After doing quite a bit of research on the topic, I pulled the trigger on a Harrison Vac chuck and Robinaire pump.  I've got it installed and working...that is pulling a vacuum strong enough to stick a bowl on there. 

 

I can't seem to shake the feeling that I'm getting ahead of myself.  What is in the secret sauce?  I would appreciate the benefit of your experience.  In other words, what in the heck do I do now?

 

The gauge is pegged out showing in excess of 30" of vacuum.  Is that normal?

 

 

 

 

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Thats why the gage only goes up to 30 for a perfect vacuum is supposedly 32 and those fire trucks I use to drive  when we at a farmers irrigation well trying to draft a tank of water to fight fire,25 lbs was about all we could ever see on our gages..and every extra foot of height the water was down from the pump meant it was that much more harder for that pump had to work to get that water in those pumper tanks. If the water was 32 foot straight down no pump could ever suck any water...  Now what do you do next?? close your eyes and run.

Hopefully @Gerald will jump in. He uses a vacuum chuck  but I’m not sure of the manufacturer.  

I wonder if the gauge is accurate. A perfect vacuum is -29.92 in of Hg G

I’ve heard good things abouthttps://www.frugalvacuumchuck.com/

One of my sons-in-law got a PhD in plasma thrusters (rocket science).  One time he showed me the chamber in the lab.  It was about the size of a compact car.   He said vacuum pumps pumped out as much air as they could.  The remaining contents got passed over liquid nitrogen that froze the remaining air molecules to get as perfect a vacuum as possible.   There was a small porthole and the thruster was a tiny plume about the  size of a pilot light.  He now runs a company manufacturing them.  I don't know a lot about it, but I think they are used in satellites to hold their position.

I have seen them demonstrated a few times but never played with one. I’m basically a paranoid when it comes to holding things on the lathe. Do they ever break the seal and lose vacuum ? Except for that minor item they seem like a great idea. 
Paul

57 minutes ago, kmealy said:

vacuum pumps pumped out as much air as they could.

I’d almost forgot about using a vacuum pump in electronics. That’s how they made “vacuum tubes”. Instead of nitrogen they would ignite a getter that would burn an oxygen absorbing material. 

9 hours ago, Masonsailor said:

I have seen them demonstrated a few times but never played with one. I’m basically a paranoid when it comes to holding things on the lathe. Do they ever break the seal and lose vacuum ? Except for that minor item they seem like a great idea. 
Paul

 

I am not a turner, but I would be in this camp... frisbees come to mind

I have never invested in the vacuum chuck idea.  I have always been a doubter on the hold.  The system also relies on a gasket and I have wondered about the crush rate of the gasket.  I think the bowl would never sit perfectly and a wobble would be there.  I use the flat jaws available for most chucks and have had good luck with them.  I usually add fiber tape or narrow stretch wrap as an insurance.  I also have an 8" backing plate that I mount MDF to and carve a recess to fit the bowl rim aiming for a press fit.  I then use stretch wrap or some fiber tape to secure the hold while doing the bottom.  What ever the choice for doing bowl bottoms light cuts and caution are key. 

What day is the test?  How many questions?  Will it count toward our over all year grade?  Asking for a friend.  

I used the V chuck this morning.  While 2nd turning a bowl, I got a bad catch and broke into the mortise.  Fortunately, there was enough material to create a tenon.  I turned the bowl around and used the tailstock for support and help find the center.  Opening the valve on the christmas tree allowed me to control the amount of vacuum to easily correct any wobble. 

 

Gentle cuts, with pressure toward the headstock and bada bing bada boom...a tenon.  Worked like a champ.  Setup was a little quicker than the cole or longworth chuck.  The bowl still had a pretty rough finish at this time.  I expect that a sanded and finished bowl would have even better adhesion.  

 

I think the biggest advantage will be a non-marring way to mount and finish the bottom.  That said, I don't think it will ever stand up to any aggressive cutting.

 

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I have the Frugal Vacuum system. It came with < or I selected< a pump with tubing , gauge, valve , and one chuck with lamp rod to connect to pump.I love  some more than others a it but it has limitations which you have to work within.

 

All woods are porous but some more than others and you may have to compensate. Wood that has cracks or holes require fill or tape. You will not get more than 28 on a vacuum chuck and that only on a sealed surface. Unfinished wood just will not get that high , maybe 24. There are so many variables to reduce vacuum such as the hose connections, hardware tees. At even 23 the vacuum is very strong to a straight pull force but a catch will probably pop the bowl right of. This is why tailstock support is advised. Also light cuts. Vacuum chuck is not for shaping , only bottom cleanup and tenon removal. I have removed the last vestige with as little as 10. I do not use vacuum on bowl till finished sanding and you can apply finish to inside to help reduce leaks.

 

A real advantage of the Vacuum chuck is that you can easily adjust the bowl if it is set up off center. But just lining up that dimple in the ten0n is no guarantee of alignment. 

 

Rubber Chucky has gaskets but the one I tried did not fit my chuck well . So I use the self adhesive foam sheets from WM crafts section.

 

Frugal Chucks has info on site about making you own chucks and I have made three. Using PVC heavy (don't know the schedule) you can adapt a large chuck down to 2 inch but the longer the extension you add the more unstable the pipe is unless you glue it on. Also adding sections creates more leak chances.

 

One more thing is I usually get no higher than 750rpm when using the vacuum, maybe this is just me. Just feels safer for me and the bowl I spent all that time making.

Photos showing finishing sequence. 

 

Prepare to reverse mount chuck with 1 1/4 x 8 MT adapter in tailstock

 

Screw chuck onto adapter.

 

 

Fire up the V Chuck and move tailstock forward to engage. 

 

 

Release jaws to free bowl.  No wobble.

 

Finished bottom of bowl using V chuck.

 

 

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