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travisc
10-26-2007, 12:35 PM
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
10-26-2007, 01:43 PM
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
10-26-2007, 08:57 PM
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
10-26-2007, 09:50 PM
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
10-26-2007, 09:57 PM
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
10-26-2007, 10:02 PM
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
10-26-2007, 10:33 PM
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
10-26-2007, 11:08 PM
Dan, you either don't cut through the part, or you keep your "zones" within the part, or make dedicated fixtures.

teamtexas
10-27-2007, 12:17 AM
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
10-27-2007, 01:52 AM
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
10-27-2007, 06:26 AM
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
10-27-2007, 08:55 AM
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

turpija
10-27-2007, 02:32 PM
I just have old refrigerator which i've scavanged for compressor, and it's pretty simple, connect it on power and one tube will blow air, other one will suck ...
then, grab a plastic bottle and connect it on vacuum side ... this is what happen ...

http://www.youtube.com/watch?v=tCPREBUFqlo

... but if you some serious fun then connect it on blow side .... and here you go ;)

http://www.youtube.com/watch?v=4pR_Fngd_5Y

PS don't have a vacuum pressure gauge to tell how much it actually "suck" but i would recon - decently.

Glidergider
10-27-2007, 07:57 PM
turpija
Awesome video. It really shows the power of one of these refrig compressors.
Thanks.
Dave

eloid
10-29-2007, 07:31 PM
I was thinling about making a small vac grid like the below links
for my 4x8 sheet but using small pucks


http://www.nemi.com/grid_table_fixturing.htm
http://www.nemi.com/vacuum%20grid%20table.htm
http://www.shopbottools.com/Brady%27s_tricks.htm


another link
Venturi Based Model vaccum

eloid
02-06-2008, 08:33 PM
Question is there much oil in the fridge compressors?
I got one bet seams like there no oil? can u add oil?