Replies

1. 
   CStanford_ | Feb 14, 2001 07:19pm | #1

   *
   No glue. Use 4d finishing nails (or cut finishing nails/brads for period authenticity, I prefer a cut brad about 1 1/4" long) to nail the backboards into the top, the bottom, and the middle fixed shelf. These nails/brads are small enough to flex with the movement of the backboards and the case in general. Screws are o.k. but use a thin shanked woodscrew and only use one screw at the top, middle, and bottom of each backboard. Consider elongating the top of the screw hole to allow for some movement, although using a 4d finishing nail eliminates all the pomp and circumstance.

   I typically cut rabbets for the backboards, a tongue and groove with a "v" or a bead looks nice too. I butt them together tight. Had more problems with shrinkage over the years than expansion.

1. 
   Danford_C._Jennings | Feb 14, 2001 07:38pm | #2

   *DL,FWIW, if using 4/4 or 3/4 stock, my approach would to be to reduce the stock widths to at least 3" to reduce cupping, mill out the tongue and grooves, glue up by alternating the growth rings (up,down), make the feature cuts very shallow, and let the panel "float". Most of the movement will be accross the grain and can be calculated from tables found in numurous woodworking books, you will however have to know the moisture content of your stock for these calculations to be meaningful as well as the relative humidity of your shop and location of the piece. Charles' approach is a good one too. A lot depends on the look and style of the piece.Dano

1. 
   Madison's_dad | Feb 14, 2001 07:41pm | #3

   *I would glue the 6" boards together with a tongue and groove then I would set the back in a loose dado with 1/4" of expansion room. the only screw / nail I would use would be in the center board in to a fixed shelf. How about only grooving every 6" just a thought I seam to be in to wide boards lately I just glued up a panel with 6 1/2" boards in VG Fir. Don't for get to make the out side boards bigger so the spacing looks right :-)Chrisjust read dano's I like the growth ring to run the same way so the back moves as one IE bows out or in I like in it seems to help keep the back tight to the shelves. But the 3" boards is probably a good idea if the grain is at all wiggly (a technical term)

1. 
   CStanford_ | Feb 14, 2001 09:39pm | #4

   *There are a lot of ways to skin a cat, but I would not glue a tongue and groove joint. The point behind the joint is to allow expansion and contraction while maintaining coverage (no visible gaps for daylight) between boards. Woodworkers have used various methods like running beads and various profiles where to boards meet to completely hide the gaps that open and close over the seasons.Your Mahogany is fairly unlikely to cup noticeably at 6" widths, at least in my experience. Other woods like Oak, Maple, and Cherry might present a problem in 6" widths. However, ripping down to 3" as Dano suggested would virtually guarantee no noticeable cup in Mahogany.In the years I've been woodworking, I've never once seen a solid wood case back glued in any way. The only type back one would glue successfully would be a plywood, or other sheet good back.

1. 
   Madison's_dad | Feb 14, 2001 11:29pm | #5

   *My use of the tongue and groove is simply for alignment and added glue surface. The finished panel should be know diferant than a table top made with 6" boards. But never glue the back to the case. (-:Chris