Mahogany movment


Ronn W
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I am bout to glue up the top for a 26" x 12" table.  I am using African Mahogany purchase from cabinet shop (good stuff) The end grain on a board laid flat on the workbench is straight upa nd down (quarter sawn or may be even rift cut.  I was planing to border the top with a shaped moulding similar to what one would see around the edges of a Queen Anne tes table. (mitered at the corners)  Then it occured to me that I could have movement problems witht he mouldings at the ends of the table.  I think I have 3 options.

1.  Just build it and and hope that 12" of rift cut mahogany won't move enough to noticably cause problem at the miters.  It is my understanding that this Species is quite stable to begin with and rift cut is even better.

2.  Glue the front 3" of the moulding on the ends and pin nail near the back corners to allow movement and let the back miters move.

3.  Design the moulding so that there is an intentional 1" or so gap in the moulding in the middle of the 12" long moulding on each end of the table.  See sketch.

How would you do it?

 

Capture.JPG.47fe68892c0844855b22f89af396d4d7.JPG

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Framing solid wood is always a cautionary tale.  As the panel gets wider the concern increases.  It looks like you are going for a dish effect (outer edge taller than the table surface).  Is the 26" the long grain direction?   I avoid framing solid panels but, even in my breadboards I use something like your option #2.  I attach the front to keep that look constant throughout the seasons and allow the rear to move.  Minnesota has actual seasons so I imagine you get decent humidity swings.  Using option #2 you could see gaps of up to 1/8" at the rear miter joint.  If this will pass muster I would go that way.  For more peace of mind I would go with your #3 or simply profile the edge.  Both make a significant change to the look of the piece. JMHO ;-)

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The wood shrinkage calculator at WoodWeb says that species should shrink or expand by 1/16" with a 6% change in MC.

I think "Old-Timers" would have simply nailed the molding on, and trusted the flexibility of the nailed joint to keep the panel from doing any real damage. And nails can be replaced as needed.

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I have alternate suggestions. This is from an uninformed perspective. In viewing images of queen Anne pieces the tops appear to be solid wood with the profile cut into the edge. The top appears to be veneered giving the look of a mitered frame but not actually enclosing the top in a frame.

I see your molding appears to go above the top surface. A rabbet may work and apply the frame like you would a breadboard end with  pegged tenons? This could leave the sides able to expand and contract within the frame. Or make the top a frame and panel and cut a tongue that would interface with a groove on the frame. The tongue would be the upper portion of the top such that a gap is not produced.

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The other observation is to do a captured panel. providing a small gap surrounding the panel for expansion and contraction.

Part of me thinks they didn't do anything to consider wood movement based on the comments on this piece. https://www.invaluable.com/auction-lot/queen-anne-cherrywood-tea-table-new-england-lat-8754abb90f

 

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On 12/2/2021 at 6:32 PM, Coop said:

When you get in your seventies, it’s less of a concern as well! 

Yeah, I have been noticing that about a lot of things.

I have decided to use  option 3 with less of a gap than in the sketch to minimize the visible end grain of the table top. 

Thanks, all.

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