Thread: Ahhhhh Noooooooooo

Hmmmmm I've got a box with a similar problem stashed away in a cupboard somewhere - it's been there about 8 years now

But seriously, from my experience you are never going to keep it in place with glue. I reckon you'll need to 're-segment' at least that join and flatten it so there's no tension - for the time being.

I knew there was a good reason I don't do segmented stuff

5mm's a fair bit, personally i'd slice it right through the middle with a bandsaw and take a very light pass with a jointer then reglue.

good luck

joez

Ouch!

I think I'd go all industrial on this one.

Firstly, I'd turn a round disk of MDF and glue it to the face, to act as a backer. Then I'd run it through a TS with a thin kerf blade, ripping along the failed joint with the MDF facing down. Glue the two halves back together - possibly inserting a thin strip the same thickness as the kerf. Or maybe not. Then turn it to the next joint and rip and glue again.

Repeated until all are matched again.

Finally, of course, remounting and turning away the MDF.

Or maybe if you can find somebody handy with a Bandit strapping set up, you might be able to pull it together and as for glue perhaps only epoxy will have the strength. Leave it clamped for several days

http://www.westernex.com.au/products...duct+Search=38

Similar to what joez said. Bandsaw through the center (including the bad joint of course). Sand the cut surfaces smooth and flat, removing any of the existing ebony divide, and glue in a new ebony divide. After cutting and sanding the cut surfaces flat, might want to let the two pieces sit for a couple weeks and see if the sanded surfaces remain flat. Beautiful piece, BTW.

Originally Posted by Texian

Similar to what joez said. Bandsaw through the center (including the bad joint of course). Sand the cut surfaces smooth and flat, removing any of the existing ebony divide, and glue in a new ebony divide. After cutting and sanding the cut surfaces flat, might want to let the two pieces sit for a couple weeks and see if the sanded surfaces remain flat. Beautiful piece, BTW.

That's the way I would do it. Good luck with it Neil, It's a lovely piece.

Thanks for the ideas guys, certainly gives me a way forward.

I'll use Skew's idea of glueing a backer to the front, that is still unturned, to give me a flat reference surface for the reglue. I'll then rip through the joint with the bandsaw, sand off the ebony divides, then reglue with new divides.

Hopefully it will remain flat and round, I don't have enough timber left to play with, other joints may then fail.

I must admit I'm a bit worried taking it to Melbourne, although it will be finished then. I was going to finish with paraffin oil all over, but now thinking of using the oil on the cutting board, and use Glass Coat on the platter to completely seal it.

Thoughts?

Thanks again

Hi Neil,

This is often a problem with flat segmented platters. The only failures I have had have been with these . Where you have wide flat segments, the problems with wood movement are exaggerated. Usually, the problem lies with shrinkage, which gives a failure in the centre. In your case, I would imagine it was increasing humidity, and expansion which resulted in a rim failure. If you can repair, (and the advice regarding ripping in half along the failure line seems good), the drier Melbourne climate may then "suit" the piece more???

A solution from Cox's book, "Beyond Woodturning", is to turn a recess into the base, (as big around as the design allows), and inset a glued in inert piece, (preferably ply). Because of the large flat glueing area, as opposed to the small segment surfaces, it is better able to resist the stresses from wood movement. Where discussed, it was speciffically directed at the shrinkage failure I described above. I am not sure how effective it would be for your rim failure mode.

FWIW,

regards

I think the problem stemmed from the dry cold period we have had, it was quite damp and humid when I glued it up, so shrinkage being the problem. Yesterday I found the gap had closed back up slightly to around 2mm, so managed to glue it up again without resawing it, clamping in the bowl jaws to clode the gap completely.

I am quite worried about the difference in Melb and was considering reinforcing the edge to "hold" it. I'm thinking of cutting a small rebate in the bottom, epoxy in a stainless steel strand, then cover with some coloured resin. All this while it is still clamped in the bowl jaws.

Neil,

I've not got into segmented turning, but have done some thinking on the topic. My view is that even if you used the same wood splayed out like you have, you would have separation problems. The wider the wedge, the more it will expand and contract at the edge than the centre. Glue will not hold, ever. Not unless you do the math on the expansion / contraction rates with changes in humidity and the boards are all from the same stick of wood and you get the angles just right.

Segmented bowls limit the problem as the width of the side grain ends up small. Not so for platters.

Either way, you must use timbers that expand and contract on the same tangential plane. If not, you will have problems that you cannot fix. As you have found out.

In ancient times, stone masons used to drill holes in rock, insert a timber tenon, then wet it. And of course, the stone cracked. Such is the pressure of expanding wood.

It's the same rule for all woodworking, not only turning.

IMHO of course.

Originally Posted by jefferson

Neil,

I've not got into segmented turning, but have done some thinking on the topic. My view is that even if you used the same wood splayed out like you have, you would have separation problems. The wider the wedge, the more it will expand and contract at the edge than the centre. Glue will not hold, ever. Not unless you do the math on the expansion / contraction rates with changes in humidity and the boards are all from the same stick of wood and you get the angles just right.

Segmented bowls limit the problem as the width of the side grain ends up small. Not so for platters.

Either way, you must use timbers that expand and contract on the same tangential plane. If not, you will have problems that you cannot fix. As you have found out.

In ancient times, stone masons used to drill holes in rock, insert a timber tenon, then wet it. And of course, the stone cracked. Such is the pressure of expanding wood.

It's the same rule for all woodworking, not only turning.

IMHO of course.

Jeff,

the problem is not just to do with the movement being similar. It is more the difference in movement across and along the grain. It is the same issue which causes the opening up of mitre joints in the middle, (shrinkage) or at the corner, (expansion). While you can get away with it in narrow section, as in bowls/vases, the problem is magnified in platters.

While I have not tried the "inset" solution I mentioned above, it is reputed to solve the problem, by adding a large side-grain gluing surface in addition to the small endgrain joints typical in segmenting, and hopefully "forcing" the timber to conform to the dimensionally stable ply etc.

I'll try it when I get around to doing a segmented platter again.

regards

regards

Yep, I concluded I would continue to have problems, so after regluing the joint I have cast a 3mm SS strand (what I had) into a rebate with black resin whilst still in the jaws. The rebate is angled towards the centre from the outside on the base, to avoid the strand and resin from popping out when under stress. The SS strand should more than cope with the forces induced from the temperature/shrinkage etc.

Can only hope it all works

Thats got to suck! hope your fix works Neil!