Biggest Mortise & Tenon Tabletop Ever!

As this is only my second Instructable, I read some of the tips. One said to have a Hook to capture the readers’ attention. Well, I thought the title could be the hook. It’s not the biggest table top ever, but I think it might be a table with one of the biggest mortise and tenons! Maybe? Read along while I build this big boy.

My tabletop started with a board that can only be described as MASSIVE. With an average width of 39 inches across and an impressive 15 feet long, the 2” thick board featured two live edges (flitch or boule sawn, meaning cut through the length of the tree) and not a single straight grain in the whole big board. I purchased this big board for a little over $1,000 (I had to save up) plus another $145 for freight from Gilmerwood Lumber. That might seem a bit much for some, but as this was a wedding present for my wife, I thought it worth it. And, when I did the math, the cost was a little over $19 a board foot – for highly figured Bubinga that is a very good deal. To truck it to me, I had it cut in 3 equal pieces of 5 feet long each. And each piece weighed several hundred pounds!

The first pic shows what the wood looks like with a finish. This rare figure is often called kewazinga bubinga, cloud figure bubinga for those of us that can’t pronounce the first name.

Tablesaw
Router
Hand planer
Bandsaw

One Really Big Board of your favorite wood

As with all my projects, I did lots of research to try to figure out how I wanted to do my table top. One of the main things I kept running into regarding a table top is End Grain. And I didn’t want any. And then I came across a term called bread board ends. That is when you attach a board piece perpendicular to the each end of your table top so that the nicer edge grain is showing at the end of your table.

But first, I had to put two tabletop pieces together so that my tabletop would be a good dining table size. Now, I thought about having a live edge on my dining table, but I realize I didn’t want food and tableware to roll off the table. So, I trued each edge so that if there was any live edge it would be towards the bottom, not the top. Because this was so big, I took two of the big boards to my local lumber store and had them use their big edger to do the honors.

Now, I took my router and ran a large rabbit cut down the length of each inside board. Then, using poplar I made it a 5 foot long inch and a half wide spline. Then, I glued and clamped the two big boards together with the spline. The second pic shows them together now. Notice that I arranged it so that the sapwood formed a sort of stripe down the middle of the board!

With the board together now, the width is about 4 feet wide. Now, for the biggest mortise and tenons ever!

In the first pic, it shows the tenon completed. This part wasn’t really that hard. I clamped a wood rail parallel to the end and used a router with a big straight bit and cut the tenon. But, I had to do it slowly. So I would cut a little off on one side the whole length, then flip the board over and cut some more. Then, flip the board again and start over. But, this was Exhausting because it was so heavy. This way the tenon would be centered on the piece.

Now, for one big mortise. It is actually a blind cut mortise.

Disclaimer: What I am about to describe is not for the faint of heart...

In order to saw this blind cut mortise, I had to teach myself and measure how to cut on my tablesaw without actually seeing the blade or physically measuring the height of the blade. So, I did some test cuts where I measured how high the table saw blade rose for each half turn of the wheel. Then, I did some test cuts where I measured where the blade would be at the bottom of the arc where it meets the tablesaw surface. I put marks on the tablesaw surface for my start and and stopping points. Now I was ready to cut the Mortise. I placed my 2 inch thick Wenge on its edge and positioned it on the tablesaw. With the table saw blade just below the surface, I turned the machine on. Then, I carefully raised the dado blade to the height that I had calculated. Then, I slowly push the board through and stopped where I had measured. I quickly turned the machine off and waited for it to slow and stop. Voila, the mortise is done. See the second pic.

I realized then, though, that my straight tenon wouldn’t fit because my inside mortise had a curve from the dado blade. So, I had to shave and create a small arc at each end of the tenon.

I used a hand planer to shave the tenon a little to make a nice fit.

To add a little flair, I cut a piece of Bubinga with a double curved arc and with a router cut a channel in the Wenge and fit the piece in. I also drew a curve in the Wenge and cut it on my bandsaw. Then, I glued the Wenge in and from below I tapped in some blind pins so that you couldn’t see the attachment from the top.

Alas, this project was never finished with legs. My now wife passed suddenly not long after the tabletop was finished. But these pictures at least are a testament to a well inspired project.

I’d like to enter this in the current furniture contest, but not for any ranking. But more to inspire others with how powerful a little imagination can be to create and contribute...