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PVC drive chuck

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I am working on hollow forms and saw something that looked useful for trimming the foot. It was a PVC disk with turned grooves that accepted PVC pipe sections The concept was to have one base that held 4-5 different diameters of drive chucks. This was not a vacuum chuck, just something to hold the exterior of the piece along with a live center in the tailstock.
Does this sound like something you have seen? I believe it was made in Canada.
Unfortunately I cannot find the website.
Bob
 
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No, but easily made. A wood disc would with grooves would be easy to make and cheaper vs pvc. A tenon or mortice on the back for chuck jaws.

I have a wooden inverse cone I use, but the idea of using a pvc fitting or pipe section is a good one.
 
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JT Turning Tools used to make one from aluminum for vacuum chucking. It works great, but, unfortunately, Tom passed away a while back and no one is making them to my knowledge. I tried to get Brent at Robust interested in offering them since he makes a knock off of Tom's vacuum adapter, but no joy yet. These used a single 2" groove that could hold pvc adapters from 2" to 6" in diameter. Allowed a relatively easy change in diameter of the vacuum chuck. They work beautifully - a simple, elegant solution that will outlast me.
 
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Another option, and one that holds the piece more securely, is an arbor and reverse cone from rubber chukky. I have/use the std and mini versions that go down to ~3/4" hole. The mini goes down to ~1/2" hole. More expensive vs using pvc pipe or fittings, but the piece can't go flying off when the tenon is cut through.

 
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I had not seen the Rubber Chucky, it looks good.
What about a burl hollow form with a natural edge opening? Wouldn't an external grip be less likely to crack ? I am leaning towards the vacuum drum seal on PVC pipe.
I will also start to price out a vacuum system.
 

Dave Landers

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I do the bottom of most of my hollow forms with my vacuum chucks - often without vacuum, just held between the chuck ring and live center. Works well for most forms.
I have home-made versions of the reverse chucky, and they work in some cases for me - but the vacuum chuck ring works with almost everything.
Vacuum chucking is (IMO) sketchy on a tall vase-like form - too much leverage at the tailstock end to trust for finishing the entire bottom. But I will usually turn on the vacuum and, if it seems ok, gently take off a tiny nub that I couldn't get with the tailstock there, and sanding sometimes. I often reinforce the vacuum with stretch wrap and blue tape - at least if it comes loose it won't go flying.
 
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I had not seen the Rubber Chucky, it looks good.
What about a burl hollow form with a natural edge opening? Wouldn't an external grip be less likely to crack ? I am leaning towards the vacuum drum seal on PVC pipe.
I will also start to price out a vacuum system.
I have used it with natural edge forms. Sometimes use some painters tape to help hold the upper cone end. The shaft running to the bottom of the form, with a rubber stopper on the end, provides most of the reactionary force to hold the piece in place. The cone at the top applies little pressure (adj, apply as much as desired). The piece is less likely to crack vs an external grip which has to apply more force, but both approaches work well. The chukky has the advantage of applying force directly through the piece bottom and into the live center point, and when the e nub is cut through, the piece doesn't have much room to move, unlike using external grip.
 
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JT Turning Tools used to make one from aluminum for vacuum chucking. It works great, but, unfortunately, Tom passed away a while back and no one is making them to my knowledge. I tried to get Brent at Robust interested in offering them since he makes a knock off of Tom's vacuum adapter, but no joy yet. These used a single 2" groove that could hold pvc adapters from 2" to 6" in diameter. Allowed a relatively easy change in diameter of the vacuum chuck. They work beautifully - a simple, elegant solution that will outlast me.
Resurrecting an old thread. I'm fuzzy on how this worked. can you elaborate? Know of any photos anywhere? Maybe I can make one.
 
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Resurrecting an old thread. I'm fuzzy on how this worked. can you elaborate? Know of any photos anywhere? Maybe I can make one.
Here’s a couple of pics of the JT Turning Tools vacuum hub with pvc adapters and the Rubber Chucky seals. I either use it with the rubber Chucky seals or without depending on whether the seals compress too much. If so, I pull the seal and sub in a loose piece of 1/16” foam as a seal - less movement from compression.
DFDFED22-1204-44EB-904B-73E1FDAAFC3F.jpeg1DB0CC59-02AC-441A-90EA-05E012ABF9B4.jpeg
 
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Thanks Jeff. I think I saw a guy selling those on eBay. He didn’t have squat for photos and I didn’t understand how they worked. I get it now. How do they do for running true/concentric? Do you trim/true the PVC adapters after mounting? And, what keeps the PVC to chuck joint from leaking?
 
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Thanks Jeff. I think I saw a guy selling those on eBay. He didn’t have squat for photos and I didn’t understand how they worked. I get it now. How do they do for running true/concentric? Do you trim/true the PVC adapters after mounting? And, what keeps the PVC to chuck joint from leaking?
The one’s from JTTurning Tools run perfectly true. I true up the rim of the adapter with a scraper when mounted and give it a rounded profile. The recess that the adapter seats in has an o-ring that seats in a groove towards the bottom that acts as a seal. No leaks. The six set screws around the outside really aren’t necessary - I usually leave them loose.
 
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The one’s from JTTurning Tools run perfectly true. I true up the rim of the adapter with a scraper when mounted and give it a rounded profile. The recess that the adapter seats in has an o-ring that seats in a groove towards the bottom that acts as a seal. No leaks. The six set screws around the outside really aren’t necessary - I usually leave them loose.
Jeff, thank you. After your post I searched and found an article on them. One thing that wasn't perfectly clear was regarding that O-ring. Is it on the "side" of the part that sticks into the PVC adapter? Like a piston ring, or is more at the bottom where the PVC adapter pushes down against it? The piston seal would be the better performer, but I don't see how he'd machine a gland (o-ring groove) down in that round hole unless it's made in 2 parts, which it may well be. The guy on eBay is proud of them, but I really like the concept. Especially if they work well.
 
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The o-ring just sits at the bottom of the groove that the pvc adapter slides into. Its sized to the smaller diameter of that groove so it would effectively seal the base of the adapter against the bottom of the groove. I had to go out to the shop and check. Evidently it works fine since I have used mine for about 14 years without ever removing the o-ring until tonight. My vac system always pegs the needle - but then my shop is about 120ft from sea level - we can hear (and see) the water lapping on the beach below us.
 
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Jeff, thanks again for checking that detail. Last question I think... Since the O-ring is at the bottom of the groove, how tightly does the 2" adapter area fit onto the hub's core? Slip right on easily, or do oyu have to work it on, etc. I realize that in use everything should be pulled together from the vacuum. So what I'm after is how easy for the PVC adapter go on or off in use or when you want to swap?

And for what it's worth, a PVC fitting actually tapers. A 2" fitting's socket gets narrower at the bottom by 0.018 over its 1.16 length. So I wonder if its a little loose going on, then gets tighter as it goes down. His groove doesn't look very deep. You said you don't usually need to worrk with the set screws so I'm presuming it gets tight? Concentrically I mean.
 
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