Dining/Game Table - #8 Design Discussions, Humidity Driven Expansion & Contraction, Attaching First Rail to Leg

In between the woodworking I did three more stain samples.  We seem to have the color right but it is still a bit light.  For these samples I increased the dye to alcohol ratio by 50% and by 100% on the closest mix and by 50% on the second closest.  The results are not quite what I thought they would be in that doubling the amount of dye in the solution did not look to have a corresponding darkening effect.  I may be reaching the limit of the dyes.  I could add black but think that would screw up the color.  Once my son gets the samples we will discuss and see if one of the samples will work.

Stain Tests

In  the beginning we started with a poker table playing surface.  In time the view of the playing surface function has evolved and so has the specifications.  Board game tables and poker tables have two slightly different criteria and since this is primarily going be a board game table that is what we will focus on.  Our criteria boiled down to these items: 

1. A slick smooth surface is not desirable, something with a little tooth is preferable.  More toward a pool table felt rather than the casino speed cloth. 
2. Something that will not permanently deform when loaded and left for a week (long term game or weekend to weekend playing).  The pad needs a memory to spring back to original flat surface.
3. The pad needs to be flexible enough to deform when pushed with your finger to allow pick-up of items but not so soft as to deform when you have stack of tokens on it.
4. A closed cell material is preferable to an open cell so that it will not absorb anything spilled on it.
5. The playing surface needs to be cleanable to remove the inevitable soiling.
6. The playing surface and underlying pad need to be replaceable at a later date. 

 As I told my son when we started, with custom furniture the good news is you can have whatever you want.  The bad news is you can have whatever you want, but you have to decide exactly you want.  I think he has sorted through the myriad of options for the pad/playing surface and is close to a decision.  I include our discussion because the pad and playing surface will drive the final design of the support structure for the playing surface.  It’s not critical in the sequence of construction, at least not for a couple of weeks.  Here is one of two generic support assemblies I am considering using.

Possible Structural Playing Surface Support System

After letting the table rails set for a few days I checked them and good news they were flat and straight.  The flattened cupped pieces for the arm rest are flat but I want to give them plenty of time to make sure they are stable. 

I have given the connection between the legs and the rails quite a bit of thought because there can be a lot of stress on that joint.  The simplest way would be to glue the leg to the rail and reinforce with 4 or 5 wood screws.  Given the size of the rail and the leg I would have a little over 14 square inches of glue area and that’s quite a bit.  Adding wood screws to reinforce the joint would make it really strong.  Unfortunately, that approach ignores that the grain in the leg runs one way and the grain in the rail is 90 degrees to that.  I am concerned with the cross grain expansion and contraction due to humidity changes.  I have seen all sorts of examples in antiques where humidity driven width changes causes table tops to split, chest of drawers sides to split, trim that works loose and other problems where two pieces of wood fight each other and eventually one splits, breaks or comes loose.

Rather than be in the dark and make a guess on the amount of expansion I did some research and found that the potential expansion with the humidity difference between New Mexico and Arkansas could be almost 1/8” across the 3¾” rail to leg connection.  I know from sad experience what building something in the dry desert and taking it to a more humid location can do.  Once about 6 months after I delivered a hall cabinet to Arkansas one set of doors would not close.  I had the tolerances a little too tight and in the summer humidity there it grew just enough to not close.  It really surprised me as there was only about 2” of cross grain wood in each of the door stiles.  Anyway, I had to take the door back to New Mexico, trim a sixteenth off one edge and refinish.   No problem since then.  Now I know that with 4 stiles the total movement could be about an 1/8”.

After a lot of thought I decided to limit the glue area to a 2” square patch in the center of the connection leaving the rest of the joint freedom to move with humidity changes.  This will limit movement change to less than 1/16”.  I will also add 4 wood screws between the leg and each rail.  This should give me a pretty strong joint.

Layout of Screw Locations for Leg to Rail Connection

Now that I had decided what to do I just had to cut the rails to the correct width and length then lay out where the screws and the glue will go.  To reduce the chance of errors and speed things up I use a couple of marking gauges and adjustable squares set to the distances I needed.  Using them all the layout lines end up the same.

Layout Tools

Because the project will be broken down flat for delivery I mark which piece is which along with reference notes so when I go to put it together I put the right piece in the right place.

Reference Noted & Marked Screw Locations

Next step is to drill pilot holes for the screws, square the leg to the rail and clamp them together.

Drilled Screw Holes & Squaring Legs to Rail

In  the image below you can see the screw that I will use.  It is a round head Kreg® pocket screw.  The small block of wood is the same thickness as the rail.  It’s always good to check screw length because driving a too long screw and having it come out the exposed side is not a good plan.  I use the Kreg® screws because they have a round head with a flat bearing surface against the wood.  Combined with an oversized pilot hole that allows the wood to move around the screw.  A flat head screw’s conical head can lock the pieces in place restricting movement.  It can also act like a wedge and split the wood if you are close to the edge.  Since I had that situation in a few places I wanted to minimize the risk.  On the left side of the leg the square is where the glue will go during final assembly. 

Ready to Install Screws

Once the screws are driven home the connection between this long rail and leg is solid.  I am not worried about the screws and glue holding the eventual dining table load since the rails are supported by the leg.

Rail Screwed to Leg

Next Up – Installing the Remaining Rails & Starting Playing Surface Structure