Take That, Tenon Chuckers!

that sounds like a justification for a vacuum chuck system, george... remember, you can't take it with you and there's no use leaving anything for the kids to fight over.. *g*

mac

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The NOVA has a built-in capability, but somehow I think a vacuum chuck on a

Hi George

Tailstock brought up with a soft pussy foot to keep the bowl in place and ugly or no recess would make for NO problem, resurfacing inside and also outside heel marks, and a vacuum chuck if used with a proper sized vacuum drum chuck also would fit the bill.

Have fun and take care Leo Van Der Loo

George wrote:

if you had a vacuum system, you wouldn't be drilling holes in the bottoms, right?? (I am probably wrong.. when I saw the cost of vac, I quit learning about it)

mac

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No, the vacuum chuck is used for light work only. As Leo mentioned, if I made a huge cup to set the rear of the bowl in, then played to get it centered, then had enough of a pump to maintain a suitable vacuum through that much thin end grain....

Well, you get the point.

Fortunately, I don't have to take such extraordinary measures. What Leo thinks is ugly without ever having seen it held the bowl perfectly, and was not damaged at all in the process. Not to mention, it was prepared and sanded before the bowl was reversed to hollow, so no third mount was ever necessary!

If you do a bit of researching on the net you will see that you can make a vac chucking system with very little cost. Use an old freezer compressor for the vacuum and make a rotating joint with some sealed bearings - the ease of the rotating joint manufacture depends on what kind of outboard spindle arrangement you have. I used an old 2 piston rather large refrigeration compressor but bought a Oneway rotating joint. I made my own drum chucks out of ABS pipe connectors. Billh

hmm... maybe it's just tool envy, but vacuum chucking sounds like a PITA..

mac

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Hi George

I will insert a few words so as to not give the impression that I "find your recess ugly without seeing it"

Beautiful- Pretty - Ugly or NO Recess it would make NO PROBLEM, to do both inside and outside of a bowl turning where you had sanded but not noticed the heel pressure mark or other imperfections that make us go back and try to improve upon, be that just some scratch marks or crushed grain. The point of all this is that "there are more ways to skin a cat" as they say, or yes there are many good ways to hold, turn or otherwise change the shape of a chunk of wood, besides the way you have shown us, and the ways others have used and are using, just be careful you don't get hurt doing it.

George wrote:/snip/

What Leo

Hi Mack

You might be living on a low budget, but a vacuum system is easily build by anyone with very few tools or dollars,

You might have seen the one that I made, it's on my site, I happened to have a small compressor, but you can use other setups, car ac units, big old freezer compressors or old truck refrigeration unit compressors, etc. A couple of sealed bearings and turned plug to go into you headstock shaft and a hose barb or two, bleeder valve and some plastic hose and open cell foam for filtering, and some time to stick it all together, there are some plans on the net if you do need help visualizing it.

mac davis wrote:

SNIP .......

==================== Mac, Check out the older automotive wrecking yards in your area. One of the old York style (60's-70's) auto air conditioner V-twin compressors will make a good vacuum system. (Later ones will probably do OK, but I haven't seen one of those) Make a bracket to mount it on a piece of plywood, along with a 1/4 HP 1750 RPM electric motor to turn it just above idle speed for the car it came from. Some vacuum line and parts from your local auto parts place and a some skate board bearings to make your rotary connector, and you're ready for vacuum chucking. Doesn't have to be expensive at all.

Ken Moon Webberville, TX.

For those contemplating salvage systems, remember that Freon was its own lubricant, so you'll have to provide some or seize the system. Hopefully not while you've got something hanging up there that could smack you.

Well Leo.. it's tempting, BUT... *g*

Just got the new lathe, (2nd one since November), several new chisels and scrapers, new chain saw.... and my coring system should get here tomorrow... (on our anniversary, just for weirdness) I think my budget and learning curve are both going to be too busy catching up for any new stuff for a bit.. *g*

mac

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good point.. and (at least in Calif.) you can't buy freon any more...

I was actually thinking that if I used my Harbor Freight compressor for the vacuum system, I could shop for a new (and quieter) compressor... *g*

mac

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For vacuum, high air-flow is better than high pressure. A household vauum cleaner is sufficient, provided it has a by-pass valve to stop the vac motor from burning out from lack of airflow.

Depending on the lathe, a rotation joint is not necessary. A tin can can do the job! Mine is sized to fit over the handweel and secured to the headstock with a disk of 1/2" ply, cut in half and drilled to fit closely around the spindle. Oiling the spindle then applying a bead of silastic around where the ply joins the spindle seals it enough for the vacuum to work. (It's highflow, not high-pressure, remember.) A hole cut in the other tin-can for the hose from the vac and voila!

It generates sufficient pressure to do light touch ups to the foot of a bowl, careful removal of the tenon, reshaping, etc.

Even a commercial vac-chuck set up won't allow more than a light touchup and a tin can's a darn sight cheaper...

- Andy

Hi Mac

I'm glad to hear you won't be sitting idle, after your anniversary.

HAPPY ANNIVERSARY MAC

Have fun and take care, for many more of the above. Leo Van Der Loo

mac davis wrote:

I think the force holding the bowl onto the drum chuck or faceplate is approximated by 0.5Xvacuum in inches of mercuryXarea of workpiece under vacuum. For large diameter pieces this can be a very large number and can implode/crack the workpiece if it is thin. If the diameter of the bowl is around 6" or larger under a good vacuum you can do a lot more than just light touchup cuts. billh

============================ George, The older York compresors had an oil sump. The oil has a look similar to hydraulic fluid. I saw a demo of one that had been in use for several years with no lubricant problems.

Ken Moon Webberville, TX.

With my setup the smallest dia I can safely hold is around 8-9", but your formula suggests I should be able to safely hold larger pieces before needing to worry about cracking. I haven't tried it with anything over 18" dia so I can't speak from experience.

The only commercial systems I've tried are the Vicmarc & Nova units (newly set up on friends' lathes) with about 12" bowls and I could still only do light touch-ups but that could easily be due to incorrect setup. You know, the "Oooer! A new toy... let's whack it on the lathe and see what we can do. We'll RTFM later." type attitude.

Regardless of the system used, including a pressure gauge & adjustable by-pass valve would, I think, increase the versatility but this is something else I haven't tried. Yet.

- Andy

Certainly, but it _is_ the exception, isn't it?