Walnut winged bowl, and reverse chucking problem

[Moses Weisberg]

A friend of mine cut down a walnut tree and offered me some chunks, so I got straight to work.
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It still needs a few more coats of finish, but the main problem I'm having is with reverse chucking. I don't have a vacuum chuck, and the powers that be wouldn't be appreciative of another tool showing up in the house. My usual method involves a sort of jam chuck that matches the inside curve and a whole lot of shrinkwrap. When I make winged bowls out of beetle-kill pine, I generally don't have to worry about bark, but I'd hate to knock any of this off. I know I can jury-rig some sort of donut chuck, or just use the tailstock until the last nub, but am I missing something obvious or effective?

[Les Williams]

I am quite new to this but my thought is doughnut chuck with a pad like a jam chuck, it would keep the bark away from the back of the doughnut while you finish the foot.

Les

[Roger Chandler]

I would encourage you to stabilize the bark with the application of some thin CA glue on the layer [cambium] connecting the bark to the sap wood. Let it dry for about 15 minutes and then also use a piece of old mouse pad or something similar to cushion the jam chuck on the inside of the bowl...........use adequate tailstock pressure and you should be able to turn the tenon off and take it to a small nub, which you can part off with a chisel or small saw........then sand.

I have stabilized bark on NE bowls and they are still intact after two years........no issues.

[Thom Sturgill]

+1 to Roger's comment. Donut chucks are not NE friendly.

[Curt Fuller]

The jamb chuck you mentioned is what I use. But rather than shrink wrap it to hold it in place, I just put a piece of that rubber stuff they put under rugs to keep them from slipping between the bowl and the jamb chuck and then bring the tails stock up with just enough pressure to hold it in place. I then carefully turn the tenon offIt leaves a nub that I knock off with a chisel and then sand smooth. Not as slick as using a vacuum chuck but it works better than any other way I've tried.

[Robert Henrickson]

As Curt says, a jam chuck, pad, and tailstock. The pad can be almost anything -- I use carpet underpad or a disk cut from one of those foam drink can insulators (nice dense foam). I've also used foam from one of those big foam 'hands' sold in sports stadiums, a rag, and paper towels. One fellow turner has cut pieces from his old wet suit, another pieces from a mousepad.

[Mark Levitski]

Similar to the rest: I have a vac chuck but most of the time the voids make it impossible to use in these cases. I do use it for my jamb against the tailstock, but you can just make one yourself to put in the chuck jaws w/ some padding. Finish the bottom down to the nub, then trim off what's left, sand, and voila!

I do lots of these this way.

[Bernie Weishapl]

Before I had my vacuum chuck I used a donut chuck. To keep the bark off the chuck I used a 4" PVC coupler with a mouse pad. It work extremely well. I still use the donut chuck if there are voids in the piece.

[Thomas Canfield]

I do similar to what Curt and Robert said about using a jam chuck with some rubber shelf liner or similar for pad and the dimple in the tenon for alignment. You can do like Bernie said and use a 3" or 4" PVC coupling as a standoff if you need to gain some clearance for the natural edge. My jam chucks are usually made from glued up MDF that either are tapped using Beale threader for the drive or have a tenon to mount in the chuck. You will need to true up a PVC coupling or heavy pipe section if you use it for a spacer, but you can then form either tenon or grove to mount a jam chuck. This has worked on 19" bowls and long oval bowls. Just remember to keep enough nub diameter for strength and do not tighten tailstock to point of pushing nub though bottom (don't ask).

[Moses Weisberg]

Thanks for all the suggestions. I didn't get a chance to try them today, but I'll try another jam chuck tomorrow.

[Robert Henrickson]

It's easy enough to turn a jam chuck to whatever length or face width is needed. Any of that 'boring' wood that isn't 'nice enough' to make it onto the lathe and so is just sitting there will do -- everyone must have some wood that isn't interesting enough to turn but 'good enough' to not get discarded. I've accumulated a couple dozen jam chucks with diameters ranging from 2-5", lengths from 1-6", and faces ranging from slightly convex to strongly concave in the center. Some have been turned from the waste left in the chuck after the finished turning has been parted off.

[Pat Scott]

That's a nice bowl, but what you made is referred to as a Natural Edge Bowl, not a Winged Bowl (FYI).

This is more what a winged bowl looks like with the flat rim.
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[Moses Weisberg]

So I tried the jam chuck approach again, and had some decent results.
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I think this has inspired me to build a vacuum chuck.

[Thomas Canfield]

That looks like a jam good bottom. Why do you need a vacuum chuck?

[Moses Weisberg]

Thanks Pat.

I know people have different terminology, but I thought your picture was more of a saturn bowl, as the natural portion that extends below the rim as the rings on Saturn. The rule of thumb I've used has to do with the difference in height between the high and low points on the bark, or with the height vs the width. I'm curious what other people call each of these as well.

[Michael Mills]

All good suggestions and I would add to get rid of the bubble wrap because it is typically too soft and squishy and may allow the bowl to rock. I think you want something thin and strong to provide the friction. Other items in addition to those already mentioned would be a scrap of leather or the rubber jar openers from your kitchen.
How long the friction chuck is depends on the bowl depth and your lathes distance from the headstock. Most of mine are only ¾” stock with a short spigot but it is rare any bowl I make now is over 6” deep.
I think a flat or slightly concave end works much better than trying to match the curve of the bowl. If you are off much at all the bowl will just rock as it only has friction for a very small area in the center. By driving from the outside the surface area is greatly increased. I size mine by the base (maybe an inch diameter larger) so the main force of the heaviest cut is directly supported.