Advice on using a vacuum chuck.

[Bill Wyko]

A few weeks ago I got a Oneway 5" vacuum chuck. I've never used one and I'd like to review it for you guys. If you guys can give me any advice on centering, project size, safe use, various applications or anything else you can think of, I'd appreciate it. I want to review it properly and fairly.

Thanks,

[Steve Schlumpf]

Bill - have you used any type of vacuum system yet? If not, then take some time to understand the principles behind the hg reading and the size of the chuck used. Very little changes in hg can have drastic changes in pounds of holding force. The 5" chuck you mention is a fairly large chuck and will support a quite large blank but always keep safety in mind when using it by keeping the tailstock in place until the last possible moment - then sliding it out of the way and finishing the turning.

Centering a piece can be a hit or miss thing ... or you can pick up one of those chuck adapters for your tailstock and use it to center the piece on the vacuum chuck - while the blank is still being held by the chuck used to turn it. Lots of options.

[Dan Forman]

I find centering to be pretty sure under two conditions. One is to use the morse taper chuck adaptor that Steve mentioned. The chuck screw on to it as if it were the headstock spindle, and it's placed in the tailstock, then moved up the the vac chuck, which leaves it perfectly centered. The other option only works if you remembered to make sure there is an indentation from the live center in the center of your tenon or recess. That has been good enough for me to bring up the tailstock and place the piece on the live center, then slide it up to the vac chuck and the piece will be centered.

Occasionally I have trimmed the tenon enough to lose the original mark, and forgotten to make a new indentation. I have made a little device that consists of a wood cylinder turned to precisely fit the opening in the back of the chuck just ahead of the spindle threads - and that shoulders against the back of the chuck to square it. I drilled this to about 3/8" (could be anything really), and then insert a centering punch the same diameter as the hole. It should fit very snugly. So if I need to remark the center of the tenon or recess, I just remount in the chuck, insert the device in the back of the chuck, and bang the center punch once with a mallet. I now have a center point to use with the live center to mount the piece to the vac chuck. It has worked very well the few times I have needed it.

Trying to mount without a reference point is rather difficult. I have done it well enough once to apply and rub in an oil finish, but I wouldn't have wanted to use a tool on the bowl, as I couldn't get it to run very true, even after many attempts to straighten it with minimal vacuum applied.

When trimming tenons on the vac chuck, I use a scraper and take off the material by pushing in toward the headstock, no more than 1/8" at a time, rather than using a bowl gouge and applying force perpendicular to the ways. That lessens the chance of pulling the bowl off center. Final cuts to shape the "dish" are done gently, usually with a rounded scraper or the edge of a rounded skew chisel used as a scraper, which generally leaves the cleanest surface for me.

Have fun with the chuck, I think you will find it very helpful.

Dan

[Josh Bowman]

Here you Dan and Steve.

[James Hamilton]

Have you tried hooking that house vacuum up to the lathe? That Orek guy says his can hold a bowling ball, no problem... :D

[Bill Wyko]

I do a lot of vacuum work with veneers when I build humidors. I use the same vac for the chuck. I really appreciate all the info. Any place you guys can recommend to get the reverse chuck adapter? Possibly a SMC sponsor? That would have come in handy today actually. I'm finishing up another segmented turning, down to gluing the 2 halves together & removing the tenon tomorrow.

[Steve Schlumpf]

Bill - I use a Oneway Talon chuck and picked up the adapter while at the St. Paul symposium this past June. Have to admit, I have yet to use it as the center point that is left when roughing out the form has always worked great and has been very quick!

[Bill Wyko]

Thanks Steve. Another question I have, has anyone imploded a piece they turned thin and applied vacuum to? I worry that if I apply vacuum to a vessel that's deep and thin, I may implode it.

[Jason Clark2]

I've done it a couple of time intentionally on small pieces because I wanted to know what happens. The lathe wasn't running so no shrapnel but it's very very loud.

Jason

[Alan Trout]

Bill,

Yes you can implode a piece. I did a small thin mesquite bowl to see if I could do it, and I can. That is the reason you have a bleed valve so you can limit the amount of vacuum. I start mine with a lot of vacuum bleeding and adjust the valve to bring the amount of vacuum up to where I feel comfortable.

Alan

[John Giem]

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Trying to mount without a reference point is rather difficult. I have done it well enough once to apply and rub in an oil finish, but I wouldn't have wanted to use a tool on the bowl, as I couldn't get it to run very true, even after many attempts to straighten it with minimal vacuum applied.

Dan

Mounting and centering a turning on a vacuum chuck without a reference mark is not that difficult when using the right process.
1. Mount turning on chuck centering it by eye.
2. Bring tool rest up and place end adjacent to tenon, just as close as possible and still be able to rotate turning by hand.
3. Reduce vacuum to about 5 in Hg. This should still hold the turning on the chuck yet allow it to be adjusted.
4. Looking straight down from above, rotate turning and locate point where the tenon is closed to the end of toolrest, move toolrest very close to tenon but do not touch it.
5. Rotate turning while looking a the gap and find point where the gap is the largest.
6. Using a wooden mallet or block of wood, lightly tap the tenon on the side away from the tool rest. By tapping toward the toolrest, reduce the gap between the toolrest and tenon by half.
7. Repeat steps 4 through 6 until the turning is 'close enough'.
8. Increase the vacuum level to the desired amount and proceed with your project.

I always try to use the centering mark on the tenon to make remounting easier. However, there are cases where a centering mark is not available or you do not want to mar that surface. For example, a completely finished bowl may be needed to be remounted to to correct an error. I have successfully used this technique many times to remount bowls, coasters, trivets, etc. And Yes, bowl warpage makes things a little tougher.

[John Giem]

Bill,

Yes you can implode a piece. I did a small thin mesquite bowl to see if I could do it, and I can. That is the reason you have a bleed valve so you can limit the amount of vacuum. I start mine with a lot of vacuum bleeding and adjust the valve to bring the amount of vacuum up to where I feel comfortable.

Alan
I had a student testing his vacuum system for leaks and needed something to put across the vacuum chuck to seal it off. (I use masonite or sheet aluminum.) He 'borrowed' a saucer from the kitchen and proceeded to do his testing. I understand that his wife was louder than the imploding saucer.

[Dan Forman]

John --- Thanks for that writeup. The bowl I was referring to was completed and the tenon was completely gone. I tried to watch the wobble of the rim and work with that, but without the a fixed reference point, it was pretty hard. I tried using spots on the wall, but it didn't work very well. The tool rest probably would have worked better. May give this a try soon, as I have a couple of pieces that I found significant scratches on, and may want to re-finish.

Dan

[Bill Wyko]

Thanks very much for the step by step. I'll try to put it to use soon so I can do a write up on it. I have a square platter I want to do in the near future. A beautiful piece of maple.

[Dan Kralemann]

I do a lot of vacuum work with veneers when I build humidors. I use the same vac for the chuck. I really appreciate all the info. Any place you guys can recommend to get the reverse chuck adapter? Possibly a SMC sponsor? That would have come in handy today actually. I'm finishing up another segmented turning, down to gluing the 2 halves together & removing the tenon tomorrow.

Best Wood Tools have two types of these adaptors. One is made totally of steel and the other is aluminum permanently attached to steel.


http://bestwoodtools.com/ (http://bestwoodtools.com/)