Master Carpenter Video: How to Cut a Tenon for a Timber-Frame
Will Beemer shows how to cut the first half of a mortise-and-tenon joint—the quintessential timber-frame connection.
Timber-framer Will Beemer: In the previous video, we measured and marked the tenon. Now we’re going to cut the shoulder of the tenon by carefully cutting along our shoulder line. This is the most important line in our joint because it controls the dimensions of the building.
We’re going to be using power and hand tools. A lot of what we’re doing can be carried across all other aspects of woodworking.
For this particular tenon, I need to go down two inches. I’ll actually cut a little bit shorter than that and then pare down to the line with my chisel. Occasionally you will hear some timber-framers say to stay 1/16-in. away and then pare down to the line, but on end grain like this, that’s very difficult to do. It saves you a lot of work to learn to cut very accurately and cut right to the line the first time.
So now I’m going to remove these blocks of wood with a chisel. I’m going to start at the corner and take chips out to see if the grain is diving or rising. Whenever we’re removing gross material we want to have the bevel down on the chisel.
You’ll notice that I’m holding the chisel by the socket. In beating on the chisel with my hammer, the handle could loosen up and the chisel could drop off; by holding at the socket, I have a firm grip on it and it won’t drop away.
You can see how the grain is rising up here, so I should be safe beating on this material. I’ve gone a little bit below my line at the end, but the tenon will be tapered at the end so I’m OK.
Now we’re going to pare down to our line. I want to work in from my line on each side so I don’t blow out the far side and lose my line. Then I’ll have a little bevel around the perimeter that will be my gauge.
When I’m paring with the chisel, my forward hand is acting as a fence or guide. It’s gripping the chisel and acting as a pivot or a fulcrum. My aft hand is doing the pushing and steering of the chisel.
This surface of the tenon is laid out two inches down from my reference face. With the two-inch-wide leg of my framing square resting on the tenon, I can feel a little bit of the square still sticking up above the reference face, so I know go down. Sometimes it’s helpful to put a little lead on one edge of your square. And when you draw it back and forth, it will indicate where your high spots are. You can also use a combination square in conjunction with the framing square to locate high spots.
Now it’s time to move to the other side of the tenon. The first side was laid out from the reference face; the other side of the tenon is referenced off of the side we just cut.