Folding Stool 2A Prototype
This walk-through was made while completing three of these stools for friends. I had hoped that doing them batch fashion would result in some efficiencies. That didn't seem to happen. Part of that might be due to my rather chopped up shop time and lack of excitement for making stools #5, #6 and #7.
That said, it doesn't take that long to make one, I just have a long list of things I'd like make and things that need to be done around the house. These took me 4-5 hours each. Finishing and final assembly was about half of that. It's really hard to put finish on an assembled stool. You really need to do it as you go. I'll cover that in more depth in the finishing section.
That total could be shortened considerably if you are less fussy than I am about your finished product. You could do a "munitions grade/basketman" level of stool in about 2 hours. But that's not how I make things, so follow along if you want a nice stool that will last a couple of hundred years if you're careful.
A note about measurements: pre-industrial furniture didn't follow carefully measured plans. there are parts that are important and those were laid out with care. Everything else was cut to fit. For this chair, the critical part is the layout of the holes for the folding mechanism. Other than that, there's room in almost every other measurement. If your legs turn out 24" instead of the specified 23½", it's fine, really.
Preparing the Stock
Your wood of choice is a clear hardwood. I recommend oak, it's cheap and more than strong enough. But feel free to use whatever you have to hand, this doesn't take a lot, about 4 board feet.
Everything is cut from ¾" thick stock and all parts are 1½" wide. You can either mill this down from 4/4 rough stock, or, if you're wealthy, you could buy 2S2 red oak from Home Depot or similar and rip it to width.
You'll need 31 linear feet of ¾" x 1½" stock cut like this:
- 8 Legs @ 23½"
- 4 Feet/Arms @ 15"
- 8 Seat boards @ 14"
My recommendation is to cut all your stock to width first, then cut things to length as you need them. It's important that all seat and leg parts be the same width if you want this to fold. Have a couple of extra pieces so when you mess something up, you have more of the same width already to hand.
The Folding Mechanism
Let's discuss the folding mechanism and how to layout the pivots before we get into making firewood. Math isn't my strong suit, much less geometry, so there are probably better ways to go about this, but this works for me. There are no doubt many different angles that make a sittable chair, but I am going to stick with 45 degrees for the very practical reason that it makes construction simple.
Take a look at the photo to the left (you might need to click into it and look at the full resolution version to see the measurements), the basis of the mechanism is a right triangle formed by the 2 seat pivots and the leg pivot. Bisecting that gives us the information we need to layout the pivot holes on the legs. Yes, I know the measurements are not exactly correct, but they are close enough for woodworking.
This makes a seat that's 14" wide. Fine for a stool, but narrow for long seating, at least for some of us. I scaled this up to ducal size for the Type 2B stool I built. That used 10" & 14" for the spacing, which yields a seat that is 20" wide.
Making the Legs
The legs take the most work, so we'll start there. Cut 8 pieces to 23½". The exact length doesn't matter, but for a good result, they should all be EXACTLY the same length. Or at least the exact same length between the shoulders of the tenons you are about to cut.
But before we do that, it's probably best to drill the pivot holes in the legs. A drill press is useful here, for the best results, you want these holes centered in the material (for strength) and straight (to keep the resulting chair from binding when you try to fold it).
The rule of thumb for M&T joinery is to make the tenons ⅓ the thickness of the stock. That's generally fine guidance, which would mean ¼" dowels for this ¾" stock. But I find those dowels to be a little flimsy, so I use 5/16" dowels for my pivot pins. And since I typically use oak, I am not worried about making the legs too weak with the larger holes.
YMMV, but check your dowel stock once you pick a size. I have found that dowels from the big box store tend to run a little undersized (or oval which means they weren't all that dry when formed). On the other hand, I have a bundle of dowels from a millwork vendor online and they are all slightly oversize.
If they are oversize, and you have a dowel plate, it's a simple matter to resize them. If they are undersized or, if you don't have a dowel plate, you'll need to pick an appropriate sized drill bit. I have a dowel plate, so I resize my dowels to 5/16" true. You are going to want a hole that's slightly oversize so things pivot easily. I use 11/32" for my 5/16".
Layout the holes as follows:
- one hole 2" from one end
- one hole 12" from the SAME end
You need to be careful here, it's easy to get confused and drill the second hole from the wrong end. Believe me, I've done it. The functioning of the fold depends on these holes lining up through 8 boards. So you need to either be precise or so sloppy it doesn't matter. I prefer a tidy, precise job personally so I used a drill press, fence, and a stop block to make consistent holes.
OK, with the holes sorted, it's time to move on to cutting the tenons on the ends of the leg boards.
Going back to good practice for M&T joints, we're going to make the tenons ⅜" x ¾" and ¾" long. Again, if you want this to look nice, the distance between the shoulders on all the legs need to be exactly the same. There are tons of articles and videos out there covering this joint so I won't go into here. Just want to say, neatness counts.
Making the Arms/Feet
Here's that opportunity to make some firewood you've been waiting for. The arms and legs are basically two sets of mirrored components. The easiest way to lay them out that I have found is to make one leg frame completely and then the matching frame. I'll explain it below.
Start by making 4 identical boards. They must be long enough to accommodate all 8 legs but they can be as much longer as you like. I used 15" long as shown here. The shapes and decorations for these pieces vary quite a bit. We are going to keep it simple for this basic stool and whack off the top corners at 45°. Do this now, while it's a minor thing, it will help you keep the parts straight.
We will layout the mortise locations now, so take two of those, lay them side by side with the clipped corners on the same side (the right, for instance). The arms have the mortises on the bottoms (sides without the clipped corners), the feet have them in the top (sides with the clipped corners). See? Handy already.
For the whole layout, you need only two measurements. One is the offset on the "near" side and the other is the center to center distance between legs. Take a look at the photo to the right where I demonstrate this with two pairs of dividers. One is set to the offset from the near edge and this can be anything really, it's just the overhang.
The other one is very important as it's the spacing between the legs. There are a couple of ways to do this. I use the centerline, but you could use the edge. The gap between the legs needs to accommodate the opposing leg plus some amount of slack. How much you want is a judgment call. It's in my nature to try and make things as tight as possible, so I butted the leg boards against each other to set the dividers. I did that the first time and one of the legs ended up a little bit off in their lane and that was a pain in the ass to sort out. I suggest an ⅛" slop, minimum. That way if one board happens to be slightly thicker than the others, you won't have a "problem".
The period illustrations show stools with a variety of fitting. Most are seemingly pretty tight, but there are a couple that is so loosely goosely I would not attempt to sit in them myself. I guess what I am trying to get across is that, like the whole project, don't be hung up on specific measurements. Work to making things fit and function properly.
OK, with the dividers set, walk off the location of the 4 mortises on the arm. You should end up with what seems like an awkward amount of board left at the end. This should be the width of the opposing leg plus the amount of overhang you started with. If it's longer, trim it, if it's shorter, get another board and try again :).
With the spacing marked out, chisel out your mortises on all four pieces.
Now the fun begins. Fit the leg tenons to the mortises you just cut. At this point, it's usual that mark parts as you fit them so you can reassemble them later. If you didn't already know this, no matter how hard you try, hand-cut joints are not completely interchangeable. Accept it, embrace it, and mark all your parts once you start your joinery.
When you're done, you have two leg assemblies that have tightly fitted joinery and are spaced such that interlace nicely as shown on the left.
Making the Seat
The seat boards are the simplest of the parts. All 8 boards are identical. Start at 15" long, they get trimmed to fit, it's really around 14¾" I think, The seat boards get the other two holes. And, like with the legs, care and precision pay off.
The first hole is ⅞" from one end, the second hole is 7⅞" from the SAME end. It's not quite symmetric, so, again, care pays off. Layout and drill all the holes.
You have to bevel one end to 45° to lay on the legs, but the "back" end, at the pivot, doesn't need to be beveled. I do it anyway because it looks better. In the period illustrations, some were and some were not, so it's up to you.
Assuming you are going to do it right, chop off that pivot end at 45 deg. I cut them just far enough to get a full bevel. You don't want to weaken the pivot area too much.
The other end, I would leave ⅛" to a ¼" long for now. When we assemble the stool, we'll trim it so it's a perfect fit. Don't assume you can nail it, maybe you can, I can't. But then I want the seat real flat. You can be a little off and it's fine, just a little lumpy.
I use a Boiled Linseed Oil blend (see all about that Using BLO). You really want to do most of the finishing before you assemble the stool. Once it's together, it's really hard to get the finish in all the places you want. So, tape off the mortises and tenons to keep the oil from fowling the glue surfaces and go to town.
I go with 3 coats on something like this. On stuff I love, the more the merrier. If it starts to look dry or dusty, recoat. This isn't the type of finish that lasts forever. But it's dead simple to renew. Just wipe more on.
With the finishing process is done, or you're bored with it, it's time to assemble the stool. If you failed to keep the oil off the tenons, it's time to clean them off with a solvent like mineral spirits or acetone.
For this step, it's useful to have an extra set of hands, it's a little awkward to clamp it all up. There's probably a better way, but I don't know it. Like with all assembly steps, size your clamps and lay them close to where you will need them. Have glue, glue solvent, and tools handy to deal with runs and whatnot.
Apply glue and assemble one leg set, then set it up on its side and clamp it up. Now assemble the other leg through the first and clamp it up as well. It will look something like what I show here on the left.
When the glue is dried and the clamps have been removed, you can put the leg center pivot dowel into place.
A Tip: I lightly sand the dowels so they are smooth and run them on a block of paraffin I have handy for plane soles. These steps make sliding the pivots in a whole lot easier. I also stick one end into the pencil sharpener and knock the corner down, basically bevel the first ¼". This helps with locating the holes as you go, you'll cut that part off later.
Now you can use an F-clamp to stand the stool up as shown in the test fit photo above.
Now you can start working on the seat. They should be close to the correct length already, but you may have to trim them a little. Put in a couple, and observe how they are laying. Trim to fit so the seat boards are co-planar and the center pivot hole lines up. You adjust that by tightening or loosening the F-clamp.
Once the seat is completely in place, you have a stool! Test fold it a few times and work out any kinks.
The last task is to trim the pivot dowels to length and affix something to the ends to keep them from falling out or the outside seat boards from falling off. I tried a couple of things, none of which were completely satisfying. The first one was making a pyramidal shaped piece with a hole drilled in it. This looked OK but was a complete pain to manufacture. Remember, you need 8 per stool. Then I tried two different sizes of commercially made dowel ends, small finials really. The problem with those was the predrilled hole was too small and holding one of those well enough to redrill them without marring them is hard. I have seen a metal rod used for a pivot with the end peened over on a burr. That's fine, but not attractive and I don't like mixing metal and wood in that way.
Another solution I have seen it to use blind holes on the outer parts. You drill them only 3/4 of the way through and they contain the ends themselves. This is a nice and tidy solution, but not one supported by any illustrations I have found so far.