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Large segmented blank for a Tondo frame

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Adam W.

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I've made one of these segmented blanks for a Tondo frame that I want to turn. It's just over 2' in diameter, so it'll be hanging off the outboard end of my machine.

I thought it was a great idea at the time, until I came to the logistics part of how to get it mounted on the machine.

Any Ideas would be helpful for a safe, no budget mounting arrangement. I have a VM 120 chuck and an outboard tool rest and a face plate which isn't that big.


IMG_4601.JPG
 
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Chris152

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Will one side (the back) be flat/ unturned? If so, you could screw that side to a ply disc, which is attached to the face plate, then turn the outward-facing side? Just make sure you don't hit the screws (coming from the back) while turning.
(Alternatively, try hot glue to attach the ring?)
 

Adam W.

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Chris, one side is flat and I'll cut the rebate for the sight edge by hand, then I'll carve it. I like the sound of the hot glue option, will it be easy to remove it from the ply, as it's a large surface area. I don't want to have to cut it off, as there will be a fairly small covetto moulding on the outside edge and I'll run the risk of damaging it.
 
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Chris152

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I've not tried the hot glue method but know turners use it for attaching tenons to the back of pieces where needed. I've turned a number of odd-shape things using the screw-on method that wouldn't attach any other way, one maybe as large as your ring. I guess the answer might be to not apply glue all over, but a series of strips that follow the radius, maybe 6" apart? If there's any problem releasing, gentle treatment with a hair dryer to soften the glue?
As you can see, I'm not much help with hot glue!
 

Phil Pascoe

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Just remember if you're not used to using hot melt that you don't want to get it between the workpiece and the ply, or if you do to include spacers (pennies, washers ... )so you can get a heated knife between them otherwise you will likely damage the piece removing it . It's easiest just to go around the periphery so you can whack a chisel through it when you're finished.
 

Droogs

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Perhaps try the maskingtape and supperglue trick on it (as I guess it wont be going at a high rpm), might make it easier to seperate later.
 

paulrbarnard

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Give it has a nicely defined inner shape perhaps you could make an in-fill piece and wedge or glue it in. You could make it slightly tapered so you can push it into your ring really tightly from either side.
This would let you turn all the outside and all but the center of the inner. To finish the inside hot gluing the almost finished ring to a flat disk would get you the final step.
 

Adam W.

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Thanks for the advice so far.

Has anyone tried mounting stuff like this with a paper layer between the glued surfaces ?

@paulrbarnard Do you mean like a big jam chuck ?
 

Phil Pascoe

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I think I would be hesitant to use a paper joint on something that wasn't a single piece - they can be sods to get apart sometimes, especially on something that size.
 

Adam W.

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Perhaps try the maskingtape and supperglue trick on it (as I guess it wont be going at a high rpm), might make it easier to seperate later.
You are going to have to explain that to me in words of one syllable or less.
 

Droogs

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Cover the back of the piece and the backing board with wide masking tape and then coat one of them in superglue and the other in applicator and stick 'em together. They will stay together while working on them and then come apart easy enough as one side of the masking tape will give way. if good enough for cnc should do for you

 

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Obviously the vid is just to show the principle, you won't need to be so fastidious with wood
 

Adam W.

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Adam,
Excuse my ignorance, but what’s a Tondo frame?
D
It's one of these, traditionally from Northern Italy in about 1500...

lorenzo di Credi.jpg


Here's a primer.....

 

Adam W.

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Here's an 8" tiddler with a guilloché motif.

I turned this in green oak as an experiment and I'll clean up the carving, gild it and insert a small silvered piece of glass as a mirror when it's dry. These are from 1500 Firenze and were turned whilst green on a pole lathe.


IMG_0018.JPG
 

Linus

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Another option would possibly be a Longworth chuck in the central hole. It looks fairly symmetrical to me as you have 8 segments .
 

Neil Lawton

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I've just made a station clock for a museum. Two rings were needed one at 24 1/2" diameter,1 14" thick, and one slightly smaller at 2" thick. I mounted them through the back of what would eventually become the real mounting holes so I had room to work without hitting screws. Both held in a 6" chuck mounting faceplate ring.
 

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If you can get away with using screws to fix it onto a plywood disc ,it’s better than the glue gun option,you have to be fast in application and apply even pressure to get a nice flat bedding,otherwise you risk the separation,especially on a disc that size
Take it your lathe can be slowed down to take minimize the momentum your disc will create?
another option is to use a router.
 

Adam W.

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Yep, I think screws on a disc would be the best option, as I can screw into each segment because I'm chicken.

The lathe goes down to 10 rpm both ways, so I don't think it'll be a problem. A router is a no go, as the size of the moulding is huge and I'm not buying a cutter that large.

That's why I bought the lathe.
 
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