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corbs
5th February 2012, 01:01 PM
Afternoon all,
Here's a little bowl I made out of Silk Tree which I got in this (http://www.woodworkforums.com/f8/silk-tree-albizia-147663/) thread yesterday. It's very green and just an experiment so please don't pay too much attention to my form or finish:rolleyes: but my question is this...

how do you finish turn the base on these types of bowls?

I turn the inside on a tennon and then mount in a set of bowl jaws to turn a foot or just remove the tennon but how do you do that with an edge like this? I don't really want to just sand the tennon off so I'm open to ideas from my learned colleagues:2tsup:

Corbs

brendan stemp
5th February 2012, 02:25 PM
Mount another bowl blank onto your lathe that is a suitable size. Turn this blank (or it could be a scrap lump of wood) to a shape of the outside of a bowl without a foot (ie a semi spherical shape) making sure it will fit snugly into the NE bowl you have turned. The closer this fit is the better. You then need to find something to act as padding between the bowl blank and the NE bowl and secure your NE bowl between the blank and your tail stock. This will hold the NE bowl onto the lathe sufficiently to finish the foot. You may need to spend a little bit of time getting the NE bowl running true just through trial and error. The only thing you will be left with is a little spiggot where the tail stock is. This can be carved and sanded off by hand. Hope this makes sense.

The only other alternative, I can think of, is a vacuum chuck but this is a lot more involved and would require you to have the vacuum chuck system in the first place.

corbs
6th February 2012, 06:07 PM
Thanks Brendan, I'm guessing this is what's referred to as a Jam Chuck. I haven't tried one before and am a little worried about how it actually holds while turning but will give it a go. It's only and experiment bowl so nothing to lose:rolleyes:

munruben
6th February 2012, 07:32 PM
That's a nice looking piece of timber you have there corbs.:2tsup:

corbs
6th February 2012, 10:09 PM
John, if all goes to plan I'm going to have an entire tree's worth of the stuff in the next 6-12 months :wink:

It seems to have a bad reputation for poor reactions when working dry though so might be busy green turning as much as I can if it goes to plan:rolleyes:

Sawdust Maker
7th February 2012, 08:58 AM
I think there's only one thing for it - You'll have to invest in a vacuum chuck

Paul39
7th February 2012, 12:59 PM
Very nice piece.

You could sand the bottom of the spigot flat or a bit concave, then hand sand any marks off the side of the spigot and any marks adjacent, and call the spigot a foot.

When I am doing something like that, I screw what will be the inside of the bowI to a faceplate. I make a recess or spigot, and turn and finish the outside of the bowl. Then I turn it around and mount on the chuck, expanding into the recess, or grabbing the spigot, which may be a foot with the bottom shaped for the chuck to grab.

I finish the inside, rim, and any of the outside not reached while against the faceplate, remove from the chuck, and hand finish any marks left by the chuck.

sjm
8th February 2012, 03:24 PM
Thanks Brendan, I'm guessing this is what's referred to as a Jam Chuck. I haven't tried one before and am a little worried about how it actually holds while turning but will give it a go. It's only and experiment bowl so nothing to lose:rolleyes:

Don't be afraid to wrap it up with masking tape. I use it all the time. I can never get my jamb chucks to be a perfect fit, so near enough is good enough, then I wrap it with tape.

corbs
8th February 2012, 06:16 PM
Will see how I go with a jam chuck down the track... I'm probably not going to have a chance to finish it for a while yet anyway. I like the masking tape idea too:2tsup:

jefferson
8th February 2012, 07:21 PM
Corbs,

The experts say to use electrical (not masking) tape when supporting a jam chuck. The electrical tape stretches and matches the shape of the wood so held. At least according to Vic Wood. And others.

Try it and see for yourself. Best idea is to make a tight-fitting jam chuck in the first place.

corbs
8th February 2012, 09:17 PM
Jefferson, I think the suggestion to use masking tape was to secure the bowl to the outside of the jam chuck but like the idea of electrical tape for the inside.

jefferson
8th February 2012, 09:57 PM
Corbs,

not sure what you mean. In the pic posted above, we see the use of masking tape on the outside of the work. I'm humbly suggesting that electical tape does a better job. Whatever works I guess.