Tuesday 16 November 2010

Tapered sliding dovetail bench

  A bench for Garden for George

Some projects just take years. I was approached 3 years ago about making a bench or benches for a garden in memory of George Harrison. The representative and I went through all my designs and finally, a couple of months ago, settled on a design that came from using tapered sliding dovetail joints in a bowl horse. I had never made such a bench, but was comfortable making the joints for green wood work tools. A great joint that can easily be knocked apart, and which gets tighter and firmer when pressure is applied.
Again it was a short lead time and great fun to make. Just before I confirmed that I would make the bench I had to make a pre-prototype-prototype, which is what I call this little stool.

I learnt a lot about this joint made from sawn and planed timber and it took me a long time to figure out how to mark out the legs. Marking out and cutting the mortice is simple, not so with the tenons on the leg, lots of compound angles that made my head hurt. If anyone knows how to figure out these angles mathematically so they can be transferred to the legs then please let me know.My solution is simple, and I suspect it is a way that many of us actually work things out. I made a mdf angle template, for each side of the joint.

 The dovetail joint has a slope of 1in 6 just like a normal dovetail.
After making the little stool, which I really like, even though it was made with the crappiest bits of wood in my shop. It has a solidity and presence that other stools I have made do not. It also has a price tag equal to its weight, not this one, but a similar one you will commission me to make you ; )

The plank for the bench was in the £300 mark - expensive - so I made a prototype from a 4 inch thick oak plank that had woodworm. I also wanted to get the angles of the legs and back right, before committing myself to the expensive plank of wood.

One problem with making the joints for the bench was that the plank of wood did not fit through my planer thicknesser, so it had to be hand planed. I also kept the dome in the top of the wood, to help shed water, but had to get rid of any wind. I did not have the proper planes, or time, to really square the timber off as I would have liked. So each joint was slightly different, I had to make lots of these templates.

The legs are hand-planed down, and had to have lots of fitting to ensure a tight and even fit. The waste was taken off on my band-saw, rather than using one of my ripsaws.
Click on image to embiggen

The bench is going outside in a public place so I also glued the legs in to help with keeping water and eventually rot out of the legs. Most of this bench is made with hand tools and no sandpaper.

It is a simple but elegant bench that takes quite a bit longer to make than its looks suggest.

oak bench, tapered sliding dovetail joints from Sean Hellman on Vimeo.
They also come flat packed, and simpler than Ikea furniture to assemble, that is if you can lift it!


  1. Hey Sean! That looks really well. Would a sliding bevel be of assistence when copying the angles to the tenon. How does the back top fasten on? Can't see any pegs.

  2. I really like the design of the bench. I wish I could help with a tip for making the legs... no tips. It does seem to me it would be easier to make the legs first, then cut the mortise to match... easier to measure and lay out I would think.

  3. Hi Sean,
    A friend of mine, Chris Amey made a sculpture using this type of sliding taper joint. I know he made up jigs but he might be able to help with the geometry

  4. Hi Sean,

    Love the idea of making a everyday bench in a different way and I can appreciate the messing about you had to do.

    Cheers Mark

  5. Bravissimo, Sean. Unsymmetrical mortise-and-tenon work. Very difficult stuff to do, and your solution beats mine. I would have cut cardboard templates port, starboard, top and bottom, and used them to mark out the tenon. Cut oversize and shave to final fit. Really have to think about it some more; it's s real challenge. Beautiful work.

  6. "Embiggen"? You learn something new everyday.

  7. Hi Sean,

    Great to see this joint getting used more round these parts! I first properly came across it when working in the French Alps – used to assemble matched doors in place of the ledges we tend to use over here (no need for nails or braces!). But in the Alps most of the timber is softwood (spruce/fir/larch), which is a little easier to whittle away than oak. I think they also might have had a lack of metal to make tonnes of nails with? I have another distant memory of seeing it used on the back of picture frame mitres – running across the mitres to joint them together. That was on some very special picture frames Peter Schade of the National Gallery showed me once.

    I can only guess how they would have shaped the long mortise (or housing) before the days of skillsaws (bearing in mind their doors in the Alps can be up to 1m wide). I personally, start with the tenons (or wedges) first, ripping them down with a skill saw set to the required tilt angle and following a chalk-line. Then I lay the tenon (large side down) over the area I want to create the mortise (on the second piece of wood) and transfer the four corner positions using a very sharp pencil and a ruler laid up the slope of the tenon. I then have to transfer these positions down the sides of the timber to be mortised. Now, I make a line along the sides showing the depth of the housing/mortise (a marking gauge helps!) and take a sliding bevel to then transfer the angle (which I had set my skillsaw tilt to) back up the sides from the four intersections to the top surface again. Finally, two pencil lines connect these four positions across the top surface and I simply skillsaw across the timber to the required depth along the two lines (up one – back down the other!); a few more kerf cuts in between the two allows the waist to be removed quickly and levelled off with a chisel and job done!

    I guess you could do exactly the same with a handsaw if that’s more your style. But I’d be quite nervous trying to cut all the housings (mortises) across the planks of a door and get them lined up perfect! But you could even them out with a pairing chisel after.

    It gets more complicated, of course, the more you skew the angle of the tenons across the surface of the mortised timber, because the sliding bevel can’t skew itself! But there are ways - you could make a test skew-cut through a scrap piece of timber and take the new compound angle from that.


    Chris Amey.

  8. I love this bench. Simple, clean, gorgeous!

    I agree with flying shavings, how does the back fasten on?

    Again.... gorgeous!

  9. Richard and Dave, I was going to be clever and dovetail the seat back rest onto the posts, like the rest of the joints, but one, ran out of time and two, realized that it would be an extremely complicated and time consuming way, if not impossible. The posts would have to slid into the bench seat as the back rest was being slid onto the top of the posts. So I cut a rebate into the post for the back rest to sit on and screwed and pegged from the back, I could have just pegged, if no metal was to be used.

    Tom and Chris, as you are Devon folk do give me a bell if you are passing my workshop, and pop in to say hi. Chris I have seen your work up at Heathercombe and liked your monolith sculptures of last year. Tom how is the chair making going?

    Swirt, I do find the lay out and cutting of the mortices first far easier. It is also easier to work on making the tenon smaller that it is to change the dimensions of the mortice.

    Thanks everyone for your input and kind comments, maybe one day I will find the way of working this out mathematically

  10. I want to re-do our patio benches and other outdoor furniture. This one is great! I like the personal touch of hand-done work instead of plastic boring run-of-the mill outdoor furniture. Thanks!

  11. great work Sean
    all the best chris nangle


Sorry, because of the huge amount of dubious people leaving spam comments for their useless stuff, I unfortunately have to bring back word verification.