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I just ordered the vacuum bridge clamp from LMI. I need some advice on a vacuum pump now. I have a Venturi pump and large compressor but I would like to buy a dedicated vacuum pump. I was looking at this pump from Harbor Freight (http://www.harborfreight.com/two-stage- ... 66466.html) I have an additional 20% off coupon but want to know if it is adequate to work with the LMI vacuum clamps. Thanks for any advice.

I am using a similar pump and it works fine with my vacuum press and also my LMI bridge vacuum clamp. You should have no problem.

Is it possible to simply screw a vacuum hose to the inlet of a compressor and turn it on? The reverse of a compressor is a vacuum pump.

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No! Most are not designed to be used for that. It has something to do with the valves as it was explained to me.

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More then you will ever need or want to know can be found in the handbooks on the Gast site:
http://www.gastmfg.com/literature_downloads.aspx
HF is always a bit confusing in that their numbers are often skewed from what the higher end manufactures use. That should be an appropriate size, but remember, if you are bagging a project and the thermal protection clicks the pump off, the project may be ruined. What is the elevation of your location in NM? If you are at or above 5000 ft, that pump may barely be enough, at sea level it would be fine.

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Very good information. I appreciate the link to the Gast site. I am between 5000 and 5500 ft above sea level. Had no idea elevation was going to have an effect .

I bought a nice double stage Gast piston type pump as surplus off of Ebay for a good price--it was new, but cheaper than the HF model. I don't remember the exact specs on it, but it pulls fine at 4000 ft elevation. If you keep your eyes open, there are always pretty hefty rotary vein type pumps (as well as smaller piston type pumps like mine) available as surplus on Ebay, and frequently at a good price. The good thing is that you can get the specs off the Gast sight as comfyfoot pointed out.

Dave

Most pumps can pull 25 inches of mercury, (technical details on the Gast site), you lose a unit per 1000 feet of elevation, so if your pump pulls 25 at sea level, yours will pull 20 at 5000, according to the Joe Woodworker site, 19-20 is minimum for vacuum bagging, so whatever pump you get, it will be working to capacity, and therefore may trip the thermal protection, possibly ruining a project.
I just scored a rotary vane Gast off of Craigslist, it is 1/2 hp 7 cfm, so I can empty a large bag quickly, but I will still be working the pump to get the 20+ inches at 3500 in elevation, rotary vane will move more air, but will not create the pressure of the piston or diaphragm pump, so I may need to augment my press with a small piston pump to get the final pressure, I look forward to making the press and finding out, I am planning on making the frame press on Joe's http://www.joewoodworker.com/veneering/ ... -press.htm

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http://www.qualityvak.com/electric.html

I use one of these. Runs off my compressor. Great unit. Good support...in business for a loooong time.

Michael

Thank you guys for the great info. So it seems a Luthier is a mix between Carpenter, Artist, Physicist, Chemist and Engineer. In my case Jack of all trades and Master of none, so far at least.

Hello. I am in the same situation. I have found this cheap pump on Ebay. Will it work with the vacuum bridge clamp from LMI?
Thank you very much,
Carlos

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I have a quality vacuum pump (ped vack), circa 1998 I would like to get into vacuum bag veneering, to laminate backs , sides and tops.Any suggestions for a good source? or should I make my own for luthiery??

Someone around here, maybe Shane, used to talk up using a pump from an old fridge or freezer. They're usually free and run quiet and cool. With the bridge clamp you're hardly pulling any air at all, so you need pressure, but the capacity matters less.

I was about to pull one out of my friend's garage freezer (daughter learning to drive) when another friend ended up with an extra Gast he didn't need, so I don't have first hand knowledge, but one thing I remember, there is oil in the freezer pumps and if you don't put a hose on the exhaust end, you'll spray oil around.

Mike

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Mike Lindstrom

I've been using a small compressor pump out of an old chest freezer for about 6 years now and have been more than happy with it's performance.

The main advantage to these is that they are nearly silent. They are capable of pulling as much vacuum as true vacuum pumps, although the CFM may be a little slower, so you would want to expel as much air out of a bag system as possible before pulling the suction.

I use this pump for gluing braces, bridges, holding the guitars for sanding, cutting binding channels, FP finishing (you don't have to touch the body, so no fingerprints), etc. It's like a free apprentice only silent. <g> I've accidently left mine on for as long as 5 days before noticing it was still on.

If your interested in looking into this kind of system, the Joe Woodworker site has great tutorials and supplies. There also is a thread on the MIMF site on an ingenious system Jason Rogers built for his square footage impaired shop.

I can fish out a picture of my setup if it's of use to you.
Oh, did I mention they are quiet ?

The rotary vane type pumps are really quiet as well, I hope my bargain works out, I just ordered a bunch of stuff from the joewoodworking site to get my frame press going. I am very excited, which is why I am posting, since I have nothing really to add to this thread right now.
Rob

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