Thursday, December 2

Tray Tables - Panel Assemblies

Here it is Thursday and another week has almost slipped away.  First let me announce that as of December 31st 2010 Marie and I will be closing down the custom woodworking end of Smoky Mountain Woodworks.  Demand for custom work has fallen off so badly for so long that I must turn my attentions elsewhere to keep the bills paid.  We will continue to build the more popular items and offer them for sale, but I will no longer have the time to get full custom work done in a reasonable amount of time.  I will continue to work on the orders we have received until they are complete, but we will not accept new custom order after the end of the year.

We are working on a set of Cherry tray tables for Tina.
Next up is asset of walnut tray tables for Jacklyn.
Then a walnut steamer trunk for David (and completing the trailer)
Then a four tier stopper rack for Sue.
And Shelly wants a set of custom TV Tray Tables, if she can get PayPal to cooperate.

So, we were working on the tray panels for Tina’s tables. I had completed the glue-up and smoothing of the ribbon panels and roughed out the backer panels.  So now I need to glue the backer to the ribbon panel.  I do this with a strip of glue just down the middle of each.  Why do I need a backer, and why not glue the whole thing?  Both are related to the same issue; expansion.

Solid hardwoods will expand and contract across the grain with the raising and lowering of atmospheric humidity. Applying a finish slows it down, but does not prevent it.  Trying to glue the side rails to a panel that will move like this guarantees that the rails will pop loose.  So I use a thin plywood backer panel under the ribbon panel as a backbone to which I glue the rails.  The ribbon panel gets glued to the backer just down the middle so it can expand and contract without cracking. 

When I cut the parts to finished size, the ribbon panels are 1/8” narrower than the backer.  Then, when I glue them together I center the ribbon panel on the backer leaving 1/16” on each side as expansion space.  The groove in the rails hides this and holds the ribbon panel flat.  After gluing and positioning the two panels I apply a clamp at each end and use a heavy weight in the middle to apply pressure for a good bond.

Once the glue is dry it’s time to trim the panel assemblies to finished length.  When I glued up the ribbon panels I squared one end of the ribbon strips so it was fairly straight and even.  Both the ribbon panels and the backer panels are ½” longer than the finished dimension.  I start by trimming just a bit off the even end to be sure backer and ribbon panels are both perfectly flush, straight and square using my large cut-off sled.

Then I flip the panel over so the same side as before is against the fence and trim the other end to finished length.  Because I make so many of these, I have a lay-out mark and label on the sled in ink.

After cutting them to length, I check to be sure they’re square by measuring across both diagonals.  If the diagonals are equal, the panel is square.
I used to use 1/8” Baltic Birch Plywood for these backers, and the design is set up for that.  When Hurricane Katrina hit New Orleans the price on all forms of plywood skyrocketed and most forms of plywood became very scarce.  BBP was one of the worst for some reason.  To keep going I started using a thicker, cabinet grade plywood that became available again much sooner.  To get this thicker panel to fit into the slot in the rails, I need to cut a precisely sized rabbet around the edges of the bottom of the backer panel using the table saw equipped with a sacrificial fence (so I can cut right out to the edge of the panel).

The final step in this process is to sand the panel assemblies to smooth both faces and remove any small chips from the cherry face that occurred during surface planing.  I use the wide drum sander for this.  This requires very light passes at a slow feed rate, especially when I get into the finer grades of sandpaper.  It takes the better part of a day for this step alone.

When this is done I take a sanding block and put a very small chamfer (bevel) on the upper edge of the cherry ribbon panels, and the edges of the grooves in the tray rail parts.  This will help the parts slide together without snagging when we get to that point.

And that does it for the tray panel assembly.  Next I’ll cut the rail parts and fasten them in place.  But this day is almost over, and I need to get this much posted for you, so I’ll get to those tomorrow.  Please join me then!

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