Vacuum chuck

[Emiliano Achaval]

I’m fairly new at using a vacuum chuck. I bought over a year ago the Frugal vacuum chuck complete system. I love it, don’t know why I waited so long... I have been using the standard that comes with it, 4.5 in chuck. I also bought everything to make 2 more. Today, with Wayne Omura’s help i made a 3 inch one. I can make one more, but not sure what size... I’m thinking a 6 or 8 in? Of course, my new chuck is made with some curly Koa... Thanks in advance for the help...

 

[Gerald Lawrence]

You will find that having extensions will also help for deep or odd shaped vessels which otherwise will hit the headstock. You can do this with reducers from the 3 or 4 . Also when you use the adapter tape the joints to reduce vacum loss. Remember the larger the chuck the more pressure you are exerting on the vessel, So with thin bottoms be careful not to suck it into the chuck and don't ask me how I know this. Also with the filter get an extra at auto parts so when it clogs you will have extra. Dust will get to it thru leakage in porous wood . I have found that the craft foam at craft stores is easier than the tape on method he suggests. Oh by the way for the question 6 should be enough since I do not think you do Mahoney size platters.

 

[Bill Boehme]

...... Of course, my new chuck is made with some curly Koa....

Well, mine is made with curly MDF



I have intended to make a couple more, but so far, this one has been sufficient. It's about five inches diameter.

 

[Emiliano Achaval]

You will find that having extensions will also help for deep or odd shaped vessels which otherwise will hit the headstock. You can do this with reducers from the 3 or 4 . Also when you use the adapter tape the joints to reduce vacum loss. Remember the larger the chuck the more pressure you are exerting on the vessel, So with thin bottoms be careful not to suck it into the chuck and don't ask me how I know this. Also with the filter get an extra at auto parts so when it clogs you will have extra. Dust will get to it thru leakage in porous wood . I have found that the craft foam at craft stores is easier than the tape on method he suggests. Oh by the way for the question 6 should be enough since I do not think you do Mahoney size platters.

I do go Mahoney size often, but I dont know if I can trust a vacuum chuck on a big Calabash, I will try an extension, so far my big ones touched the headstock so I couldn't use it. I'm guessing I missed school the day they had the physics of vacuum chucking, lol. I didnt know adding an extension will create more pressure... I was looking at catalogues, seems like 8 inch is the biggest available. I think you are right, a 6 inch should be just what I need... Thank you Gerald!

 

[Emiliano Achaval]

Well, mine is made with curly MDF

View attachment 24404

I have intended to make a couple more, but so far, this one has been sufficient. It's about five inches diameter.

Beautiful MDF bill! lol I know why you haven't made another one, I have the 4.5 in and its pretty much an all around chuck. I needed a small one for smaller work... Since I have everything to make one more, I want to make sure I make the best size possible to compliment what I have... Aloha

 

[AlanZ]

I use the stainless steel adapter made by JT Turning tools, and use various sizes of spalted PVC pipe couplers to reach the final diameter. Spalted PVC grows locally, I'd have to import curly PVC.

 

[William Rogers]

I'm guessing I missed school the day they had the physics of vacuum chucking, lol. I didnt know adding an extension will create more pressure...

Emiliano, the larger the "diameter", not length will create more holding pressure. Doesn't matter on how long it is. Also make sure you seal the wood you are using for your chuck to reduce leakage in the system. Woods that are very porous (depending on size) I will wrap with shrink wrap or use masking tape.

 

[hockenbery]

A handy one to have is an 8” diameter made with cardboard tubing. Fabric rolls or concrete forms.
This material is stiff but flexible to conform to the outside of an not quite round bowl.

This will hold a bowl for working on the inside.
I also make lots of chucks from wood. Duct tape the outside fun foam on the rims.
I turn them to fit special projects. These are semi disposable and get repurposed

There is a trade off with tube materials
Stiff material -solid turning - no movement to conform to out of round
Flexible material - spongy feel to turning - some conformance to ou if round

Same for foam materials
Thin foam is stiff
thick foam is spongy conforms to slightly out of round work

 

[john lucas]

I use PVC pipe reducers for my larger chucks. That way you get the large outer face diameter but smaller size to fit the adaptors you make to fit the lathe. The best chuck I have was made from plastic decking material. I flattened one surface and glued 2 together to get the thickness needed. then I tapped the plastic 1 1/4x 8. No metal faceplate needed. Wooden adaptors often need to be sealed really well to keep the vacuum from leaking through the pores. I don't know how big your calabash bowls are but a 6 or 8" vacuum chuck will hold them easily. I have an 8" flat one that I use for platters but have to open my bleeder valve to about 15" of vacuum to keep from sucking the center of the platters in. I believe I could implode on at full vacuum. I also have a 4" chuck that is 6" long to work with bowls that are deeper and have rough edges.

 

[Tom Gall]

View attachment 24403 I’m fairly new at using a vacuum chuck. I bought over a year ago the Frugal vacuum chuck complete system. I love it, don’t know why I waited so long... I have been using the standard that comes with it, 4.5 in chuck. I also bought everything to make 2 more. Today, with Wayne Omura’s help i made a 3 inch one. I can make one more, but not sure what size... I’m thinking a 6 or 8 in? Of course, my new chuck is made with some curly Koa... Thanks in advance for the help...

Emiliano, I would recommend adding a hemispherical piece to the outer edge of your PVC pipe chucks. This could be anywhere from ½” to 1”+ wide which gives you a wider variable surface area that is easier to attach your foam to, and gives you the option to use either the outer surface mounting or the inner surface for special uses such as repairs or for holding spheres.

These can be made using the usual suspects (MDF, wood, etc.) but I prefer using non-porous PVC Foam Board. In fact, I have been using this material in place of wood in all my newest chucks (I’ve been using vacuum chucking for 24 years now). It can be glued with PVC cement (but you have to work quickly) or with epoxy or CA glue (med. or thick). This material can probably be found from many sources but I get mine through Pierce-Ohio Co.
http://freckleface.com/shopsite_sc/store/html/product848.html

Turn a groove (1/4”–1/2” deep should be fine) to fit your PVC pipe/tubing. Glue to your PVC pipe and then mount your chuck on the lathe and turn a hemispherical shape (or whatever specialized shape you might need). If you use the Foam Board no further sealing is necessary. But if your piece has any irregular surfaces and doesn’t seal perfectly just insert a piece of packaging foam (with a hole in it of course) to compensate. You can also do this to protect a finished surface.

 

[Bill Boehme]

.... I'm guessing I missed school the day they had the physics of vacuum chucking, lol....

Maybe it wasn't you who skipped class that day. Something that is often misstated is the difference between pressure and force. If a vacuum pump is creating a relative vacuum of 26 inches of mercury (or -12.8 PSIG ... guage pressure is the difference between the contained pressure or vacuum and the ambient pressure) then that is the pressure (or vacuum) regardless of the diameter (or length) of a vacuum chuck. However, the total force exerted on the piece being vacuum chucked depends on the effective inside diameter of the chuck.

For example, if a vacuum chuck has an effective inside diameter of 3" then the area is about 7 square inches and the force pulling the piece against the chuck is 90 pounds (12.8 X 7). If we double the chuck inside diameter to 6", then the area would be 28.3 square inches and the force pulling the piece against the chuck would be 362 pounds. Suppose that we decide that we really need a vacuum chuck with an inside mouth diameter of 8" ... this would give us an area of 50.3 square inches and if we decided to have the vacuum pump pull 26 inches of mercury (the typical sea level limit for a dry rotary vane vacuum pump) then the force pulling (or really the atmosphere pushing) on the piece being chucked would be 643 pounds. It doesn't take a lot of imagination to suspect what might happen if the piece isn't very thick. The moral of the story is to monitor how much vacuum we are applying especially with large vacuum chucks. Also, use the tailstock until you get to the tiny nub .... and use light tool force .... in other words, may the force not be with you.

 

[john lucas]

I do an unscientific test. I put a good solid piece of wood on my chucks of various sizes and pull on it. Make sure nothing is behind you when you do this test because when it releases it does so really quick and you could hurt your self. You find out pretty quickly that a 3" chuck doesn't have a lot of holding power. When I use the 8" chuck I typically bleed off a lot vacuum so that it won't crush the piece. How much? Well I just put a scrap on and tried it at different settings. Usually use about half what my maximum is and on my vacuum system that's about 23" of mercury. Even though I'm pretty comfortable at the settings I use I still use the tailstock until that last minute if I can.
I talked to Nick Cook the other day about turning platters and he turned 3200 in just a little over 2 months for a client. He had 2 lathes set up with vacuum chucks which made production much faster. (still would have take me about half a year I think) So vacuum chucks can really save time.

 

[Gerald Lawrence]

I do go Mahoney size often, but I dont know if I can trust a vacuum chuck on a big Calabash, I will try an extension, so far my big ones touched the headstock so I couldn't use it. I'm guessing I missed school the day they had the physics of vacuum chucking, lol. I didnt know adding an extension will create more pressure... I was looking at catalogues, seems like 8 inch is the biggest available. I think you are right, a 6 inch should be just what I need... Thank you Gerald!

Mahoney did say that at home he uses vacum chuck but did not elaborate on size.

 

[Emiliano Achaval]

I do an unscientific test. I put a good solid piece of wood on my chucks of various sizes and pull on it. Make sure nothing is behind you when you do this test because when it releases it does so really quick and you could hurt your self. You find out pretty quickly that a 3" chuck doesn't have a lot of holding power. When I use the 8" chuck I typically bleed off a lot vacuum so that it won't crush the piece. How much? Well I just put a scrap on and tried it at different settings. Usually use about half what my maximum is and on my vacuum system that's about 23" of mercury. Even though I'm pretty comfortable at the settings I use I still use the tailstock until that last minute if I can.
I talked to Nick Cook the other day about turning platters and he turned 3200 in just a little over 2 months for a client. He had 2 lathes set up with vacuum chucks which made production much faster. (still would have take me about half a year I think) So vacuum chucks can really save time.

Holy smokes! Thats 53 bowls a day! 26 on each lathe! I'm no doubting the story, but thats almost hard to believe!! LOL I have done the test you are talking, with my 4.5 in chuck. I have not been able to even move it yet alone pull it off. I have to try it with the 3 in. SO, John, should I go with the 6 or 8 in? Hmmmm Thank you and Aloha.

 

[Emiliano Achaval]

I use the stainless steel adapter made by JT Turning tools, and use various sizes of spalted PVC pipe couplers to reach the final diameter. Spalted PVC grows locally, I'd have to import curly PVC.

On my next one I will use spalted PVC. Just wait and see! lol

 

[Emiliano Achaval]

Emiliano, the larger the "diameter", not length will create more holding pressure. Doesn't matter on how long it is. Also make sure you seal the wood you are using for your chuck to reduce leakage in the system. Woods that are very porous (depending on size) I will wrap with shrink wrap or use masking tape.

Today I was testing the 3 in one with a piece of white algarrobo known locally as kiawe, the densest wood around here, good enough to chase threads. I couldn't believe it that it was leaking thru the endgrain!! The piece like inc and a half thick, yet you could feel the suction. Amazing power... Thanks for the explanation. Aloha

 

[Emiliano Achaval]

I use PVC pipe reducers for my larger chucks. That way you get the large outer face diameter but smaller size to fit the adaptors you make to fit the lathe. The best chuck I have was made from plastic decking material. I flattened one surface and glued 2 together to get the thickness needed. then I tapped the plastic 1 1/4x 8. No metal faceplate needed. Wooden adaptors often need to be sealed really well to keep the vacuum from leaking through the pores. I don't know how big your calabash bowls are but a 6 or 8" vacuum chuck will hold them easily. I have an 8" flat one that I use for platters but have to open my bleeder valve to about 15" of vacuum to keep from sucking the center of the platters in. I believe I could implode on at full vacuum. I also have a 4" chuck that is 6" long to work with bowls that are deeper and have rough edges.

Ok, I see it here, I think I should go with an 8 inch one for the big calabashes. Today I finished and sold a 16.5 in wide one, by about 15 tall...

 

[Emiliano Achaval]

Emiliano, I would recommend adding a hemispherical piece to the outer edge of your PVC pipe chucks. This could be anywhere from ½” to 1”+ wide which gives you a wider variable surface area that is easier to attach your foam to, and gives you the option to use either the outer surface mounting or the inner surface for special uses such as repairs or for holding spheres.

These can be made using the usual suspects (MDF, wood, etc.) but I prefer using non-porous PVC Foam Board. In fact, I have been using this material in place of wood in all my newest chucks (I’ve been using vacuum chucking for 24 years now). It can be glued with PVC cement (but you have to work quickly) or with epoxy or CA glue (med. or thick). This material can probably be found from many sources but I get mine through Pierce-Ohio Co.
http://freckleface.com/shopsite_sc/store/html/product848.html

Turn a groove (1/4”–1/2” deep should be fine) to fit your PVC pipe/tubing. Glue to your PVC pipe and then mount your chuck on the lathe and turn a hemispherical shape (or whatever specialized shape you might need). If you use the Foam Board no further sealing is necessary. But if your piece has any irregular surfaces and doesn’t seal perfectly just insert a piece of packaging foam (with a hole in it of course) to compensate. You can also do this to protect a finished surface.

Tom, thank you for your help. Could I bother you asking for a picture of one of your chucks with the extra piece you mentioned? I appreciate your help. Thank you and Aloha.

 

[Emiliano Achaval]

Maybe it wasn't you who skipped class that day. Something that is often misstated is the difference between pressure and force. If a vacuum pump is creating a relative vacuum of 26 inches of mercury (or -12.8 PSIG ... guage pressure is the difference between the contained pressure or vacuum and the ambient pressure) then that is the pressure (or vacuum) regardless of the diameter (or length) of a vacuum chuck. However, the total force exerted on the piece being vacuum chucked depends on the effective inside diameter of the chuck.

For example, if a vacuum chuck has an effective inside diameter of 3" then the area is about 7 square inches and the force pulling the piece against the chuck is 90 pounds (12.8 X 7). If we double the chuck inside diameter to 6", then the area would be 28.3 square inches and the force pulling the piece against the chuck would be 362 pounds. Suppose that we decide that we really need a vacuum chuck with an inside mouth diameter of 8" ... this would give us an area of 50.3 square inches and if we decided to have the vacuum pump pull 26 inches of mercury (the typical sea level limit for a dry rotary vane vacuum pump) then the force pulling (or really the atmosphere pushing) on the piece being chucked would be 643 pounds. It doesn't take a lot of imagination to suspect what might happen if the piece isn't very thick. The moral of the story is to monitor how much vacuum we are applying especially with large vacuum chucks. Also, use the tailstock until you get to the tiny nub .... and use light tool force .... in other words, may the force not be with you.

Excellent and very easy to understand explanation! Thank you for taking the time to answer. I greatly appreciate the help. Thats a lot of force on a big chuck!! Amazing... Aloha!

 

[Dwight R Rutherford]

Here is a handy chart I use to gauge the force exerted by my vacuum chucks.

 

[Glenn Lefley]

That is really good to know Dwight. I am getting a vaccum Chuck. (The last component I need for my system ) and I would have turned it on max to hold not considering diameter. Suck the finish right off the bowl !!!

 

[Emiliano Achaval]

View attachment 24414 Here is a handy chart I use to gauge the force exerted by my vacuum chucks.

Wow!definitely an eye opener!

 

[Emiliano Achaval]

Went to the irrigation shop in town today. Not sure why, they have odd sizes, but they have quality stuff there. I decided to go with a 7 inch pic sleeve. The 8 was bigger than 8, and too big. I have found a compromise between 6 and 8 , lol. Because I experienced some vacuum loss thru the test wood yesterday, I decide to apply a coat of marine epoxy to seal this one. Of, course, I made it out of Koa. I will finish it tomorrow.

 

[Emiliano Achaval]

That is really good to know Dwight. I am getting a vaccum Chuck. (The last component I need for my system ) and I would have turned it on max to hold not considering diameter. Suck the finish right off the bowl !!!

Its incredible what you can learn here, one of the most useful resources for a woodturner.

 

[Emiliano Achaval]

View attachment 24414 Here is a handy chart I use to gauge the force exerted by my vacuum chucks.

I wonder what pressure should I use on a big bowl, say around 15 inches wide, with my soon to be latest 7 in chuck? I have been going full throttle with the smaller chucks. Maybe around 10-12?

 

[john lucas]

If the walls are thick you can easily use as much as you want. It's when bowls and platter get thin that the risk is there.

 

[Bernie Hrytzak]

I wonder what pressure should I use on a big bowl, say around 15 inches wide, with my soon to be latest 7 in chuck? I have been going full throttle with the smaller chucks. Maybe around 10-12?

Put your hand or finger in the center of the bowl (or platter)and adjust the vacuum slowly, if you feel the wood moving slightly, you-ve reached the maximum you should apply. Of course if there are micro-cracks or ring shake in the wood, that will be a risk also.

 

[hockenbery]

I wonder what pressure should I use on a big bowl, say around 15 inches wide, with my soon to be latest 7 in chuck? I have been going full throttle with the smaller chucks. Maybe around 10-12?

I do something similar to Bernie but visually. I center the bowls using the tailstock then close the bleed valve until the bowl pulls away from the tail center about a 1/16 to an 1/8 inch.

 

[Mark Wollschlager]

On some porous woods like Oak I put some blue painters tape over the areas I am not turning. The outside of the bowl, if I am finishing the bottom.
That seems to allow me enough suction to complete the job.
In addition I find that sanding dust will block the pores and improve the suction.
Unfortunately that also means that I need to blow the surface, and perhaps through the wood with compressed air to remove the dust when I am through.

 

[Tom Gall]

Tom, thank you for your help. Could I bother you asking for a picture of one of your chucks with the extra piece you mentioned? I appreciate your help. Thank you and Aloha.

I'm not very good when it comes to pictures & computers and sizing and all that stuff. I don't have one of those smart-phones to make things easy. I think (???) I know how to email you some photos....but first I'll have to take the photos, remove the memory card, install it on my computer and download them to my Photos (iMac) then attach them to an email. Is that the correct procedure? Give me a day or two.

 

[john lucas]

Mark I have used stretch wrap on the outside of porous bowls to make the vacuum seal. Much faster than tape.

 

[Tom Gall]

I wonder what pressure should I use on a big bowl, say around 15 inches wide, with my soon to be latest 7 in chuck? I have been going full throttle with the smaller chucks. Maybe around 10-12?

Most likely full vacuum will be fine. I assume you have a regulator or bleed valve installed, so open it up and mount your piece then slowly close the valve to find the optimum vacuum for your piece (thinness, porousness, etc.). If you have flat-rimmed bowls / boxes, etc., I would recommend using a flat disc or plate typed chuck (I don't really know what to call them) covered with neoprene or some other type of seal. This will increase the surface area (depending on the size of the bowl) tremendously.....be careful of implosions! These are easier to make than drum / pipe type chucks and are very versatile. You can even do off-center work with these.

 

[Bill Boehme]

I wonder what pressure should I use on a big bowl, say around 15 inches wide, with my soon to be latest 7 in chuck? I have been going full throttle with the smaller chucks. Maybe around 10-12?

The diameter of the bowl isn't the main factor in deciding how much vacuum to apply ... although it would be one consideration in deciding which vacuum chuck to use. The more important things are the diameter of the chuck and the thickness of the wood.

The graph that Dwight posted helps to answer your question of how many pounds of force do you think would be about right to hold a bowl in place. If we know how many pounds of force then the the graph will tell us how much vacuum to apply. As woodturners, measuring isn't something that we normally do although we have a gut feeling of how much force probably isn't enough and how much force is liable to damage the bowl. Some of this "gut feeling" is learned through experience ... like seeing a turning bouncing across the room.

In actual practice you quickly develop an intuitive feel for setting the vacuum level. You will know which softer woods are easily bruised by too much vacuum, which species leak like a sieve, thin pieces require very little vacuum, keep the tailstock in place, take very light cuts, etc.

I'm not very good when it comes to pictures & computers and sizing and all that stuff. I don't have one of those smart-phones to make things easy. I think (???) I know how to email you some photos....but first I'll have to take the photos, remove the memory card, install it on my computer and download them to my Photos (iMac) then attach them to an email. Is that the correct procedure? Give me a day or two.

I hardly ever remove the cards from my cameras. Instead I use the USB cables that come with the cameras. Cameras also come with software on a CD. If you install it on your computer it will automatically download the pictures when you connect the USB cable. This is quicker and easier than taking the memory card out of the camera and plugging it into the computer. It also is less wear and tear on the memory card and connectors.

You can either attach or embed photos in an email, but that's as much work as attaching or embedding a photo in a post on the forum. I probably ought to post a thread on doing that in the FAQ section.

 

[William Rogers]

When I was first setting up my new lathe, to save time I ordered the Oneway 3-1/2" vacuum chuck. I have to say I really like that chuck. I like the way it is rounded over on the ends. I previously had a homemade PVC vacuum chuck. I had been reluctant to make a 4" one out of PVC until I saw Tom's foam board suggestion. I thought of using casting resin to create the rounded edge.

 

[Bob Sheppard]

Emiliano-
I just recently got my vacuum system working. For the 3" and 4" PVC couplings, I got the Rubber Chucky gaskets. They seem to work and fit quite well.
And I'm jealous that you've got enough koa to use like that.

 

[Larry Copas]

A couple of my wood chucks. Hard maple with vinyl shelf paper contacted cemented on for the seal. I usually make the big ones segmented. Bought a used but re-sharpened tap off ebay for a few dollars to thread the chucks. After threading I soak the threads in ca and re-thread so they last a long time. On the small one you can see I made a seat for the chuck to run true on the spindle. I like these better than the PVC version.



My most used chuck. Its two layers of 1/2” baltic birch glued together and bolted to a 8” faceplate. Again covered with vinyl shelf paper for a seal. The blue donut is a piece of yoga mat. It makes for a seal when I turn green bowls with warped rims.

 

[Emiliano Achaval]

@AlanZ Curly Koa and spalted Hawaiian PVC. 7 inches wide. I'm all set for awhile...

 

[Emiliano Achaval]

I'm not very good when it comes to pictures & computers and sizing and all that stuff. I don't have one of those smart-phones to make things easy. I think (???) I know how to email you some photos....but first I'll have to take the photos, remove the memory card, install it on my computer and download them to my Photos (iMac) then attach them to an email. Is that the correct procedure? Give me a day or two.

No problem, I made a 7 in chuck today...Thank you!

 

[Emiliano Achaval]

Emiliano-
I just recently got my vacuum system working. For the 3" and 4" PVC couplings, I got the Rubber Chucky gaskets. They seem to work and fit quite well.
And I'm jealous that you've got enough koa to use like that.

I have to look into the rubber Chucky gaskets. I know I'm a lucky guy, I have more Koa that I can use in a few lifetimes... Aloha

A couple of my wood chucks. Hard maple with vinyl shelf paper contacted cemented on for the seal. I usually make the big ones segmented. Bought a used but re-sharpened tap off ebay for a few dollars to thread the chucks. After threading I soak the threads in ca and re-thread so they last a long time. On the small one you can see I made a seat for the chuck to run true on the spindle. I like these better than the PVC version.

View attachment 24434

My most used chuck. Its two layers of 1/2” baltic birch glued together and bolted to a 8” faceplate. Again covered with vinyl shelf paper for a seal. The blue donut is a piece of yoga mat. It makes for a seal when I turn green bowls with warped rims.

View attachment 24435

View attachment 24436

I have a set of chasers to make faceplates for my Lathes.. If I make another one I will make one out of Boxwood... Thanks for the help. Aloha

 

[James Seyfried]

I hardly ever remove the cards from my cameras. Instead I use the USB cables that come with the cameras. Cameras also come with software on a CD. If you install it on your computer it will automatically download the pictures when you connect the USB cable. This is quicker and easier than taking the memory card out of the camera and plugging it into the computer. It also is less wear and tear on the memory card and connectors.

Just trying to understand why using the USB cable is better. Is it because the USB cable and it's connectors are less important to the camera than the memory card and it's connectors are? As you could still use the camera if you wear out the USB connector in the camera and cables are cheaper than cards? Or are they more durable? I usually leave my camera on the tripod and take the card to the computer, it seems more convenient. But it won't be if I have to replace the card or camera!