Maruta Bench – Build 1

A few months back I designed a bench as part of my goal for this year to produce a new furniture design every week. The first iteration of the design used square stock for the long seat rails, but all the other parts were round.

Overall I liked the form with angled legs and the diagonal braces for support. I also liked the look of the legs being round, as well as the leg stretchers and braces. But something felt a bit weird with the look of the square long rails. So I took another look at the design, this time making those long rails round too.

At this point all the parts are round. I can’t really explain why, but round forms seem to be in my mind a lot lately as I design things. I really like the softness they add to a design. In this case I particularly like the look of the Danish cord wrapping around the round seat stretchers. I also like how the joinery between round pieces of wood is evocative of joinery you often see on tea houses or small gates here in Japan. There’s something really beautiful about this kind of joinery where skinny logs criss-cross and join one-another.

After writing a bit about furniture design a few weeks back, the topic of repairability came up in one of the comments, and separately in conversation with a friend around the same time. Which got me thinking about building the bench with joinery that could be taken apart for the sake of repair. The woven seat is a no-brainer, and easily repairable, but I hadn’t really given a ton of thought to making the joinery itself demountable until that time. Who knows when your dog will get bored and decide that the leg of this bench looks like a good candidate for a chew toy. So I decided to make the bench joinery demountable by using pegs (komisen) to secure the mortise and tenon joints.

Pegged joinery is great for it’s reversibility, and it’s also a lot less stressful to assemble compared to glue-ups which involve a fair amount of stress to haul-ass before the glue dries. It does involve a bit more work to layout, cut and fit the pegs/peg mortises, but the extra effort isn’t that strenuous. And considering the life of the piece and how much longer it could be around if it was made to be repairable, then a bit more work to accommodate the pegs was an easy decision.

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So with the design and joinery decided, this past week I started building the bench, using Japanese ash (tamo タモ). The parts are relatively thick, with the long seat rails at 60 mm (about 2 3/8″) and the legs at 45 mm (about 1 3/4″). Unfortunately I couldn’t get material thick enough to cut the parts out of solid stock, so I ended up gluing up the legs and long and short seat rails.

With the parts glued up, I milled them to rough size on the jointer and planer, and from there began laying out the joinery. Below you can see the joinery layout on the long seat rails which are 60mm thick. On the left side is the layout for the mortise where the short seat rail will join. I also drew the diameter (56mm) of the short seat rail centered on it’s mortise for the sake of visualizing the relationship and size of the parts relative to one another. On the right is the layout for the legs which attach to the long seat rails with a 16° splay. The layout also includes mortises for the pegs (komisen in Japanese) which will secure the mortise and tenon joints. Typically pegs are oriented square to a tenon/mortise, but these are all angle diagonally at 45° (more on the reasoning behind that later).

In the image above you can see the size difference between the width of the 60mm long rails and the circle representing the short rail leaves only 2 mm remaining on each side. So the question becomes how to deal with this kind of connection. If I just drilled a massive hole at 56mm to inset the short stretcher, the remaining material on the outside faces of the joining piece would be pretty weak, especially once those pieces also become round. In this kind of situation the only real option is to scribe the tenon shoulders to match it’s mate (exactly as pictured above in the example images of tea house and gate roof joinery).

The legs and legs stretchers on the other hand have larger differences between the finished diameter of each part. I could have fit these parts by scribing too, but scribing is tedious and takes time, and I was curious to see how an alternative approach would work out.

So with that in mind I laid out the joinery on the legs a bit differently. Below are the legs with mortises laid out for the leg stretchers. The numbers listed are depth measurements. Here the stretchers are a fair amount smaller than the legs themselves so I decided I’d drill a hole to inset the whole shoulder into the legs. Stay with me, this will all make sense in time with more pictures.

Here are the short stretchers for the seat frame. You can see the round layout lines – a 60 mm Ø circle to match the final diameter of the long rails which these stretchers will join to. These are going to be scribed.

So layout complete, the first task was to cut the mortises. I started with the komisen. It’s good to cut the peg mortises before the larger tenon mortises. If you do this process in reverse order you tend to get blow out in the tenon mortises when cutting the pegs, which requires the added annoyance of have to use some kind of dummy tenon to prevent that situation. So komisen first, then tenon mortises.

These are the 6mm komisen mortises for the leg and leg stretcher joinery. The other bench parts were larger in size so I used 9 mm komisen for those.

Once the komisen mortises were cut I moved on to cutting the larger tenon mortises. Here is my setup for cutting the 16° angled mortises to accommodate the legs. Once again I’m using this cheap Hitachi drill/mortiser. Definitely not my favorite machine to use, but somewhat impressively, it gets the job done.

Here you can see the long seat stretchers with mortises complete.

From there it was time to start turning these parts round. The long seat stretchers are 1200 mm long (~48″), too long to fit on the lathe, so I shaped them using a combination of power and hand planes.

I’ve said it before and I’ll say it again, there’s something really satisfying about making rounds.

Next up it was time to start cutting the tenons on the short stretchers which join the two logs (long seat stretchers) that I just made. I took another experimental approach to making these pieces. I knew that scribing these pieces once they became round would be a complicated task. So I took a bit of a gambit on precutting the shape of the tenon shoulders, in the hope that I could then turn these pieces round on the lathe and have minimal scribing to do. Below you can see I’ve cut the tenon shoulders on the band saw within 1mm or so of my lay out lines.

Here’s another look at the tenons and rough cut shoulders.

And here’s a test fit of one joint. At this point the fit was pretty close, which was sweet. I love working with hand tools, but with 8 of these joints to cut in total it was nice to be able to get things as close as possible before pulling out my chisels.

One more step before turning these round was to drill a couple holes where the short diagonal braces will joint. The diagonal braces are simply inset into these holes with no tenons. I figured the braces will more or less be captured between the short seat rails and leg stretchers, and so they really don’t need any kind of special joinery aside from simply being plugged into a couple of holes.

Then it was on to the lathe. I was really unsure how this was going to work out, and I was expecting that the wood around the curved ends would blow out while shaving these pieces on the lathe. But it turned out to be no problem. With a sharp gouge, and gentle touch, these pieces came out really clean with no torn grain.

There’s lots more to share but this post has gotten pretty long, so I’ll wrap things up for now. But here’s a tantalizing look at one of these joints going together after a bit of scribing. I’ll cover the details of scribing next week. Thanks for reading.

https://youtu.be/Y249Vm_ogGw