Replies

1. 
   frenchy | Jun 14, 2006 08:29am | #1

   hdgis1

     I'm guessing so this isn't perfect but should help you get near to what you seek..

     First  You are trying to replace age old experience with technical data.. The mahogany pieces built centuries ago weren't built in A/C shops yet the pieces go from auction houses to A/C houses without a problem.

     A/C dries things out,, a lot!  While a shop without A/C will have a great deal of humidity..

    Do you have a moisture meter?

     Take measurements and that should show you just how much.. My books are packed away but the percentage of movement of various woods is pretty well known..

        You just said Mahogany.. What Kind?

    Columbian, African, Philippine?     adjust according to moisture readings and wood type..

   readjust according the way the wood was cut.    Quarter sawn, Plane sawn, burls flame other figured wood..

2. 
   JohnWW | Jun 14, 2006 05:19pm | #2

   The wood will move forever as the seasons change and the piece gets moved to different homes and different climates over the years.  Good technical design of the piece is the only way to solve the problems from this type of wood movement.

   The point to acclimating the wood before the work is started is to get the wood's moisture content in balance with the humidity in your shop so that the wood doesn't move as you are doing the joinery. 

   So the short answer is that the wood should be stickered up in your shop at least a few weeks before you start doing any work on it, other than possibly rough cutting the stock to oversize dimensions to make it easier to handle and stack.

   John White, Shop Manager, Fine Woodworking Magazine 

1. 
   hdgis1 | Jun 14, 2006 08:07pm | #3

   Yes that makes sense. However, how can one best 'design' a dovetailed case so that two different woods move the same amount?

1. 
   JohnWW | Jun 14, 2006 10:17pm | #4

   Two different woods may still have similar enough rates of movement that the joinery won't be subject to a lot of stress.  Wood also has a certain amount of give so that a slight mismatch in movement won't lead to problems.  The devil is in the details.  If you want specific design advice I would need more information: wood species, grain orientation, and dimensions for starters, along with the type of joinery you were going to use.

   John White, Shop Manager, Fine Woodworking Magazine 

2. 
   SteveSchoene | Jun 14, 2006 10:19pm | #5

   The primary worry is during construction--if dovetails are cut at one moisture level and not joined until later when they have changed to different moisture levels there could be a fitting problem.  That's why the aclimatization to shop humidity is recommended.  But once joined, the differential movement of primary and secondary woods hasn't seemed to be a problem over the hundreds of years that the dovetail construction has held up.  And, if you are using a wood with a relatively large shrinkage for the primary wood--hard maple, for example--then you might want to choose a secondary wood with relatively more shrinkage--oak or poplar versus eastern white pine.  But frankly I doubt it makes much difference--this movement differential is more likely to compress a few outer tails, not split boards, or loosen joints, I wouldn't think.