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Thinking about movement

1K views 14 replies 9 participants last post by  wormil 
#1 · (Edited by Moderator)
I'm looking replicate this clock. Should I worry about movement of the middle piece, which holds the clock? It's about a 4"x4" piece. Also, would you use M&T, dowels or countersunk screws to hold this in place?
Wood Clock Rectangle Material property Circle
 

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#2 ·
I'd use M&T. I know that is the usual response from folks on here for a joint, but I think it would be easier to do. Long stub tenon a little short of the overall length on the inside piece with corresponding mortice. You'd have a little play to make sure it is vertically centered.
 
#5 · (Edited by Moderator)
If that middle board is maple, and is 12" wide, I would allow for about 1/8" of seasonal movement in my design.

http://woodweb.com/cgi-bin/calculators/calc.pl

Looking at the pictured clock, the original designer allowed for movement by fastening the face board to the frame with through tenons that are probably not glued allowing the face to float in the frame. Dowels would allow for movement in the same way that the tenons do, screws might end up torn out (although it would probably not fall apart, rather the face would become loose.)

Edit to add: if you simply rotate the orientation of the grain on the face board by 90 degrees, the movement of the face board is not relevant. It won't be pushing on anything. Your joinery will be a little bit different, probably floating tenons (not through tenons) in a mortise that has a little space on either end.
 
#7 ·
With the grain oriented as pictured you will either have a gap to compensate for movement or a gap will appear depending on the materials moisture. Turn the material so the movement is not trying to push the sides apart.
 
#8 ·
An alternate thought here:
If the center piece is 4" there isn't going to be much movement.
I would use fake tenon caps on the outside and as A1Jim said, a groove to slide the maple into.

(BTW, a groove goes with the grain, a dado goes across the grain). I think. I could be wrong. Maybe.
 
#10 ·
I agree with rotating the center 90d and not having to worry about movement but in reality the movement across 4" will be irrelevant. You can use whatever joinery you want but the original appears to have through M&T or false M&T.
 
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