On to the last splicing joint from this short series of joinery models. This is the ari-tsugi (蟻継ぎ) or dovetail splicing joint. Overall the form of this one is probably the most familiar, at least to anyone who has some experience with dovetail joints, and cutout is likewise fairly straightforward.
After laying out the joint I started by cutting the female half of the joint. When it comes to typical dovetail joints that you might use to join the boards of a cabinet, you have the option to cut the pins or tails first, depending on your personal preference. A joint like this ari-tsugi on the other hand is a bit different, and if you ask me it makes sense to start with the receiving end of the joint first. I do the same with mortise and tenon joints, cutting mortises first then sizing the tenons to fit. Cutting joinery in that order can save you in the event you mess up the layout, or if you overcut the receiving end of the joint you still have a chance to modify the size of the male half of the joint. And I find it much easier to match a tenon to a mortise than the other way around. The same applies here.
So on to the cutout. I started by hand sawing along the inside edge of the receiving dovetail.
Then proceeded to chop out the joint using a combination of chisels, laminate trimmer, and finally a paring block for shaving the end of the joint clean and square.
Looking at the joint from the bottom side, and you can see there’s a small recess for receiving a stub tenon. The first step for cutting out that little recess was to cut just inside the layout lines with a handsaw.
To clean up the recess I used a laminate trimmer.
At this point I decided to shift gears and start cutting out the male part of the joint. The image below shows the male half of the joint after hand sawing the outer edges of the dovetail. The finished dovetail will only be half the height of the material, but I layed out and cut through the full thickness of the piece. Cutting through a wider section can make for a more accurate saw cut since you have a longer layout line to follow.
Next I knocked out the shoulder cuts at the tablesaw.
And while I was at the tablesaw I remembered I had one more cut to make on the female part of the joint. The upper shoulder of the female part of the joint gets cut back creating a seat which will engage with a matching cut on the other half.
Jumping ahead a bit (sorry forgot to take pictures) you can see the male dovetail after cutting away the lower half, in addition to cutting out a set of recesses which establish the stub tenon. And with that this joint is done save for a bit of fine tuning. You can pretty clearly see how the different parts will fit together at this point. There are a few different variations of this joint, but I like this one a lot with the stub tenon that protrudes below the dovtail portion. That little bit of material adds a lot of resistance against twisting.
From here I fine tuned the fit between the two halves, mainly by making adjustments with a chisel to the male end of the joint. Once the two halves fit together nice and snug, I dyed one half with sumi ink, and coated both with liquid glass finish.
Here are the parts going together:
And that’s it for this variation of the ari-tsugi joint. It’s not super complicated but you still need to be really careful with layout and cutout to ensure a good fit. I aim for no gaps except at one crucial point which is at the very end of the dovetail. Leaving a slight gap between the end of the dovetail and it’s mortise ensures that the dovetail shape can fully function to pull the shoulders nice and tight. Conversely if the end of the dovetail runs into the end of it’s mortise it will tend to push the shoulders apart (it’s the same principle as cutting a tenon so that it’s a bit shorter than the depth of the mortise to prevent the tenon from bottoming out before the shoulders fully close).
Beautiful work!