Mortise and Tenons and Sawing, OH MY!

After a substantial hiatus, I am back in the workshop again. The delays to my continuing work on this massive nested tables project started with being drafted by the boss to remodel my basement and then were topped off by me falling down the stairs and breaking my ankle. But all is reasonably well now, so off we go again on the project at hand.

It's tenon cutting time! This project is all about mortise and tenon joints. I counted them up and there are (I think) 68 mortise and tenon joints. I intend to cut them all by hand.

You can see my tenon cutting set up below. From the work on my prototype, it became apparent that marking all those tenon joints with a square and a marking knife would take a lifetime. The secret to speeding up the layout process is to have three marking gauges, pre-set to the depth, the width and the length of the mortise. Scribing the layout becomes much quicker. The 2 keys to accuracy are to be sure that all the rails are exactly the same dimensions, since the marking gauges depend on the piece for accuracy and to keep the gauges set without changing, throughout the project. If you try to reset your gauge, no matter how careful you are, you will inevitably introduce error. Ask me how I know this.

As you can see below, I have a knife gauge for cross grain work, a pin gauge for with-grain work and a mortise gauge, for making the two marks of the width of the tenon.


After scribing all the lines for a tenon, it is necessary to saw them with extreme precision. To accomplish this, you must be able to guide the saw against at least two scribe marks at all times. This becomes a very Zen moment as you adsorb the visual image of the saw tracking the scribe line in one plane while simultaneously adsorbing the image of the saw tracking in the other plane. It is essential to be completely in the moment and not let your brain run through random thoughts which will redirect your concentration. My thoughts invariably drift into a running monologue of describing what I am doing, as if I am writing my actions up for the blog (such is the fate of a woodworking blogger, I guess). This is a sure way to drift off track. Don't think about what you're doing, just do it!

I always start a cut by tracking the top of the tenon scribe mark, simultaneously with one side mark until I have cut across the whole tenon, simultaneously reaching the bottom of the tenon, but not down into the other side. Then I flip the piece over and cut tracking across the top and the other side until I have cut across the whole tenon, simultaneously reaching the bottom of the tenon, but not down into the other side. Then I come down vertically, using the kerf as a saw guide.

The last step is to cut the shoulder of the tenon, tracking the saw much the same way.

The saw must be held very loosely, so that you won't inadvertently use your muscles to mis-guide it. The traditional image of how tight to hold your saw is to imagine you are holding a baby bird. You don't want to crush it, but you don't want to let it get away.

This takes a lot of practice. Ask me how I know.

The next entry will be all about hand chopping mortises.