Vacuum chucking notes

[Richard Jones]

I received my JT Turning Tools vacuum system this week, and have been trying to correct an issue with sealing the new handwheel to the spindle of my Jet 1642. I have isolated the leakage to this point. After speaking (AAW forum) with John Giem, who wrote an article in the Feb. 2011 American Woodworker, I will try some silicone caulk at this spot. Aside from machining an internal o-ring, which I would not recommend, I can't see how any manufacturer can have a one-size-fits-all handwheel, especially the way the spindle is machined near the outboard end, so this is certainly not a dig at JT. They make great products. I guess it's possible to remove the spindle and have the outboard end of it machined for a couple of o-rings, but not sure too many folks would go to the trouble/expense. John Giem indicates that caulking is a viable assault in the battle for air ingress reduction (AIR!). I want every ounce of suckage that's coming to me, even if I don't need it.

Anyway, I thought I would comment on some things from a first-time vacuum chucking system user, who has never seen any systems other than on the internet and in magazines.

1. The AW article by Mr. Giem is a gem. Great tips on everything and I can't recommend it enough. Simple enough so that I could understand it, complex enough for the vacheads in the bunch..... And it's written in such a way that, if desired, one can skip over the how-it-works part and get right to the troubleshooting portion.
2. I made my own chucks, 1 1/2", 2" & 3" so far, out of scrap cherry (I have wads of cherry). Maybe plywood or MDF would be better? Not as elegant, but this is a situation where performance counts. When testing/isolating my system, I determined that I was losing almost 2 lbs. of suckage because the cherry was leaking. After a couple of coats of shellac and then lacquer, that situation was resolved. You wouldn't think that a big chunk of solid wood would leak air, but it does, and a lot. BTW, shrink wrap can help you find trouble spots, at least some of the big ones. I first thought that the leakage was at the chuck/spindle connection at the headstock end, but the shrink wrap told the true tale. Wrap some around your chuck and watch your gauge.
3. Time spent troubleshooting/isolating will pay big dividends (see #2).
4. I replaced the small zip ties at the hose/barb connections with hose clamps and picked up about 1/2 lb. of suckage. Nothing major, but every little bit helps when trying to maximize your suckage.
5. Misc. things I forgot about........
6. Misc. things I haven't thought of yet........

I am very interested in what others have to say about fixing/isolating/modding their systems, and wonder if a "sticky" on vacuum tidbits would be helpful.

Thanking you in advance, I remain y'r ob't sv't,

Rich

[Faust M. Ruggiero]

Richard,
Maybe your JT adapter works differently than mine. Doesn't it have two o rings on the portion that fits into your hollow spindle. If so, where is the leak?
faust

[Steve Schlumpf]

Richard, just my experience but plywood or MDF do not work well as a base material. I used hardwood, Cherry, and I made sure that it is sealed well before use. Photo of my chuck can be found in my Vacuum System tutorial here on SMC.

Something to think about is the size of your vac chuck and how it relates to holding pressure. I have a 4" and a 5" chuck and they work quite well for the size bowls and hollow forms that I have turned up to this point. I will probably turn a larger chuck at some point if I ever decide to turn a platter.

Also, seeing as how you are new to this, you already found out how the vac system will pull air through the piece being turned. It will also suck the finish through the piece and into your chuck and spindle if you finish your work on the lathe! Just something to be aware of!

Everyone probably has their own hg setting that they feel comfortable with. I never use more than 20 hg as that provides a heck of a lot of holding power at the size chucks that I use. If you turn thin... be sure to go easy on the vacuum or you will cause the piece to flex or worse!

Have fun with your new system! Tom does some great work, helped me plan/build my vacuum system and I still swear by his vacuum adapters!

[James Combs]

Richard, I have had my homemade system since March of this year and I typically get 26+"hg vacuum and all I have as a spindle adapter is one sealed bearing and a brass fitting pressed into the bearing's center. I did modify the 1642's hand wheel to give me a press fit for the bearing but my point is, are you sure the leak is at the adapter. My experience is that it doesn't take much to seal it there. Take a look at mine to see what I am describing.

If you are still experiencing leakage problems perhaps if you posted photos of your setup and some close-ups of potential leak areas we might be able to provide more advice on where to look and what to check.

[Richard Jones]

Richard,
Maybe your JT adapter works differently than mine. Doesn't it have two o rings on the portion that fits into your hollow spindle. If so, where is the leak?
faust

Faust,

The adapter is fine, it's the handwheel that is the culprit.................

Rich

[Richard Jones]

Richard, I have had my homemade system since March of this year and I typically get 26+"hg vacuum and all I have as a spindle adapter is one sealed bearing and a brass fitting pressed into the bearing's center. I did modify the 1642's hand wheel to give me a press fit for the bearing but my point is, are you sure the leak is at the adapter. My experience is that it doesn't take much to seal it there. Take a look at mine to see what I am describing.

If you are still experiencing leakage problems perhaps if you posted photos of your setup and some close-ups of potential leak areas we might be able to provide more advice on where to look and what to check.

Again, not the adapter, but the handwheel.

Will do some pics tomorrow, for sure. Am pulling 21+, but if you remove the handwheel from the lathe and isolate it, it will do about 23 1/2. Again, I'm sure 21 is fine, probably more than fine, but we all want more power, eh?

Thanks.

R

[Richard Jones]

Richard, just my experience but plywood or MDF do not work well as a base material. I used hardwood, Cherry, and I made sure that it is sealed well before use. Photo of my chuck can be found in my Vacuum System tutorial here on SMC.

Something to think about is the size of your vac chuck and how it relates to holding pressure. I have a 4" and a 5" chuck and they work quite well for the size bowls and hollow forms that I have turned up to this point. I will probably turn a larger chuck at some point if I ever decide to turn a platter.

Also, seeing as how you are new to this, you already found out how the vac system will pull air through the piece being turned. It will also suck the finish through the piece and into your chuck and spindle if you finish your work on the lathe! Just something to be aware of!

Everyone probably has their own hg setting that they feel comfortable with. I never use more than 20 hg as that provides a heck of a lot of holding power at the size chucks that I use. If you turn thin... be sure to go easy on the vacuum or you will cause the piece to flex or worse!

Have fun with your new system! Tom does some great work, helped me plan/build my vacuum system and I still swear by his vacuum adapters!

Steve,

I did use cherry, as I have an abundance of it. Sealed it well, and the system is pulling the same with the chuck as without, so I don't think the chuck is the problem.

I will continue to work on the problem this weekend, hopefully betwixt the SMC Collective this issue can get resolved, and it should benefit others as well.

As stated previously, I'll do some pics and see what all'ya'll think about it.

Thanks again.

Rich

[Peter Elliott]

I just my JT adapter for my Jet 1642. I haven't had time to run it with the vacuum but I did fit it onto the drive shaft and remarked to myself what a good fit it was. The two o-rings on the adapter insert seemed very tight fitting when married to the "hand wheel".

But if you say the JT handwheel part is loosing suction, I can't seem think how possible it is on how close the I.D. is to the drive shaft. If yours has a loose fit, I would call JT and put calipers to both shaft and the hand wheel, then give them the difference.

Look forward to running mine next week!
-Peter

[Ryan Baker]

I also have a JT adapter on a Jet 1642. I don't have any significant leakage at the handwheel. I have the stock handwheel. Back when I got mine, he had you send him the measurement of your handwheel ID and he would machine the adapter to fit. I seem to recall just after that he started making them a standard size and had replacement handwheels with matching ID. Is that what you are using? Is the leaking where the handwheel fits the lathe? Caulk on the machine side may solve the problem. Caulk at the vacuum adapter side is a problem, because you can't remove the adapter.

Vacuum systems are just like that. You spend a while chasing after decreasing leaks until you get it good enough to get the job done. Fortunately, thay are usually pretty easy fixes.

[Richard Jones]

I also have a JT adapter on a Jet 1642. I don't have any significant leakage at the handwheel. I have the stock handwheel. Back when I got mine, he had you send him the measurement of your handwheel ID and he would machine the adapter to fit. I seem to recall just after that he started making them a standard size and had replacement handwheels with matching ID. Is that what you are using? Is the leaking where the handwheel fits the lathe? Caulk on the machine side may solve the problem. Caulk at the vacuum adapter side is a problem, because you can't remove the adapter.

Vacuum systems are just like that. You spend a while chasing after decreasing leaks until you get it good enough to get the job done. Fortunately, thay are usually pretty easy fixes.

Ryan,

Leaking where the handwheel fits the lathe, correct, and it is the newer version. First pic is with the locking collar removed from the lathe, placed over the end of the handwheel, like it would be if it were assembled. 2011-10-21_11-45-58_368.jpg
Second pic is where the handwheel and locking collar have been caulked with silicone and reinstalled.2011-10-21_12-16-23_461.jpg

Better, but still leaking some, can't see how it can't leak, between the split collar and threads. I'll keep working on it until it is as good as this: 2011-10-21_11-16-19_320.jpg This is about 23 1/2, vs 22 1/2 at the chuck. I even wrapped the handwheel/locking collar with shrink wrap, but it didn't help any. Narrowing it down, sort of fun trying to figure all this out.

Thanks for all the help.

Rich