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Calling all Vacuum chuckers

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All,
While I need to spend more time turning it is the gagets that we like.... Right! Anyway, I have been considering purchasing a vacuum chuck for the shop. Not sure that I really need one but I thought I would ask a question or two. I have been turning a lot of bowls and starting to get into platters. The first question is who out there is using a vacuum chuck? Second, tell me some pros and cons that you have expereinced with a vacuuum chuck. I have seen them used but I have never used one before. Please share any thoughts concerning this subject. Thanks, Vince
 
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i have the one on bill gumbines site and a gast vacuum pump.

www.wonderfulwood.com, you'll see it there.

it's awesome, no downside, i just love it. there are many ways and actually, my new stubby lathe i am getting in a month or so has a built in vacuum port, but i love my chuck, couldn't be without it.

sascha
 

hockenbery

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Vacuum chucks are great for lot of things. If you have the essential tools I reccomend them.

The pluses:
Easy to work on the bottom of a bowls when finishing.

Since you don't need a place for screws or a tenon for a chuck, using vacuum is the only easy way to rechuck a finished bowl that may need to go back on the lathe.

It only requires a reasonably round surface to grip so it makes an easy way to grip a spherical form.

You can make some simple fixtures to hold things off the lathe as well.

minuses ---
Too much vacuum may crack a bowl or platter. I tested my first system for leaks using one of the indestructable 5 gallon buckets that wouldn't even flex when I stood on it. The vacuum imploded the bucket.

Takes extra time to attach the system an put the vacuum chuck on the lathe and maintain the surface and foam on the chuck.

Need to dedicate a faceplate for each drum chuck you want set up.

Easy to make chucks -- probably another plus.
I make all of my own chucks often from 2 or 3 pieces of construction 2x10 face glued together. I mount these on a faceplate sealing the contact area with hot melt glue and turn a drum chuck and glue thin foam on the contact surface. These tend to leak air through the endgrain and glue joints. So I wrap the outside with duct tape whose true purpose in life is to to seal air leaks.
Conventional thought is to make the drum chuck with a stave construction glue-up to prevent the endgrain air leak. This is way too much work for a woodturner. I also tend to turn my drum chucks for custom fits fairly frequently and and like the fact that the are so easy to make this way.

happy turning,
AL
 
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Be careful

Vince,

Power failures are a vacuum chucker's worst nightmares. If someone trips over a cord and unplugs the vacuum pump, or any other electrical event occurs while a piece is spinning on the lathe, then you have a spinning object with no reason to stay attached to the chuck.

I tend to hurry too much when doing a demo and I reversed a bowl on a vacuum chuck and the bottom was thinner than I realized. You got it, I went through the bottom while cleaning up the inside of the base. All I could do was say, "See what happens when you do something stupid?" as the bowl bounced around the shop. Someone wanted the bowl as is, so I gave it to them. I should have mounted it for show and tell.

Suppose you have three chucks of diameters 2, 4, and 6 inches, and you are going to mount a platter on those chucks using 22 psi. Since the areas exposed to the vacuum are approximately 3.14 sq in, 12.57 sq in, and 28.27 sq in respectively, the corresponding forces will be 69 pounds, 276 pounds, and 622 pounds. Ahah! How many thin platters do you know of that can withstand 622 pounds of force? Think about Al's bucket, which for simplicity we will assume is 12 inches in diameter. The force will be
(3.14)(36)(22) = 2488 pounds. :eek: Now Al probably did not have that much area involved, but it boggles the mind to think of the force when large chucks are used. Just some food for thought. :D :D
This should help you understand the importance of a bleeder valve to control the pressure applied.
 
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Ed,

You forgot to figure in the atmospheric pressure over the area of the side of the bucket. Therefore, for a 12x18 5-gal bucket, add 3.14 x 12 x 18 = 678 sq. in. x 10.22 (PSI at 22" Hg. at sea level pressure of 14psi) = 6,929 pounds of pressure in addition to what's pressing on the end. :D

Bleeder valves are good things
 
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Love mine

I do not know if I could turn without my vacuum chuck system anymore!! It makes life so simple. I made my chucks from a 2 inch thick piece of maple using a 1 x 8tpi nut, weather stripping and schedule 40 pvc fittings. You have to use the high strength epoxy to attach nut and need to coat the full piece of maple with epoxy to stop leakage. I figured up once that my total investment was about $270 including used Gast pump from ebay, rebuild kit for pump, EZ Vac unit from Woodturners, the wood, PVC, glue, nuts etc. This was less than a new Gast pump from any of the suppliers.

Like Mark said - make sure you have a bleeder valve to control the vacuum. Use your tailstock whenever possible for those times you don't use enough vacuum - DAMHIKT!! ;) Once you get used to using the system it takes only seconds to hook up on machine and you will never be without it. I really can't find any downside - just benefits!!!

Wilford
 
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Turn it around!

Mark is absolutely correct. Since Al said that the bucket imploded, I guess that it was the mouth against the chuck, making the total force
6929 + 2488 = 9417 pounds. I guess you can see why that bucket imploded.

The important thing for the novice to understand, if they are not used to dealing with pressure computations, is that as the area exposed increases, the force against the object increases also. If the radius doubles then the force increases by a factor of 4.
 

Steve Worcester

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hockenbery said:
minuses ---

Need to dedicate a faceplate for each drum chuck you want set up.
I used to dedicate a faceplate to each, but a great way around that is to tap MDF and make madf chucks.
Johnny Tolly wrote and article on it that I have posted in the HOW TOO section of my web site
http://www.turningwood.com/howtoo.htm

The cost of a tap to fit your spindle is about the cost of two faceplates sometimes, but it will pay for itself in no time!
 
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Mdf

Steve,

MDF makes great jam chucks, however, when I use it to make vacuum drums, I soak it in shellac, let it dry, and then coat it with epoxy; otherwise it leaks like a pasta drainer.

Mark
 

hockenbery

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Steve,
Soren Berger had a drum chuck he was using at an AAW symposium a few years ago. It had a plastic base that fit a scroll chuck and a pices of pvc pipe that fit snugly in a hole in the plasic the wall of the chuck was just cardboard concrete form (sona tube). The pvc fit tightly enough into the morse taper so that it held vacuum.

I've been meaning to try this sometime. Maybe someone else has. I figure if it works in new Zealand it would work here too.

Ed,
Did you figure in the altitude for Annapolis??
The bucket was held against a disc so it had max pressure.

If the pump is turned off you usually have time to stop the lathe and grab the piece before you loose the vacuum because the system is till closed and if it didn't leak could hold forever. However the best systems leak.

happy turning,
Al
 
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Following The Bouncing Bowl

Before anyone comments that a power failure would stop the lathe at the same time the vacuum quit . . .

I got to play Dodge-The-Flying once. Since I used a used dehumidifier compressor (free from the appliance shop) as my vacuum pump, I didn't know that those things have internal thermal cutouts. So, turn, turn, turn and all of a sudden the bowl launches when the thermal cut in and the compressor just stopped. :eek:

Cure was to use a small fan blowing on the compressor's shell for cooling as would be the case in the dehumidifier housing. When I set up my tandem rig for more cfm to do larger pieces on my big lathe, I used one of the old fans, put the whole rig in a wood box with a filter at one end and the fan at the other. Thing'll now run all day without a hicup. Nice and quiet too. :D

M
 
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I love the vacuum chucking

I have seen many references to using PVC pipe with a padded lip. Since PVC is designed to take pressure and doesn't leak like end grain wood it should work fine. :)

Look out for catches, the tail stock advice is good. I have chased a plate or two across the shop after a good catch and popped the vacuum loose.
 
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Vacuum Pumps on The Cheap

Got several e-mails regarding my post on compressors-as-vacuum pumps, so figured I'd post a pic of how to set these up. These were taken out of used dehumidifiers by an appliance shop who has to recapture the freon before junking the units. The compressors are then trash and most shops will just give them to you provided you take the whole thing to cut down on their trash. You can simply clip the lines and re-work them a bit, attach a power cord and you've got a free vacuum pump. 50-pint size units will tipically move about 2.3 CFM and will pull down to 27" of Hg. without much trouble. You will need rudamentary plumbing and electrical skills and about $20-30 in fittings and parts to get up and running. This picture is of my tandem unit (before it was placed in the box) that I use on my Stubby through a fixed connection. You will need a suction filter since wood dust will kill one of these things pretty quickly, and a vacuum gage ($7) and 1/4" ball-type bleeder valve ($5) are strongly recommended as discussed above. Don't neglect to use a cooling fan as I found out the hard way :eek:

Since the compressors are free I have two more sitting on the shelf in case one or both reach the end of their useful second lives.

I could, of course, just buy a nice Gast pump and forget about the rest, but doing things like this keeps peace with my Scottish ancestors :D :D

Mark
 

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Oil?

Mark,

Nice DIY. One thing that concerns me about using a compressor is that they are made to run with oil in the freon acting as lubricant. I have read of turners squirting oil into the compressors like you do air tools but then you have a problem of atomized oil coming out into the shop with the exhaust air.

On a Gast rotary vane unit the vanes are made of graphite. I always recommend a filter on both inlet and exit of the gast units as you will get a black graphite powder into the shop without a small filter on the exit side of the pump. The rebuild kit for a used Gast Rotary vane includes all new graphite vanes. Being graphite they do wear but are self lubricating and do not need oil.

Wilford
 
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Wilford,

These have an oil bath pan in the bottom of each shell. Company tech even sent me a how-to for changing the oil; haven't done it yet. You can't see it in the picture, but the exhaust from both Units goes into a double condensing coil that drains into a cup, thereby eliminating the oil fog problem. After about 8-12 hours of operation I check the cup for condensate. After 2 years in use, although intermittant at best, I've condensed about a tablespoonfull of oil. I have added a like amount of Select synthetic compressor oil back into the units using the 3rd "process" tube.

In truth, I don't expect these things to be long-lived (After all, it is their life-after-death deal), and I'll probable get a "real" vacuum pump at some point. Thing is that turners on a tight budget (small reserve) can use these to get started with vacuum chuck turning for a very small investment.

Agreed, exhaust filter is required on graphite vane pumps. It also acts as a muffler on other types.

Mark

Mark
 
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pre-filter for vacuum pumps

made a filter from that 4" white plastic sewer pipe - whatever length you can manage, mine was about 16" long, filled with fiberglass insulation and then capped with the same plastic meterial end caps, with holes 31/64" drilled in each cap, the holes will accept a 1/4" barb fitting for hose, seal with silicon. They also act as a bit of a reservoir -in case of power failure. A check valve upstream of the pump can also save some vacuum.
 
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Price

Mark,

Good job on the condensor system for the oil vapor - are you sure that moonshining is not in your background?!! :D

You can find some good Gast rotary vane units on ebay, you just have to be patient and ready to jump when the right unit comes along. I bought mine for $75 with shipping and both inlet and outlet filters. I then contacted Gast and purchased a rebuild kit for about $46 dollars. About $120 total. :cool2: I have not taken the time to rebuild mine but will have to do so shortly as I am seeing some minor drop in vacuum from when I first started using it. About 1 inch - nice thing is with wear it still is steady vacuum just can see it slowly creeping down. As I still have to open the bleeder valve I can run a while without using the rebuild kit. Each rebuild kit is rated to run something like 10,000 hours before it needs done again. I'll be surprised if mine ever needs a second rebuild!! ;)

Wilford
 
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vacuum measurement

Mark Mandell said:
Ed,

You forgot to figure in the atmospheric pressure over the area of the side of the bucket. Therefore, for a 12x18 5-gal bucket, add 3.14 x 12 x 18 = 678 sq. in. x 10.22 (PSI at 22" Hg. at sea level pressure of 14psi) = 6,929 pounds of pressure in addition to what's pressing on the end. :D

Bleeder valves are good things
I,m glad you corrected the conversion of inHg to psi. the max. that can be obtained is 14.7 psi
 
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Great Info on Vacuum Chucking

Thanks Guys for all the info on vacuum chucking. I have been wanting to use this method but wasn't sure where to start. I can't wait to give it a go. great post.
 

Steve Worcester

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Buy the biggest pump you can afford. More CFMs is more important (to woodturners) than inchs/mercury. As long as the pump will pull 22"Hg, you're good.

I bought a big Gast that I use on the lathe and for a vacuum forming machine.
 
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Anything over 15" vacuum will work, but get a Gast constant duty pump (not that high priced at The Surplus Center), use a bleeder ball valve (even Home Depot has them) and take light cuts with no larger than a 3/8" gouge. I've never had any piece implode and never had one fly completely off my lathe. Sometimes they'll loose being centered, but don't come off. I decided to sink money into Oneway aluminum vacuum chucks rather than DYI, and they've also not failed me ever. My home-built setup will pull 20" every time at the spindle according to my fluid-filled vacuum gauge. Different kinds of wood will drop that according to how porous they are. I followed the Ohio Valley Woodturners Guild paper (Vol. 1, Issue 1, Feb. 2004), but put the filter just in front of the pump.
 
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Buy the biggest pump you can afford. More CFMs is more important (to woodturners) than inchs/mercury. As long as the pump will pull 22"Hg, you're good.

I bought a big Gast that I use on the lathe and for a vacuum forming machine.

How about the Venturi system? I was told it works equally well. The compressor doesn't run all the time, it only cycles on & off, and doesn't need a large compressor. Was there any break through in this alternative vacuum system? Has anybody done any side by side comparison on the pros and cons of traditional vacuum pump and Venturi?

In case there is a black out, a compressor with a holding tank should provide enough time to turn the lathe off or the lathe to coast down.

I believe the Venturi has lower CFM, what does that mean in vacuum chucking application?

Gordon
 

Steve Worcester

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I started with a venturi, and they require a bigger compressor than what I had and they are NOISY. The more vacuum you want, the more air they require.

Personally I would say unless you happen to have a large compressor (stand up 60 gallon? IMHO) and someone gives you a venturi, then save the money and buy a used vac pump to start with. Or come up with a 3/4HP motor and buy an old York air conditioning pump out of a car (had one of those at about $40) JB weld the centrifugal clutch on it and attach the motor to it. They are oil reservoir but real work horses and a lot quieter than a venturi.

More cfms means you can work with more porous woods (end grain) and more small voids in the wood as well as recover from a slight catch. You will notice that most have very low CFM at high IN/Hg, but a good rating is usually the HP rating as well. Low HP motor will typically not work well at higher vacuum. While you only need about 10-15 In/Hg for woodturning, the ability to go up mean that more leakage is tolerable and more recoverable.

And put a cleanable filter inline before the vac side of the pump as it will save a lot of wear and tear. And use a tubing that won't collapse under vacuum. Rubber air hose works fine, but not the small diameter coilly stuff.
 
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An inexpensive Vacuum chuck can be made just using a domestic Vacuum.Most pieces I make are held in a vacuum chuck sometime in their making.Once you have one you wonder what you ever did without .'
Go to sawg.or.nz and look at projects under Vacuum chuck and Dick has an article on how to make up the system for under $10.
My latest addition to the system is a promount by woodcut .I know hold work for carving using the face plates I have made for the lathe
timberly@xtra.co.nz if you would like to know more ,Cheers Terry
 
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Vacuum Chucking for Dummies

I ran across this while exploring different options for my lathe. I apologize if it has popped up before, I'm new here and legally blind to boot so I may have missed it but I thought I'd post the link anyway. It is pretty much what I was looking for - a "do this, now do this and BTW here are all the part numbers" kind of thing. There may have been slight price increases because this is from 2006 but I think it covers all the bases on how to do it, at least this particular way. Copy and paste if the link doesn't work.

http://www.midhudsonwoodworkers.org/Jan06_Turn/vaccum_chucks_demo_ebook.pdf

Charles
 
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Steve Worcester

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vacuum chucks

figured out a way to cut leakage. I use a Gast pump and faceplates from Bill Noble. I mounted a piece of wood on the nut faceplate thingy from Bill. then drilled the hole in the center big enough for a piece of PVC that I put inside the chuck. No leaks and no duct tape or coating needed. Use foamy from craft store for the facing. Runs about $1.00 for a 18"x12" piece. I use mine whenever I finish a bowl or plater that needs the bottom finished.
 
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An inexpensive Vacuum chuck can be made just using a domestic Vacuum.Most pieces I make are held in a vacuum chuck sometime in their making.Once you have one you wonder what you ever did without .'
Go to sawg.or.nz and look at projects under Vacuum chuck and Dick has an article on how to make up the system for under $10.
My latest addition to the system is a promount by woodcut .I know hold work for carving using the face plates I have made for the lathe
timberly@xtra.co.nz if you would like to know more ,Cheers Terry

I will trip in here Terry and make a note the link should be .org.

http://www.sawg.org.nz
 
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After trying out a friend's from Bill Gumbine I just ordered the Vacuum master and a Gast Pump. Not cheap, but it's easily shifted from one lathe to another and that can save a lot of money quickly.
 
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I have the Oneway system on a Oneway lathe and am entirely satisfied with it. I don't know if it can be adapted to other lathes.

I sometimes vacuum a reversed bowl to a round wood block on a faceplate that has been cut so the reversed bowl fits on it. The block has a hole drilled in it's center so the vacuum pulls the bowl against it.This seems to work quite well as most of my bowls are turned in at the lip.

Malcolm Smith.
 
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+1 to Terry's tip about using a domestic vac.

Never had any problems. And it's prob. kinder to the Stubby inbuilt port washer than a pump.

You just have to be sure you have enough bleed in the system so the motor doesn't overheat.
 
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