Words and process photos: Peter Young
Studio photography: Andrew Porphyri
Stools in various forms have been around for centuries and not a lot has changed in the way in which these furniture items are made. Essentially there are two types of stool, those which have a seat attached to a frame, and those in which the seat is penetrated by the legs with the seat forming an integral part of the structure. It is the latter type we’ll focus on here.
1. Splay angle (left) – the leg angle as viewed from the front. 2. Rake angle – the leg angle as viewed from the side.
Splay and rake
While chairs may have vertical legs, stool legs almost always have splay angle as you look at the chair from the front (photo 1) and rake or side view angle (photo 2).
3. Variations in rake and splay angles can make a big difference even in a very similar design. The cedar stool in the centre has the biggest splay and rake angles of these three stools, while the walnut stool on the right has the smallest angles. The blackwood stool on the left has leg angles between the other two.
Variations in rake and splay angles can change the appearance of a stool even with a similar overall design (photo 3).
Many people are put off by the idea of making a stool because they don’t know how to make the seat mortises to provide the desired rake and splay angles. There is also the business of fitting stretchers to angled legs. There are some complicated methods involving mirrors and sets of sliding bevels and augers and while these methods work, there is an easier way involving a drill press and an angle jig.
Stools have angled legs for a number of reasons. The footprint of a stool is generally smaller than a chair; stools are generally taller than chairs; and many stools can be sat on in a number of different ways. All these factors add to instability, so angling the legs makes a lot of sense.
There are no absolute correct numbers for rake and splay angles but somewhere between 5 and 10° will look about right, depending on the design. If the legs are too far splayed, the stool will look like an ungainly newborn foal, and the ends of the legs will extend a long way beyond the seat margins, which might cause people to trip. For a circular or square seat, the rake and splay angles can be the same, but for a rectangular seat the splay angle is usually greater than the rake angle.
To accurately drill the seat mortises, we need to find the included or resultant angle. If you have a stool at hand, you can determine the resultant angle by placing the stool upside down on a table or bench and moving it around until one of the legs appears to be vertical. That is, it has neither rake nor splay. If you now place a sliding bevel against the inside of the leg at that point, this will give you the resultant angle. Furthermore if you draw a line from the leg across the bottom of the seat, this is the sight line or the horizontal line along which the leg appears to be vertical. In a rectangular seat, if the sight line is at 45°, then the splay and rake angles will be identical.
4. Open angled sled showing 8° wedge.
Angled drilling sled
The resultant angle and the sight line are all you need to get a consistent result. The next thing to do is to make an angled sled or drilling platform for the drill press.
5. Angled sled closed, sacrificial ply is screwed to the surface.
I do this by hinging two pieces of ply and angling one face with wedges (photos 4, 5).
The angle of the wedge is the same angle as the resultant angle. Strictly speaking, you don’t really need to know what the actual resultant angle number is. Using the sliding bevel, you can make some wedges for the angled drill press sled. However it’s better if you can use a digital protractor with a magnet to attach to the blade of the sliding bevel and you can then easily check that the angle on the sled is correct.
6. Template for drilling leg mortises, sight lines are drawn in red.
I like to make a template which is the same size as the seat, showing the location of the mortises and the sight lines (photo 6). I can transfer this information to the bottom of the oversize seat blank.
7. Templates for seat shape.
For shaping the seat, which is done after the mortises are cut, I use separate templates (photo 7).
8. Drilling the last leg mortise using the angled sled on the drill press table.
To make the leg mortises use a Forstner bit in a drill press. The seat is placed bottom side up on the angled platform with the sight line in line with the post of the drill press and the seat angled down towards you (photo 8). Now it is simply a matter of drilling each seat mortise in turn, following the same procedure with each. The mortise could be anywhere between 15 and 30mm diameter.
In traditional Windsor chair seats, a tapered mortise is used with a corresponding tapered tenon. The idea is that the taper provides a wedging action and the tenon is more securely locked into position than with a straight mortise. This method has worked well over many years, the only downside being that over time the tenon often comes through the seat a bit more than when the chair was made, which can cause some discomfort to the sitter.
If you want to use a tapered mortise and tenon you can use the method described here to drill a pilot hole and then use the appropriate angled auger to make the tapered mortise.
Making the tenons
I make the round tenons on the lathe as I find this is a quick and easy method. However you do need a lathe with a relatively long bed as the legs can be 600–650mm long. I leave a small 5mm shoulder which will contact the bottom side of the seat when the leg is fully home (photo 14).
Another method is to use a plug cutter in a floor standing drill press. It takes a bit of time and care to set up, but once that is done the work goes quickly. The drill press table needs to be accurately set vertically and the leg needs to be held securely so the tenon is cut in the middle of the leg. After making the tenon, create a shoulder using either a tablesaw or a handsaw.
Fitting the stretchers
You can now fit the legs to the seat 9 and check the angles. The next step is to fit the stretchers. These elements provide a lot of stability and are necessary except for the stools with really short legs.
The function of the stretchers is to push the legs apart and provide a really strong triangulation. In addition they serve as a useful foot rest. There are a number of different arrangements for stretchers but I commonly use one between the front legs, another between the back legs and then a central stretcher between those two.
9. To measure the shoulder to shoulder length of the front and rear stretchers, use battens as spreaders at the toe of the
legs to spread them evenly, then clamp a batten horizontal to the floor where the stretcher will go and measure between the legs at this point. Use blue tape on the inside of the legs and mark across from the batten.
I use spacers at the foot of the legs to push the legs apart and then clamp a batten across the legs where the stretcher will go, usually 130–180mm from the floor (photo 9). Use blue tape on the inside of the legs and mark across from the batten for the location of the leg mortise.
You can now measure between the legs and this provides the length of the stretcher from shoulder to shoulder. Getting an accurate measurement between two round legs can be tricky so I use two small battens taped together as you might for checking squareness for a drawer. Another handy device is a telescopic aerial from an old radio.
The stretcher shoulders do not have to be large, just 2–3mm, but they perform a really important function of pushing the legs apart. Only the top part of the shoulder will come in contact with the leg, but that is sufficient to do the job. The strongest option is to use wedged through tenons but stub tenons also work quite well.
10. Use a sliding bevel to measure the actual splay angle.
11. Use a digital protractor to record this angle.
12. For turned legs make a cradle by cutting a V into thick scrap stock and then use a wedge or a thick batten to raise the cradle to the correct angle. For all four legs, the top of the leg is to the left and the toe to the right.
To drill the angled mortises in the legs, you need to measure the splay angle on the inside of the legs (photos 10, 11) and then use this measurement to create an angled ramp for the drill press (photo 12).
For turned legs, I cut a V-shape in thick stock to hold the leg, but for square or rectangular legs a flat platform is all that is necessary. Either use a wedge or a batten under the ramp to obtain the correct angle, easily checked using a digital gauge (photo 12).
For turned legs, centre the Forstner bit on the bottom of the V of the cradle and this will centre the mortise in the leg. For stub mortises you can drill about two-thirds of the thickness of the leg.
For through mortises in turned legs you need to take some care to avoid break-out as the V-cradle does not provide support. I continue drilling until the point of the Forstner bit just comes through, then I reverse the cradle (top of the leg is now on the right and the toe is on the left) and drill through from the other side.
The stretcher tenons are made either on the lathe or with a plug cutter, as for the legs. You can now fit the stretchers to the legs and then the legs to the seat. You will immediately notice how the stretchers provide some rigidity to the whole structure.
13. To cut the stretcher mortises, use the V-cradle flat on the drill press.
The next step is to measure for the central stretcher. As for the front and rear stretchers, place spacers at the toe of the legs and then measure between the front and rear stretchers to provide the distance between shoulders of the central stretcher. Drilling the stretcher mortises is fairly straightforward as there are no angles involved. For turned stretchers use the V-cradle flat on the drill press table and an 8 or 10mm Forstner bit (photo 13). The tenons can either be stub or through wedged.
14. Shape the seat to provide a small dish for comfort and curve the edges.
Now put together the leg-stretcher assembly and then tap the legs into the seat mortises. Even without glue you will now have a very rigid structure, quite strong enough to sit on. Mark the tops of the legs where the wedges will go, they need to
be at right angles to the seat grain direction. If you have used through tenons on the stretchers you can also mark where those wedges will go.
All that remains to be done is to shape the seat. I like to have a small dish in the seat and a small curve on the long side and the short sides (photo 14). Use a bandsaw to rough out these shapes, then refine with a spokeshave and block plane.
Before glue-up I like to apply a coat of finish to all components. This really simplifies the removal of excess glue which can be just wiped off with a paper towel or dry rag, followed by a damp cloth.
The glue up is fairly easy. The leg- stretcher assembly is glued up first and then the four legs are tapped into the seat mortises. When the glue is set, remove the excess tenon wedge and plane flush with a block plane. Apply a final coat of finish and the job is done.
Peter Young is a studio furniture designer and maker who lives in Brisbane. He is a regular contributor to Australian Wood Review magazine. In issue 102 his article Variations on a Side Table shows how a popular design can successfully be varied in a multitude of ways.