Rotary vacuum adapter for vacuum chuck setup

[Alan Heffernan]

I am putting together a vacuum chuck system for my PM3520A and have a Gast vacuum pump on order. I am now trying to decide which rotary vacuum adapter I should get.

Is the rotary vacuum adapter sold by Craft Supplies that they call "Precision Machine Rotary Vacuum Chuck Adapter" the same as sold by JT Turning Tools? Here are a couple of photos of the Craft Supplies offering.
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[Bob Bouis]

I don't think they're the same. But keep in mind it's just a round thing with a hole drilled through it, some o-rings one end and a couple $1 bearings glued into the other -- and you have a $4000 machine that makes round things.

[John K Jordan]

They do look very similar and as mentioned, are extremely simple in design so I expect the function to be the same. The one from Craft Supplies is a lot cheaper!

I bought the bearings and parts to build one from scratch but have not done it yet. I plan to machine one from aluminum similar to what you pictured but construction can be simpler than that. I can imagine turning a piece from lignum vitae that would hold the o-rings and adapt to the bearing. Also, Joe Woodworker has instructions and parts for a design that could easily be adapted to fit the PM lathe: http://www.joewoodworker.com/veneering/vacuumchucking.htm

If you haven't see Joe's web site he has a lot of good info on building vacuum chucks, etc as well as a more complex vacuum system suitable for vacuum bagging and clamping as well as vacuum chucking on the lathe. He sells everything you might need at extremely good prices, including an excellent vacuum chuck gasket material.

I currently have the Oneway adapter and it is a pain to use since the handwheel must be removed and the adapter fastened in place. Some people leave it in place but I do a lot of spindle turning and need access through the headstock spindle. I like the design with the o-rings.

JKJ

[Pat Scott]

I have the JT Turning adapter on my 3520b. It sure is nice to be able to push it in and remove it as quickly, so I highly recommend it. I've owned it for years with no problems. It has two o-rings, I see the Craft Supply version has 3. If price is the same between them, I might go for the Craft Supply version simply because of the extra O ring.

[Steve Schlumpf]

I have one of JT's original vacuum adapters and it was made specifically for my lathe! I highly recommend Tom's vacuum adapter!!

One of the issues Tom ran into when figuring out the design was discovering the internal diameters of the handwheels on lathes were not consistent. When dealing with a vacuum, you have to have a tight fit or you will not create a vacuum. Tom's solution was to create a matched handwheel and vacuum adapter for each model of lathe. Things may have changed since I got my adapter, so I highly recommend going to the JT website (http://www.jtturningtools.com/vacuum-adapters) and reading about the adapter he developed. Please note that on the info page for the Powermatic 3520 A & B, it states that the adapter will not work with the stock lathe - which leads me to believe that he is still machining a matched set.

[Michael Schneider]

I like using the vicmarc system. Your Chuck holds the adapter, so it is very fast to switch between traditional chuck turning and vacuum chucking.

I already use vicmarc chucks, so I did not have to buy the adapter.

http://www.woodworkersemporium.com/Vicmarc_V01216/

[David C. Roseman]

Alan, from the Craft Supplies artwork and description, I don't think they're the same thing. I suggest you just call Tom Steyer at JT Turning Tools and ask him. Craft Supplies describes theirs as a "double row, dual thrust" bearing. Their unit may be good, but I'm not sure what that means. Sounds like a marketing description. I know that Steyer uses two double-sealed, double-shielded bearings, and the housing is machined with CNC equipment from a single billet of aircraft aluminum. His don't leak. :) But if you're pulling a vacuum that is strong enough, with high enough CFM, some leakage is o.k.

[Doug Ladendorf]

That looks pretty interesting Michael and I also have Vicmarc chucks. I can't seem to find much info online about these though. Would love to see a video of how they work.
Doug


I like using the vicmarc system. Your Chuck holds the adapter, so it is very fast to switch between traditional chuck turning and vacuum chucking.

I already use vicmarc chucks, so I did not have to buy the adapter.

http://www.woodworkersemporium.com/Vicmarc_V01216/

[Jeramie Johnson]

I just spoke to Tom this afternoon about a wheel/adapter/hub for my G0766, which I already have a Ghast setup. I was waiting for him to get settled after being at a SWAT the past weekend. I can post an update and pictures when I receive mine.

[Josh Bowman]

Alan, just to muddy the water, I have made a few from HDPE round stock, a sealed wheel bearing and a brass fitting. Buy a fitting to fit your air hose from somewhere like Lowes and take that to an auto parts store and have them pick a bearing with a close fit for one end of the fitting. Either epoxy it into the inner race or put a nut on each side of the bearings inner race to hold the fitting in place. Now simple turn the HDPE round stock to shape, similar to the one you posted above and drill a nice tight fit for the outside of the bearing in the HDPE and press the bearing in. Use a parting tool to cut a couple of grooves in the nose that goes into the lathes hand wheel. It's fun to make and cheap, I'm thinking something like 10 to 15 bucks for parts and it works great.

[Larry Copas]

I don't know if it is more fun making stuff on the wood lathe or making new toys for the wood lathe.

Here is my adapter. Two 6203 double sealed bearings sealed up with a shaft seal. I thought of using three o-rings but I was thinking I could leave a boss on my shaft for a hose washer to seal against.

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It appears to be a good solution but I'm still building my new vacuum system and haven't tried it out yet.

[Tony Rozendaal]

As long as we are muddying the water:-) , here is one I made recently to fit more than one lathe. It uses a lamp rod to go all the way through the headstock to a morse taper adapter that is small enough to thread a cup chuck over it. The MT adapter and the bearing end are made from black walnut. The coupler is made from a barbed fitting machined down to fit through two 3/8 ID x 7/8 OD bearings. It can move from lathe to lathe by putting a longer or shorter lamp rod in it. Or, by running the larger piece near the coupler end up against the outboard end of the spindle.

[Alan Heffernan]

I don't know if it is more fun making stuff on the wood lathe or making new toys for the wood lathe.

Here is my adapter. Two 6303 double sealed bearings sealed up with a shaft seal. I thought of using three o-rings but I was thinking I could leave a boss on my shaft for a hose washer to seal against.

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It appears to be a good solution but I'm still building my new vacuum system and haven't tried it out yet.
Larry, very nice design. Tell us more about the shaft seal please!

[David C. Roseman]

I just spoke to Tom this afternoon about a wheel/adapter/hub for my G0766, which I already have a Ghast setup. I was waiting for him to get settled after being at a SWAT the past weekend. I can post an update and pictures when I receive mine.

Jeramie, Tom has a good setup for the G0766. I think the first G0766 he made one for was mine last year. Here's the review I did then, with pics. http://www.sawmillcreek.org/showthread.php?238452-Review-of-JT-Turning-Tools-Vacuum-Chucking-accessories-for-Grizzly-G0766-(and-others)

[David C. Roseman]

I don't know if it is more fun making stuff on the wood lathe or making new toys for the wood lathe.

Here is my adapter. Two 6303 double sealed bearings sealed up with a shaft seal. I thought of using three o-rings but I was thinking I could leave a boss on my shaft for a hose washer to seal against.

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It appears to be a good solution but I'm still building my new vacuum system and haven't tried it out yet.


Very interesting design, Larry. Could you elaborate a bit? I'm guessing from the pics that your bearing assembly fits inside that housing, which then threads onto the outboard end of the spindle in place of the OEM handwheel? It looks like you've threaded the outboard end of the housing/handwheel for a fitting to connect the hose. If that's right, doesn't that defeat the purpose of the bearings, since the housing will rotate with the spindle? A more minor point, won't you have to take both the housing and the bearing assembly off in order to use your knockout bar? Or maybe use a very thin knockout bar?

[Bill Boehme]

Larry, very nice design. Tell us more about the shaft seal please!

Shaft seals are a necessity to stop leakage and to prevent the grease from being sucked out of the bearing. They are disk shaped rubber seals with a spring that provides a tight seal around the shaft. They go on the high pressure side of the bearing. Also a rotary coupler needs at least two bearings to prevent deflection between inner and outer races. The JT rotary coupler meets these requirements. From their description, I would guess that the Craft Supplies unit doesn't ... their description says bearing which sounds like one bearing to me.

[Larry Copas]

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Running at 1,000 rpm on my General 260-20.

Rotary shaft seals are commonly available that will hold 10 psi at the speeds we would be turning with a vacuum chuck installed. Heavy duty seals are available that will hold 50 psi. The problem is finding the right size at reasonable cost.

Anybody might note the hose ring is a 1/2" pex fitting which works great on 3/8" braided vinyl hose. Lots better than a hose clamp and I think it looks professional.

[David C. Roseman]

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Running at 1,000 rpm on my General 260-20.

Rotary shaft seals are commonly available that will hold 10 psi at the speeds we would be turning with a vacuum chuck installed. Heavy duty seals are available that will hold 50 psi. The problem is finding the right size at reasonable cost.

Anybody might note the hose ring is a 1/2" pex fitting which works great on 3/8" braided vinyl hose. Lots better than a hose clamp and I think it looks professional.


Larry, thanks for the followup pic; pls disregard my earlier questions. I see now how your setup is assembled and mounted, using the OEM handwheel. Very nice job.

[Alan Heffernan]

Larry,
I am familiar with oil and grease seals used on shafts. Does the one you use require lubrication to avoid premature wear? Is it a "lip seal"?

[Bob Bouis]

Also a rotary coupler needs at least two bearings to prevent deflection between inner and outer races.

From the weight of the vacuum hose? Usually people say they use two bearings because it reduces air leakage through the bearings.

[Larry Copas]

Larry,
I am familiar with oil and grease seals used on shafts. Does the one you use require lubrication to avoid premature wear? Is it a "lip seal"?

It is called a lip seal I think. According to Parker a seal without lubrication will fail in a few hours. I packed the recess of the seal with grease. No idea if it will work but plan to pull it apart after running it for a substantial time to check for wear. Since both of my bearings are also sealed the extra seal may not have any or little effect on operation of the adapter.

[Alan Heffernan]

I am putting together a vacuum chuck system for my PM3520A and have a Gast vacuum pump on order. I am now trying to decide which rotary vacuum adapter I should get.

Is the rotary vacuum adapter sold by Craft Supplies that they call "Precision Machine Rotary Vacuum Chuck Adapter" the same as sold by JT Turning Tools? Here are a couple of photos of the Craft Supplies offering.
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After the great responses and shared experience here, it is obvious the adapters sold by JT Turning Tools and Craft Supplies are not the same. Your responses have helped me dig deeper into this hardware and the differences in offerings and options out there.

From the suppliers descriptions:
1. JT turning Tools uses two separate sealed ball bearings and it is "assembled with a special, proprietary sealing system installed between the bearings".
2. The Craft Supplies unit uses one double row, dual thrust sealed bearing. (This is effectively two sets of bearings in one housing).

In terms of seals, beit bearing or shaft seals, they need lubrication. The seals on the bearings in question get it from the lubrication that they come with from the factory. Seals are used to keep the lube in and debris out. As we know, seal failure is what typically kills a bearing. The seals go, the lube is lost and/or they get debris inside.

I spoke to a knowledgeable engineer and he reminded me that the seals on a bearing have some capability to resist pressure and encouraged me to dig into the specs on the specific bearing used. He owns several high vacuum systems for his R&D and prototype development work. Of course his systems are very expensive, often have multiple pumps and require far more attention than what's needed to provide my hope to spin a piece of wood. But it is interesting to talk to him and ponder this topic.

Of course I do not have the specifics as to the actual bearings being used in the Craft Supply unit, other than it's a double row, dual thrust bearing.

So that leads me to my current assumptions. I assume that the seals on the double throw, dual thrust bearing that the Craft Supply unit uses can handle a fraction of one atmosphere of external pressure. From the photos on the Craft Supplies site, the effective surface area of the outboard seal does appear to be relatively quite small and therefore would suffer less deflection due to the external pressure created by the partial vacuum. I have no idea what the inboard seal looks like.

Bottomline, the relative simplicity and low cost of the Craft Supply unit make it attractive to me for a trial. When I lay hands on one and time allowing, it will be fun to dig deeper into the specs on the actual bearing used.

[Jeramie Johnson]

Jeramie, Tom has a good setup for the G0766. I think the first G0766 he made one for was mine last year. Here's the review I did then, with pics. http://www.sawmillcreek.org/showthread.php?238452-Review-of-JT-Turning-Tools-Vacuum-Chucking-accessories-for-Grizzly-G0766-(and-others)

Thank you for redirecting me to your review. Very much appreciated.