4 Leg Stool – Fabrication

Fabrication for the 4-leg stool started like most projects with some bandsawing and milling. The individual parts for each stool are pretty basic, just legs and stretchers, which made milling the stock pretty straightforward. For these stools the stock I chose was Japanese mountain cherry, yama-zakura (山桜), which is really similar to American black cherry in terms of grain density and texture, but the color is a touch lighter.

After milling I busted out a few ballpen marking gauges for laying out the mortises. It’s always handy to have a bunch of these so you can set one for each specific measurement.

And here’s a peek at the mortise layout on the legs. I went with double mortise and tenon joints for extra strength. The legs are 30 x 30 mm, so I could just sqeeze in a pair of mortises with a width of 6.4 mm, which is the size of the smallest hollow mortiser chisel I have.

Unfortunately I forgot to take photos when cutting the mortises… not that there was a whole lot to see. The biggest difference from normal mortising was that I made a 3 degree wedge/bed to set each leg on when mortising. My mortiser doesn’t have any tilting capability, so cutting angled mortises required making a wedged shape bed to support the stock. But aside from that, cutting the mortises was pretty straightforward, and went smoothly.

The trickier aspect to cutting the joinery was dealing with the tenons, which started with angled shoulder cuts. I decided to use the sliding table saw for cutting the shoulders, and made up a simple plywood jig with a couple fences and series of stops. Since the stool is wider than it is deep, and with the legs being splayed out, there are 4 different stretcher lengths to cut for each stool. The jig below in it’s current configuration only allows me to cut two different sets of stretchers, then I have to unscrew and reposition the stops to cut the other two sets. Next time I’ll proabably make a second jig so that I can accommodate all 4 sets of stretchers without having to move any stops.

The two fences with opposing angles allows for cutting of both sides of the stretcher’s angle shoulders. Cut the shoulder on one face, then flip the piece over and move it to the next fence for cutting the opposite shouler. The dangerous part about this setup is relying on two fences and stops for cutting opposing shoulders on one piece. There’s a lot of room for misalignements and little errors to creep in.

I inserted some countersunk screws into the end of each stop, giving me a little bit of fine tuning and adjustment ability, which really worked out well. Ultimately I’d like to rework this jig and make something a little nicer, but for this first small batch of stools this jig worked quite well.

For cutting the tenon shoulders I used a tablesaw fence jig with a screwed on plywood guide which allowed me to cut the tenons in a similar fashion to a tenon cutting tablesaw. Essentially the operation between the jig below and a true tenon cutting tablesaw are the same; both support the wood allowing you to plunge the workpiece into the blade for cutting the tenon. There is an adjustable stop on a tenon cutting tablesaw, but in this case, the surface of the tablesaw acts as the stop and the depth of cut is simply determined by raising and lowering the blade.

Short of having access to a tenon cutting tablesaw, I actually like this setup a lot. I find it to be faster and more accurate that tenon cutting jigs that you slide. For one all the parts are fixed, and the only thing that moves is the workpiece which you control. The overall sitation feel really rigid and safe to me. Also, not having to clamp the workpiece like you do with sliding tenon cutting jigs, saves a lot of time when you’re cutting a huge batch of tenons.

Here’s a quick video showing the jig in action:

When cutting the tenons I first cut the outside cheeks, then reset the fence/jig and cut the inner portion of tenon (forming the tenon thickness). Lastly I reset the fence/jig one more time to cut the narrow end of each tenon (tenon width).

One tricky aspect to using this tenon cutting jig is setting the depth of cut. Due to the radius of the blade you can’t fully cut the tenon cheek if you set the depth at or just shy of the shoulder. The illustration below shows an extra wide tenon which amplifies the issue.

In that kind of situation usually I would raise the blade such that the full face of the tenon is cut, which has the effect of also undercutting the tenon shoulder.

You can see what I mean if you look carefully at the shoulders of the tenons on these door parts from another project. There’s a light amount of undercutting on the shoulder around each tenon.

Given the small dimension of the stool parts I didn’t have much room for undercutting, and the angled shoulder cuts also complicated things.

One solution would be to angle the jig to bring the shoulder parallel with the tablesaw’s surface but doing so would only cover half the tenon, and then I’d have angle the jig in the opposite direction to take care of the opposite sides of the tenon. Essentially two separate setups.

Anyways, all that is to say that once again introducing angles into a piece of furniture (or architecture) really starts to complicate otherwise simple tasks.

For this first batch of stools I kept things somewhat simple and to ensure that I could cleanly cut the tenon cheeks on the outside faces I made all the shoulder cuts just a hair deep (into the tenon) to ensure that the outer tenon cheeks came out clean with no cleanup required.

Below you can see the slightly deep shoulder cuts which allowed me to cleanly cut the outer faces of the tenons. But I didn’t have that option when it came to clearing out the waste between the tenons. With the angled shoulder and inability to undercut I was left with a little bit of material to clean up by hand.

Here are the tenons after chiselling out the last bit of waste from between the tenons. Here you can more clearly see how I scored the shoulder cuts slightly deep in order to cleanly cut the tenon faces off the saw.

The last bit of work on the tenons was to chamfer the edges. I used a little kiwa-ganna to take care of the inside edges…

… and a small plane for chamfering the outer edges.

And here is a finished tenon after chamfering.

After a few hours mortising and tenoning, I ended up with a nice stack of parts with joinery complete. The joinery for these stools is really simple in design but tricky in execusion. It’d certainly be easier and likely faster to just use dominoes for these joints… but that’s no fun. I also don’t think dominoes would be nearly as strong, and ultimately I’m thinking long term for these stools.

Well that’s it for now. Kind of got lost in the weeds there talking about the tenon cutting jig but hopefully it illustrates some of the challenges of working with tenons with angled shoulders.

Stay tuned for the rest of the stool build soon. And thanks for reading.