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post #5 of (permalink) Old 06-26-2016, 10:05 PM
Cherryville Chuck
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Join Date: Sep 2010
Country: Canada
First Name: Charles
Posts: 16,385

what are your fastening methods???
why are you doing this in sections.....

rip a piece ½-¾'' (or more if you can) ply the width and length of the assembled corner piece...
careful on the fit..
glue the sections to the ply.. use a 23GA pinner to pin the ply to the molding but no larger...
glue the assembly to the face frames and mechanically fasten through the back w/ screws being careful to screw into the ply only..
add blocks to add to thickness for the screws if you can...

the splits are because of the early or spring wood of the pieces...
and it doesn't tolerate mechanical fastening w/o preventive measures...

Tom all of that is true. What is cracking your wood is too much stress being put on it. I fully agree with Stick when he says to bridge the corner with ply and then attach the round piece to the ply. Let the ply handle the stress. It's better suited for the job. One of the other possibilities is that the wood may have started with too much moisture content and has dried since you started. Even if that isn't the cause now, it could be the cause of a later failure. Wood cells build up from the center of a tree in layers. Each layer of cells is longer than the previous one so that the outer layers shrink more when it dries than the inner layers. This will cause cracks and breaks if not allowed to move freely.

If you do like Stick suggests I would only attach the piece at its center but it could be attached very firmly if only there. That would allow movement at either end without causing the piece to crack. I personally would try to either rabbet or mortise the ends of your corner pieces into either side at least 1/8". That way if there is shrinkage there won't be a visible gap at the ends where they meet the sides.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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