Official Luthiers Forum!

Hello,
I am starting my search for a vacuum pump for my fixtures. I am curious what brand, and models being used. Any pics and specs would be appreciated. Also if you use a reservoir or not. My fixtures will hold electric violin and guitar bodies, with the tops being approx .21 thick at the end. All parts will have a few 1/8th holes for index pins to help out. I am curious what you have found that works for your particular application. Also, has anyone used a regenerative blower (overkill?)?
Thanks for the info
Evan

In my machine I'm using a Venturi I got a long time ago; it'll pull 26 or 27mmHg at something like 4-5CFM. It's slightly overkill, but I like the security in being able to hold down a piece that might have a pinhole or a hairline leak. If I were buying a Venturi now, I'd get it from Vaccon as I've found their product and prices to be best (and my other Venturis are from them).

If you're holding one component at a time, and you're not cutting really aggressively, then you can get by with almost any pump. Regenerative blower is definitely overkill. I remember talking to John Watkins awhile back and he mentioned having a 'big' vacuum pump (40HP or something) but that he used a Venturi because there's no advantage to a big pump when you're holding small well-sealed workpieces.

I have a small mechanical medical vacuum pump that I use for testing fixtures before I send them to clients as it has very low flow and has vacuum adjustable down to almost nil, and it will work for holding stuff down in the machine, but if there's a leak anywhere in the system then its seal pops instantly.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Go here:

http://www.mcmaster.com/#catalog/116/344/=923sw9

And find this product I.D.

41605K14

This is a commonly used venturi pump that will function well in any capacity used for luthierie. It runs off compressed air and has no moving parts so it lasts forever. Unless your compressor is only the smallest pancake type compressor, the airflow will not be enough to seriously impact the on-off cycles of the compressor.

I use this model for many hours on end. With a pressure regulator and a vacuum gauge, you can dial in any amount of vacuum needed up to the maximum.

I've seen some pretty elaborate setups by some luthiers to achieve vacuum. I honestly don't understand why any application of vacuum used for any task a luthier does requires any more complexity than a venturi pump. If your compressor has less than a 20 gallon tank....then maybe a seperate unit makes sense. If your compressor has a 40+ gallon tank there is no reason to get anything more than this.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Hello,
Thanks for the replies. I have looked at the venturi idea and after looking at all the different setups, it just seemed easier to buy a pump. However if the simple ones work, that is great. My compressor is a dewalt, with a 15 gallon tank. It is smaller, but it goes to 200 psi with 5.4 cfm at 90 psi.

Bob,
which model Vaccon do you use (or would you buy if you were buying one)?

Stuart,
Would you be able to post a pic of your setup?

Thanks again for the info,
Evan

Ok you two venturi gurus..... How do you deal with the noise? I have about 4-5 brand new venturi pumps that I have never used due to the noise, and yes, they do have mufflers. They just don't work.

Mike

Mike: Two stage silencer. Check out the hybrid ones they show. They're much quieter than the straight-throughs (though I use a big straight through and don't mind the little noise it makes).

Evan: A JS90 or a JS100, depending on how certain you were of your fixtures. I'd use a JS-60 on my current fixtures, but that wouldn't have worked on the fixtures I used earlier on. I should really get one, actually, since I'm using 4X the air with my current Venturi...

Get the hybrid silencer if you're worried about noise, though if you're using a router in your CNC then you probably won't hear much

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Refridgeration compressor...I will say it again...REFRIDGERATION COMPRESSOR. I just don't get it, this topic comes up all the time and people just want to spend lots of money on "special" pumps for vacuum. The pumps that I have used never have pulled the full 28" that my REFRIDGERATION COMPRESSORS have pulled. Two added benefits of these compressors, they are free (or nearly so, check with your appliance repair guy) and QUIET! Under full vacuum they are under no load so last a very long time and they are nearly silent. But hey....if you think spending money makes more sense you can do it!

Ok...stepping off the box and going away now!

Shane

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Canada

Hey Shane,

I already have a vac but if I ever need another, I will take your advise. I mean I don't want you to blow a gasket, or would that be vacuum gasket?

Got the package! Still haven't had time to take you a pic of why I was interested in resawing!

Mike

So the problem with many of these systems is as stated, they need to keep running....and if you do not have a large air compressor, the system might cycle quickly...

Have a look at this....

http://www.joewoodworker.com/docs/ProjectEVS.pdf

It has gotten some great reviews, and can be build relatively cheap....I would also Imagine that by increasing the reservoir size, it can be made even larger.....

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-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

I built one of these and it works well. Good supplier, too- buying the brass fittings from him was a lot less work than sourcing locally and a lot cheaper as well. With a decent vacuum bag the pump hardly runs at all (perhaps 5% of the time ??).

Running a compressor and venturi seems a bit wasteful to me, but I don't have a big compressor with spare capacity.

I didn't know that appliance repair guys were still pulling working compressors out of refrigerators. Some things never change.

Cheers
John

The only problem with the Joe Woodworker is,for the cost of the PVC Fittings, you can buy a 5 gallon air tank from HB $20. as well as a venturi for Auto AC for about $7. I made mine for less than $200 and that included a 54" x36" VacBag that was $89 from Woodcraft. A few ball valves and a Vac gauge from the local hardware store with some brass fittings. I was in business.

MK

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I'm outside looking in, just farther from the window than most.

Sounds good!

You forgot to add the cost of the compressor...and the earmuffs to drown out the venturi sound...

The economy of a Venturi depends what you're doing with it. Venturis move a lot of air and achieve a vacuum really quickly from a standing start, which means they can tolerate leaks, porous workpieces, and difficult to gasket parts very well. If you have a compressor already, then the cost is much cheaper VS an equivalent mechanical pump ($400-500 IIRC). I've seen some parts thrown against the window of the Fadal during tests of a low-flow vac pump when there were pinholes or hairlines uncovered, if a part chipped near the gasket, etc...and I wouldn't want to catch one in the teeth on a non-enclosed machine!

For vacuum bagging, I always use the mechanical pump.

Something I am really interested in, if anyone has links, are the evacuation curves (CFM vs pressure) for mechanical pumps. There's a big difference between 4CFM @ atmospheric and 4CFM @ 15mmHg. I know Vaccon publishes exactly how long their Venturis will take to evacuate 1CF to different vacuum levels, as well as CFM at different pressures, but I'm not sure how mechanical pumps compare either way. If I find out that a mechanical 4CFM will out-evacuate my Venturi then I might be in the market!

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

We use venturis, an ultra high vac lab pump, and a Becker high volume rotary vane. If you have aluminum fixtures your losses will only be through the wood part. Angled headstocks in particular leak a lot of air through the grain if there isn't a veneer on the face.

If you use wood or mdf fixtures you'll need higher volume capacity. Sealing fixtures doesn't seem to work for me due to the fact that it usually takes me 2 or 3 revisions to get the fixture to where I'm happy with it. By that time it's got vacuum tape and pins in it so a 1.5 hp Becker rotary vane off of ebay for $90 is just the ticket. It's relatively quiet and ignores small losses.

Hi Guys

Thought i would let you know what pumps i use in my workshop.

I am based in South Africa and use a biesse rover cnc ,a machine that runs a Becker pump on it, i dont know if they are available over there, but my machine originally comes from Italy, so i expect that they are available world wide.

I also have a vacuum forming machine that i built myself, for wrapping of PVC to kitchen doors etc, and i found a Milkwrite pump that my father in law did not use any more, originally for milking cows with so theres another pump that could be used.

Both pumps run with motors not air supply, and the becker defiantly is the quieter one.

regards

Jeremy
http://www.budgens.co.za

Oh ya, one more benefit of refrigeration compressors, when you loose electrical power you don't instantly loose vacuum. So if you have a jig for holding the guitar like the one I have below and the power goes out or a circuit breaker blows your box does not end up on the floor. I use these pumps for my CNC fixtures and for all of my guitar related vacuum devices.







Shane

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Canada

Benefit VS what? My little mechanical pump will drop a part a few seconds or less after it's turned off depending on the seal quality and my Venturi will run for 10-30 minutes after the power goes out depending on how full my tanks were. Is there some difference between those compressor pumps and other mechanical vacuum pumps?

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

The benefit is that I don't need tanks. The compressor will hold vacuum when it is turned off. I have tanks on two of the systems I have but don't use them anymore, the vacuum pulls just fine without all of that. Certainly if I needed to evacuate a large area in a hurry I would use the tanks (they are plumbed in but have bypass valves) but I haven't seen a need yet. So, that is an added safety feature in my books. And HEY, are you calling me out Bob!?

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Canada

My mama taught me to never call out a man who's handy with a chainsaw...

I was actually just wondering if the other mechanical pumps drop vacuum right away / which types do and don't.

The Venturi sort of has both options; if I use a manual switch or a normally-open solenoid then it'll just run down the air in the tank if the power goes off. If I use a normally off solenoid valve then it'll instantly release the vacuum when the power goes off (which is why I normally use one of those in production).

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Hello to all,
I decided to go with the venturi out of Mcmaster, as recommended by Zlurgh. I looked at the vaccon product(thanks for the recommendation Bob), and it seemed to have similar specs. In the end I chose the one from mcmaster carr because it was a bit cheaper then the similar vaccon product, and I could get it in a day as opposed to a week. The sound level specs are 7 db higher then the equivalent vaccon with the hybrid silencer (65 vs 58). As a side note, I did an online chat with vaccon, and they recomended the dirt tolerant pump, model vdf 150 st4. It was also a bit more expensive. The venturi showed up today, it is made by Gast, model number vg-015-00-00. I have to get a few fittings and I will give it a try on a few old fixtures I have, and let everyone know how it goes.

Thanks to everyone for the info they provided.
Evan

The dirt tolerant ones are a really cool design, but machinig guitar parts has your Venturi sucking a lot less dust in than most woodworking done with vacuum.

I think I've had junk stuck in mine a grand total of twice ever. It still worked, but the flow was reduced quite a bit. You can just plug the inlet and spray some air in the exhaust to unclog and/or clean them.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Bob,

I was funnin' with ya! (I know you know that but others may not!). Anyway, the small vacuum pumps that LMI and the like sell and that you can find in government auctions and stuff (Gast's etc.) all drop vacuum as soon as they are turned off. The beauty of that is you can switch it off and the piece releases but if it is inadvertently switched off it can leave you buggered as well. With the compressors they hold the vacuum, even when not running. To release your part you need to release the vacuum with a valve. I guess this is just one of those topics where I see people thinking that these compressors are a poor mans option. I think you know that I am not afraid to spend money but I just can't see a better option than these things.

Anyway, it looks like Evan is set.

Thanks man

Shane

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Canada

Excited by the idea of using a refrigeration compressor for clamping/work holding... anyone know if the compressor from a window a/c unit might be suitable for this purpose? Thanks to all for this fantastic informational resource!

Don

I have been offered a free domestic fridge freezer but didn't really want/need it until I read this topic!
So my question is........ will the compressor from a small domestic fridge freezer be adequate for a hobby builder, or should I look for a larger compressor from say a large chest freezer?

Bob.

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http://www.bobmatthewsguitars.co.uk

The first one I have is from your common house refrigerator. I have others that are a step above that were given to me so I am using them but my first was MORE than adequate. All I can say is if it is free, try it!

Shane

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Canada