Console Table Build Part 5
In this week’s post, I cut the leg mortises and smooth the leg surfaces. When I created this video I did not own a Festool Domino (I do now), so I might have used that instead of my Inca slot mortiser to cut the mortises. The downside of the Domino is that it cuts a fixed-width mortise. It could be moved over to widen the initial mortise, but then layout becomes an issue due to its alignment feature focusing on the center of the mortise, not the outside edge. I think the slot mortiser is a better option.
Traditionally, the thickness of a tenon is 1/3 of the part thickness. This makes sense when both parts are the same thickness, for example, when making a cabinet door. That rule of thumb creates a joint in which both parts have roughly the same strength. Why would that be? One part (the one with the mortise) has twice as much material in it as the other; that seems counterintuitive. But, if you try to break that joint apart, you will find that despite the difference, the mortised part typically fails first, assuming the glue joint doesn’t fail.
How does it fail? The wood alongside the mortise splits along the grain. Despite there being twice the thickness, the tenon is mostly in tension along the grain and wood is very strong in that direction.
I learned this when I was teaching. At the end of each semester, students invariably left various project parts behind. There were occasionally some frame and panel doors, which we would break apart to salvage the parts, especially if it had a large solid wood panel. If you bang those on the ground, you quickly see what I have described above.
The leg/apron joint is different. The part with the mortise, the leg, is much thicker than the leg. In this case I would typically make the mortise and tenon 5/16″ thick. Why? Primarily due to the tooling; the 1/4″ spiral mortise bit vibrates too much, as you can see in the video. And why didn’t I use 5/16″ for this project? Good question; I don’t remember…
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