scored a compressor within 5 minutes of walking in to their store. I got it for free but gave the service guy $10 to be nice.

[CarlosC]

Is there a site that shows(in excruciating detail) how to disconnect
a refrigerator compressor? And then how to make it into a useful
vacuum pump? I have a an old refrigerator that I have been saving for just such a purpose.

[Glidergider]

CarlosC
Do a Google search on DIY compressor vacuum pump. Yes, there's a site out there. But really it is simple. Don't saw, but rather cut the copper tubes. Sawing copper might induce copper filings into the compressor. I'm sure there are many guys that have sawed theirs off. Make sure you leave the copper at least 5 inches long. In other words, don't cut the copper to short. Remove the power wires (reuse), remove the mounting bolts and your done. If you see a starting relay, or starting capacitor, or overload protection in the power circuit, keep those for reuse. In the picture above, you can see 2 small items which are just that.

Don't lay the pump on its side because it has oil inside that will leak out the copper tubes.
Dave

Edit, Here's a site:
http://www.berkut13.com/sucker.htm