Sage-Kama Desk – Build 2

On to the next phase of this desk build. In this post I thought I’d share how I cut the okuri-yose-ari, or the segmented sliding dovetails, that join the cross pieces (aprons) to the desktop. As I mentioned in a previous post the beauty of these joints is that they allow you to utilize the strength of a sliding dovetail joint without having to cut a groove through the side of the table top. That was one consideration of mine in choosing to use this joint for this desk, and the other was, well, simply to give this joint a try. This was my first time using and cutting out this joint. I’d probably do a few things differently next time but all in all things went well.

I took some video during cutout, which you can see below. Hopefully the process is fairly clear. I did try to record some narration over the video, but man am I bad at that. So I kept things simple with the video, and I’ve got some more photos and more thorough details on cutting this joint below.

First step, I whipped out a really simple jig to guide my router for cutting some slots.

I made a light cut into the end of the jig to use a reference point for locating the jig relative to my layout marks. I repositioned the jig 4 times for each joint, so having reliable reference point is key.

Then I proceeded to cut a slot at each joint location using a straight router bit. Routing these slots is simply a way of removing material to make the cutout easier for the next step, which is to open up these slots with dovetail bit.

And here is one joint after running through with a dovetail bit in my trimmer router.

With the dovetail slots cut, I put a straight bit back in my router again, and reset the jig for cutting the segmented part of this joint.

Here is one side of the joint after notching. The length of each segment is about 30 mm long.

And here is the finished joint after resetting the jig and cutting the opposite side of the joint. This was the first of the 4 joints that I cut, and I made a bit of a mistake. The lines running along the sides of the joint represent the outside face of the joining piece (the actual outside face of the cross piece). When I cut the first series of notches (previous 2 pictures) I set the jig and cut right along this line, mistaking it for a cut reference, and forgetting that it was telling me where the outside face of the cross member was supposed to land. So long story short, when assembled you can see a hint of the notches on this particular joint, and just on one side of it. Not the end of the world when all is said and done, but kind of a bummer none the less. If I was making this desk for a customer I’d be a bit more concerned, but since this is a prototype desk of sorts, that my wife and I will use, I just forged ahead.

Here’s another joint for one of the intermediate cross pieces after cutting and notching.

At this point the only work remaining on the female half of the joints was to square out the corners at each end with a chisel. So after some paring and chopping to square up the corners, I moved on to cutting the segmented dovetails on the cross pieces themselves. Unfortunately I forgot to take pictures during that part of the process, but you can see my approach in the video above.

To quickly go over the process, I first cut a dovetail down the length of each side of the cross piece at the router table, and I intentionally left them a hair fat to give myself some room for fine tuning later on. After cutting the dovetail I mocked up a set of blocking to hold and support the cross piece for notching with my trimmer router and an edge guide. The spacing of the notches was taken off the layout marks for the female half of each joint. Then it was a pretty straightforward process of simply setting up the router for the right depth of cut and edge guide setting, followed by careful routing of the notched segments.

Below is a test piece that I cut for dialing in my router settings. On the left you can see where the router bit was set too deep and I cut into the shoulder of the piece a bit. In the other direction the depth of cut is pretty shallow. Using the edge guide on my router, I set the cut such that each notch just barely extends below the depth of the dovetail at its base and narrowest point. In a previous post I showed how there are different variations of this joint, and sometimes the material between the dovetails is completely removed. Here I wanted to preserve the strength of the cross pieces as much as possible, since they are relatively thin in thickness, so I notched the dovetails as minimally as possible.

Another subtle thing you can see in the image of the above test piece is a bit of burnishing on the dovetail segments from test fitting the joint. After cutting the notches, I went back to my router table setup with the dovetail bit and started to take off a hair more material from the dovetails, just until I could start to fit the joint with a few taps from a hammer. Making really incremental, light cuts, at the router table allowed me to dial in the fit of the dovetails until it felt like the right fit. I like to cut dovetails like this just slightly on the tight side. How tight is really relative to the size of the dovetails, type of wood, etc. But in this case it felt right when I could advance the joint with a few firm taps from a dead blow mallet. In hindsight though, I would definitely make these a bit less tight in the future. The test piece here only contains three dovetail segments, but each cross piece has more than 3 times that, meaning the amount of resistance was way higher on the finished cross pieces. And when I actually did the final assembly of the desk, tapping the cross pieces into place was a TON of work.

Here’s one of the cross pieces with the joinery completed on both halves of the joint.

Ande here are all 4 cross pieces in place. The aren’t tapped in at this point, rather they are simply inset to test that the notches are all properly cut, allowing the segmented dovetails to be inset into the surface. At this point I could also give a few light taps to each cross piece to double check that the dovetails were engaging and pulling the shoulders of the cross pieces tight to the desktop.

Next week I’ll post some photos from handplaning and final assembly. Thanks for reading.