Intro: Turning Green Wood Legs for a Stool
I'm planning to make my second three-legged back stool following the design in Chris Schwarz's brilliant book The Anarchist's Design Book (a follow-up to the Anarchist's Tool Chest), which is sold here. Chris details everything you need to know to design and make your own staked chair in this book, so I'm not going to repeat everything he discusses, but I did something a little different, which is to make my legs out of green maple, that I wanted to talk about. I will also make my spindles this way, but it is a similar procedure. In the book, Chris shapes the legs and spindles into tapered octagons and then turns tenons on the end. I acquired a log of maple and wanted to turn them on my spring pole lathe into tapered cylinders (i.e., cones), then dry them, then add the tenons. I'm still waiting for them to dry, but may post another instructable on the stool, if there is enough that I do that is different from Chris. Either way, I don't want to simply rehash what he's done.
Onto the turning!
Step 1: Splitting Logs
I acquired 2 eighteen inch logs of clean, fresh Michigan maple from a friend's dad. The first thing before I even had a clear project in mind, was to split them. I didn't photograph this stage, but here's the basic procedure:
The logs were maybe 8 inches in diameter, cut from the same tree. The friend's dad who gave them to me tried for the clearest pieces he could find. One had a couple knots, the other was darn near perfect. I used a froe to split them. On the imperfect piece I also had to use a wedge because it was slightly drier and had an embedded knot that kept it from splitting cleanly. The first piece split perfectly with just a few whacks from the maul.
Basically, to split a log, you lay the froe across a diameter and whack it with a club. The log wasn't perfectly fresh, so it had developed some radial splitting from drying out, so I choose my first split along one of the bigger cracks. I then split the halves into quarters. Two quarters I split into thirds for the spindles, and the other two in half to make eighths. The more difficult log I split twice. One entire half became a bowl, the other half I had to used a wedge to even split and it turned out to have a huge embedded knot, so now it will be firewood. If it had been greener, even with the knot, I might have been able to make a spoon from it, but it would have been hard to work with hand tools as dry as it was.
With the log split, I proceeded to split out the heartwood and pith by laying the froe along the radial rings, instead of across them, whacking the froe with a maul, then prying off the inner part of the wedge. I seal the ends with Titebond III glue to keep cracks from getting worse and slow down drying. For now I left the bark on. I'm not sure the best practice here, as I am new to green woodworking, but my theory was that I wanted the pieces to stay a little wetter until I could work them, so that's why I left the bark on for now.
Step 2: Paring the Wedges
Once I could get back into my shop, I picked my three best larger pieces to make into legs, then a bunch of smaller pieces that could be spindles, and a couple pieces to try to bend into a crest. I didn't have enough material to do the seat from these two logs, so I'll have to think of another method.
First thing is to peel the bark off the three leg pieces with a drawknife. Ideally, if I had a shavehorse, I would be able to use my drawknife to take these pieces to roughly cylindrical for final turning. Since I don't have one or space for one, I used my leg vice to hold them, then treated them more like a board, in that planed them square then octagonal, then turned them.
To do this, after removing the bark, I picked the flatest of the two wedge surfaces and planed it flat by hand using a piece of heartwood to prop up the wedge, and butting it against my bench dog. By the way, split maple reveals one of the prettiest wood surfaces you can imagine. Maple is full of ray fleck that you don't see when it is flat sawn. Really beautiful stuff.
With once surface flat, I used my draw knife to square the inside edge to that surface, then refined with a handplane. I needed a 1 5/8" square piece to start, so I used a gauge to mark that off those two surfaces, then used the drawknife to rough them in, finishing with my electric surface planer.
Once I had the blanks down to square, I planed them to octagonal. The device that allows you to do this is a v-block, a small scrap of wood with a right angle cut out of it. That's it. You lay the piece onto this, and butt the end up against a dog or stop and then plane (you'll be planing downhill) the edges down by eye until you are roughly octagonal. You can also make octagons from square cylinders using the method Chris Schwarz shows in his book (or that I'm sure you can find online).
Step 3: Turning
I have a simple plastic center marking device that I mark my centers with. I then use and awl to make a starter hole for my points. I use a spring pole lathe with 2 dead centers. The design is one from a Popular Woodworking issue not too long ago, in an article by Roy Underhill. It's the same one you see him using on some episodes of the Woodright's Shop.
My legs need to taper from 1 5/8" to 1 1/8". This leaves me plenty of material at the thin end to make a tenon on. The legs will dry to ovals, but that's not a concern at all, since I won't cut the tenon until the legs are dry. You want bone dry legs for any kind of chair. Otherwise, if the legs dry further they will shrink and become loose.
Chris calls for 24" legs, but my logs were only 18", so my stool will be much lower to the ground. I think it will be a good stool for sitting in the grass and maybe for camping or fishing.
My pieces all had some splitting, but only on one end, so I chose that end to be my tenon end, since I will need to wedge the legs anyway, and doing so will close up the splits.
The first leg I turned was the back leg, and I turned it thick. I was experimenting at that stage so it is the ugliest one. The other two I turned more to the exact dimensions. A thick back leg should work well anyway.
I set an outside caliper (I use an old Starret caliper I bought used from an online tool dealer for cheap) to 1 5/8", then used a parting tool to shave down to that diameter on one end. When the caliper slides over the piece, you're done. Then I set it to 1 1/8" for the other end. Then I picked a point roughly in the middle and set the caliper to 1 3/8" and made another mark. On the final leg, I did another part halfway between each end and the center, at 1/8" diameter intervals. This helped me get the taper just right.
Before digging in, you want to really set your centers. I load the piece without the cord, whack the moveable jaw in place, manually turn it, whack some more. Then I remove the piece, add a little beeswax to the holes, and remount it with the cord wrapped around the end. Then I re-set the lathe, turn without tools, give it a few more whacks, then try tools. I found this out the hard way when one of my centers drifted because it wasn't set well. At least for me, giving yourself plenty of extra bulk can help make up for these kinds of mistakes, but it also means you have more to cut away and more work.
That done, I used a big roughing gouge to get the octagon to a rough cylinder, then just start wasting away wood until I get to a tapered cylinder. I rarely got my centers perfect on the first try, but my octagonal blanks were big enough to account for that. If it's off slightly, I approach the piece lightly at first to knock down the high points, then dig in. I kind of learned as I went, but trying to work the tool at a skew so that you're catching it toward the outside is desirable. If you end up with a flat surface, just turn that part of the leg in so no one sees. A lot of classical turned pieces had flats. It doesn't really matter.
A few points:
- I used a straight edge to check that I was flat from parted point to parted point as I worked toward the taper.
- It wasn't important to me that the taper be perfect, but I wanted it to look as nice as I could get it and it was good practice with the tools
- Experiment around with angles of the gouge, fast turn versus powerful turn, and tool direction.
- I did the whole thing with just three tools.
- My method was to turn half the leg, flip it over, then turn the other half.
- As I'm turning I watch the area I'm cutting and work the taper in by eye, then go back and check my progress.
- A spring pole lathe is exercise. Take breaks and stay hydrated!
- Remember you can always remove material, but you can't put it back on!
- As a final step I like to smooth out the piece with my skewed chisel. This is a tricky tool to use. You want to angle it so that the tool makes contact on the part of the skew closest to you at an angle. With a little practice you can achieve a very smooth surface with just the skew chisel.
- I'm not that good at this yet, but it is a load of fun
- For the front legs, I decided to add a bead. I've seen Roy Underhill make beads with just a skew chisel. You cut into the piece with the tip, then use the heel to round into the groove. I had a pointed parting tool so tried with that, but it was tricky to get the angles, so I don't know if I recommend that. I had to finish with light cuts from the skew.
Notice that on one leg the heartwood invaded the piece quite a bit. The log had an uneven run of heartwood. I think it looks cool, and heartwood is almost as hard as sapwood, so I'm not too worried about it's structure. Plus, given how low this bench will be, I won't have far to fall if it breaks.
As a final note, these were my first pieces turned green. I've turned some dried wood before. Green is MUCH easier, but still my third leg was better than my first.
You can't really get a perfect final surface on green wood. So once it dries, I'll use scrapers to put the final surface on it, but I think it's easiest if you smooth it as much as possible now, because it will warp to an oval shape. However, it should stay perfectly straight along the axis, which is the most important thing. If it does bend, then the tree had a hidden defect and you were hosed before you even started. However, with splitting usually what you see is what you get. Warping, bending, and twisting tend to be artifacts of sawing wood, trying to force the tree into the shape you want, rather than letting the grain dictate what you do.
I hope to add another instructable on making my stool once these legs and the spindles I'll make dry out.