Vacuum pump advice

[Sean Reilly]

hello,
I have finally decided it's time for me to get a vacuum pump, the three reasons I want to use it for are veneer/marquetry, bent lamination work, and as a vacuum chuck for my lathe. I was looking at kits provided by joewoodworker.com and I had a few questions. First) is there any benefit to having an auto-cycle vs. continuous run VP, besides the noise? Also I was looking at getting the Excel 1, it is only rated at 1.1 cfm and for my veneering and lamination work this seems like it will be enough. So my other big question is will this work as a vacuum chuck on my lathe? I don't mind getting the Execl 5 (with 5.5 cfm) if I need it, but most of the time I know I'm not going to need that much power? So was looking for some advice from someone that may be using a vacuum pump as the source of suction for a vacuum chuck.

Thank,

[Bill Adamsen]

Sean:

I just built a slight mod to the JW plan and documented here on the forum. I used a double pole double throw (on/off/on) switch to provide the cycle/continuous. It was a trivial enhancement. Haven't tried to use yet with a vacuum chuck so I can't answer that question (it should by all estimates work). My understanding was that chucking was more related to the vacuum generated (requires 15"hg) than the CFM. There is a page dedicated to this at JW.

If you look at photos of the completed JW units, there are lots of names you'll recognize from the forum. Lots of experience here with vacuum for pressing and other uses (I am using for boat work and yikes ... composites).

[Mike Henderson]

My understanding of doing vacuum chucking on a lathe is that you run the vacuum pump continuously and have a bleeder to control the amount of vacuum on your project - too much vacuum could collapse certain projects.

Joe Woodworker has a lot of information on this on his site. He also has equipment for sale and can give you advice.

Mike

[Bruce Wrenn]

Check out a couple local HVAC places for used units. When they no longer pull in the micron range, they are junk. New and a rebuild are about the same cost, plus with new there is no down time. Over the years, I have gotten several from junk yards. Usually pay less than $10 for a unit.

[Jamie Buxton]

For vacuum chuck advice, try looking and/or posting in the Turning Forum of SMC. I think many turners only watch that forum.

[Tom Hartranft]

My experience is 2 years vacuum pump use for my wood lathe. I got a used Gast 75R645 ... twin cylinder piston pump. Rated for continuous operation at ~5 CFM / max 27" Hg ... http://www.google.com/url?sa=t&rct=j...,d.eXY&cad=rja. When used with a lathe for chuck mounting turning items, one has to deal with both chuck/wood seal leakage and with porous wood leakage. My research prior to getting my Gast pump found turning tool forces would require a minimum of ~15" Hg vacuum (better to have more) to hold the turning item securely.

In the link, look at the lower right corner plot (60 Hz) of CFM vs inches Hg and note that the Gast model 75R delivers 15" Hg at ~2.2 CFM so your chuck/wood seal + porous wood leakage could be up to ~2 CFM and the pump would still deliver the minimum needed 15" Hg. Similarly, the pump would deliver 20" Hg if leakage were reduced to ~1.2 CFM. My pump generally delivers ~ 23-24" Hg which is sufficient to hold my turnings securely for my 'clean-up' work on bowl bottoms using the vac chucks I've made. Not telling you to get this particular pump, but keep the lower right corner pump performance curve in mind when shopping around for a vacuum pump for lathe chucking.

Tom

[Jim Becker]

I picked up a surplus Gast pump that does double duty...both for veneer work and vacuum chucking at the lathe.

[Frank Drew]

Check out a couple local HVAC places for used units.

I agree with Bruce that you could get lucky in the used market; in addition to HVAC companies, also look at used machinery and motor dealers if there are any within driving distance (call first to see what they have.)

[CPeter James]

I have built 6 or 8 of the vacuum chucking systems. I also wrote the following article which you may find helpful. Since I wrote the article, the price of the pumps has gone up a little. The one that I use on my lathes will pull about 25"+hg with a tight grained bowl on the chuck. I am now using yoga mat material for the sealing gasket on the chuck face.

IMG_7647.jpg

IMG_7644.jpg

http://bhillent.com/vacuumchuck2.pdf
CPeter

[David C. Roseman]

For vacuum chuck advice, try looking and/or posting in the Turning Forum of SMC. I think many turners only watch that forum.

+1 on this. Sean, use the SMC search function to search for "vacuum chuck" and you'll find this has been discussed quite a bit.

1.1 cfm is fine for a veneer press but way too low for reliable vacuum chucking on a lathe. While that pump could pull enough hg with a perfect seal, the higher cfm is important to being sure it can handle slight leaks that are inevitable when turning on the lathe (e.g.. porosity and voids in the wood, leaks around the chuck seal). Since you already know about Joe Gorleski (joewoodworker.com and veneersupplies.com), take a look at the reconditioned GD Thomas (Rietschle-Thomas) pumps that he has for $130. Excellent commercial pump that generates 3.15 cfm. Gorleski is a very friendly guy who runs a first rate veneer supply business, and does some vacuum chucking himself. You may have seen from his two sites that he's a good source also for all the specialty fittings, oil-filled vacuum gauge, filters, etc. A couple of years ago I wrote a tutorial on building my vacuum chucking system and integrated handwheel and vacuum adapter for my Grizzly G0733 lathe (which comes without a handwheel). With the pics it's too big a pdf file to post on SMC, but if you're interested in seeing it, PM me and I'll email it to you. Including the DIY chucks, the whole system cost me only around $175 back then. It's well worth building your own.

[David C. Roseman]

I have built 6 or 8 of the vacuum chucking systems. I also wrote the following article which you may find helpful. Since I wrote the article, the price of the pumps has gone up a little. The one that I use on my lathes will pull about 25"+hg with a tight grained bowl on the chuck. I am now using yoga mat material for the sealing gasket on the chuck face.

IMG_7647.jpg

IMG_7644.jpg

http://bhillent.com/vacuumchuck2.pdf
CPeter

CPeter, nicely done.

[Tom Giacomo]

A 1.1 cfm is too low for vacuum chucking.

[Andy Pratt]

seconding that comment, I have a 1 cfm and it works great for veneer pressing but I can't imagine it doing bent laminations or vacuum chucking, make sure you get enough pump if you want to do those things