John is working on completing the Trestle Table
I used my tax stimulus money to buy a flat screen TV. The problem is that I have to walk past the
TV to get to the shop. So I was enjoying
TV in all it flatness when I saw the end of the table sticking out of the
shop. It seemed to beckon me as it lay
there cupped and in need of work. But, I
am a man, so I grabbed the remote and ignored it. Now I am back at it and dealing with the cup
across the width of the table.
The trestle table top (say that three times fast!) is made from two book matched cherry
boards. They finished out at 103 inches
long and 13 inches wide. I added a
middle board to the two book matched pieces to get a final width of 31
inches. This was going to be a kitchen
table but with the length, it goes into the living room. I could have cut the top…only kidding, I
would never cut boards like that. Would
you?
The thickness of the top is just under ¾ inch so it flattens
when forced without that nasty cracking noise that indicates you just learned
another lesson. The cup, which you can
see in the picture, is a ¼ inch. For the
picture I clamped on side of the table flat so you can see the total cup that I
needed to flatten.

Now the bread board ends create a cross grain situation and
wood movement becomes an issue. I like wood
movement! There I said it. I like
feeling the non flush edges that arrive with the seasons. My friend has a table from the great
Christian Becksvoort and he insisted on bread board ends. He can feel with his fingers that the top has
moved. I like these oddities and have
added divots and ridges under the arms of chairs for a person to finger when sitting. These subtle aspects humanize a piece.
First thing to do was to determine the size and layout of the
tennons. Since we have a cross grain
situation I am only going to glue the middle tennon,. I decided on three tennons because it gives
me a middle. I think five tennons would
work if the width would accommodate it.
I also used a stub tennon on the entire width of the top. This stub is 3/8 inch in length. The thickness of all tennons is a ¼
inch. A rule of thumb in deciding the
widths of the tennons is the have all of them equal ½ the total width of the
table. For me, I made them 5 inches for
a total tennon width of 15 inches. It is
also important to have enough wood at the ends of the bread boards so I started
the tennons ¾ inch in from the edge. I
marked the mortis locations from the tennons.
I increased the mortis for the end tennons by 1/8 inch on each side to
allow for movement.

One
thing about mortis and tennons that is finally sinking in is that they are
related.
What you do to one has an
effect on the other.
For example, my first
idea was a tennon that looked like the tongue from the Rolling Stones symbol.
From the tennons’ perspective I was right,
but what about the mortis?
Chris pointed
out that the walls of the mortis are just as important as the tennon.
If the walls are too thin, the tennon will
crack them and that old sinking feeling arrives.
At least this time I learned a lesson
without cutting wood!
Regards
John