Jigs and techniques

Jigs and techniques

As with tools I’m trying to keep jigs simple and few. But this is chair making so they’re unavoidable.

Jigs and forms are used for bending, aligning and holding pieces of timber. Given that chairs are fairly complex shapes with lots of curves the jigs chair makers use get pretty specialised and this can put off the novice.

Leg bends seem to attract the most complex jigs. Have a look at Jeff Lefkowitz’s jig-as-artwork for the double curves in Boggs chairs. Wonderful. But if we’re building country ladder backs or Arts and Crafts chairs we only need one simple bend and we can get that with a block and a few clamps. Not much of a barrier to entry.

Curved on three faces this simple block acts as the bending form with the legs clamped to the bench and then later as the drying form with the legs tied across it. Here I’m lining it all up before steaming.

The back slat forms are more involved. I have used the traditional ladder style for these but I don’t really like them. If you don’t prebend the pieces they produce more of a kink than a curve and are better employed as drying forms after the slats have been mostly set in a more supportive form.

This jig will do double duty to hold the slat when carving the shape into it and so is worth spending some time on. If you want to cut down on the work you can just build the convex side and clamp the pieces to it but I have found that the sandwich method is better all round.

If you really want to cut down on jig building you can clamp the ends of the slats to the bench over the block but it won’t give you much control of the curve and ties up bench space.

Drilling holes in legs also seems to attract a lot of complexity. There are all kinds of shop-made devices for marking a centre line and drilling a hole. Mirrors, spirit level jigs and lasers all come out to solve the problem: how do you drill at a correct and consistent angle?

This is the simplest method I can find. I put a leg on the two joiner’s saddles I used for planing and scraping earlier and clamp them down. Then I mark the centreline by the extremely complicated method of using a right angle block of wood with some pencil graphite on it. This leaves me with a neat line along the length of the leg. Given that my bench top is flat I can then use this as a reference surface to judge whether I’m drilling straight. A square on the bench takes care of the angle.


The second set of holes in each leg must be at a specific angle to the first. Loosen the clamps or holdfasts, insert a dowel or stretcher, slide up a parallel sided block with a bevel gauge on it, clamp it all back down. Mark the centreline and drill. Harder to explain than to do!

Just the bevel gauge. The chair is made in England.

It’s not really a jig but the chair stick is worth mentioning. I build mine rather robustly from the same section stock as the legs. This means that when I lay a leg next to the stick flat on the bench I can put a square across both to mark all of the joinery.

Not essential – you might not think it’s worth making for your first chair – but it’s definitely worth it if you plan to build more.

Akin to the chair stick is the bevel board. I put all of the angles needed for each chair on it. Given that the geometry of chairs is fairly well established you might never need to make more than one.

Not for this chair! This is for a bench I built last year but you get the idea – mark the angles on a piece of wood and then you can quickly reset or check your bevel gauge.

Compass planes

Compass planes

I’ve been testing curves for back slats recently. That’s meant a lot of time with my compass plane making bending forms. That plane is a chatterbox. It’s in its nature. There are so many light, movable parts only partially attached to each other that it’s a wonder the thing can stay quiet at all.

Roughing in the curve with spokeshaves

Most plane makers go to great lengths to make their tools out of heavy, solid lumps of stuff. It keeps the chatter to a minimum. Compass planes are not built the same way.

The handles on my straight spokeshave show a lot more wear than on the round-bottomed tool. You can get quite a lot of curve before you need the curved sole.
Cambered iron

But there are things you can do. Starting with low expectations helps!

I used to think of my Record 020 as a jack plane. I expected it to do a lot of work quite quickly and give me a decent result. These days I see it more like a jointer plane. I use it for the last few shavings to get the final shape. The curve comes from a bandsaw, jigsaw or bowsaw followed by spokeshaves. They are my jack planes for curves.

As with all edge tools start with the sharpest iron you can hone. It won’t solve everything but at least you’ll know that’s not one of the issues. Grind and hone it like a jointer plane iron – with a small camber. Rather than trying to take a full width shaving I work the high spots and check for square frequently. I don’t expect to get beautiful long ribbons from end to end. Given that we’re making a curve the grain direction will change at some point and these things don’t go up hill!

The mouth and bed aren’t flush. Not ideal but it works.

If you’ve got a sharp, cambered iron, lightly set, you’re cutting downhill and you’re still getting chatter there are a couple of things worth investigating. The mouth of the plane is a magnet for resin. It builds up and needs to be scraped out. There’s little you can do about the step between the mouth and the frog. The frog has no fore and aft adjustment. I’ve tried shimming it with mylar and sheets of tin foil. Not worth the effort. Make sure that the cap iron fits well and the lever cap is tight.

With the mouth clean have a look at the peened pins that hold the frog to the sole. With the sole set for a concave curve these can stick out and catch. You won’t notice it when planing but it can’t help the chatter. You can sand the sole much as you might lap a smoothing plane. I didn’t notice a lot of difference but it can’t hurt.

And finally, with the plane perfectly set up a squiggle of wax on that rather rough sole makes the world of difference.

Not the most satisfying shavings but it’s the curve we’re interested in
Round and round…

Round and round…

On a chair leg’s journey from square to round (for the pedants: from cuboidal to cylindrical) there are several options for marking it out to get to octagonal. I’m a big fan of the spar gauge; they’re handy for any piece that tapers along its length. But for building the occasional chair a dedicated tool may be a bit much.

Here’s another way – one that I use a lot even though I have a couple of spar gauges in a draw.

  • Plane the future chair leg square to a hair shy of the final diameter.
  • On one the end of the workpiece mark the centre using the 45 degree fence on your combination square.  
  • Draw a circle (or just a quarter of a circle) with a pair of compasses.
  • Mark a tangent using your combination square.
  • Set your marking gauge to the point where the tangent meets the edge.
  • Use this setting to mark the length of the workpiece.
  • Set the leg in joiner’s saddles and plane until the marks just disappear
  • Draw a line on all eight sides.
  • Plane a few strokes until your piece is an even 16 sides. No need to gauge anything here – trust your eye and the length of the ever decreasing pencil lines.
  • Scrape with a concave scraper.
  • Sand in a saddle
  • Repeat until fade…

Or you could use a lathe.

Repeat until fade…