Medieval woodworking part 5: pole lathe

Medieval woodworking part 5: pole lathe

No demonstration of medieval woodworking would be complete without a pole lathe.

I have spent quite a lot of hours this summer building an adapted version of Roy Underhill’s double spring pole lathe. It’s by no means medieval but it demonstrates the concept. And it doesn’t require a 20′ long sapling.

Yesterday was the culmination of the work I have been doing. I spent several happy hours demonstrating joinery and pole lathe turning at Fen Ditton 800. It was an exceptionally successful, well-organised and enjoyable event and I was delighted by the reception my little stand got.

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While I was setting up a gentleman in his seventies arrived and started asking a lot of very astute questions. It became clear that he had been a joiner for most of his working life and he was delighted to see someone working with hand tools. We spent about fifteen minutes talking about his career, the huge workshop he had spent much of his adult life in and, inevitably, the decline of crafts and trades in the U.K. He set the tone for the day: interested, insightful people testing and extending my knowledge in the nicest way possible.

 

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Medieval woodworking part 4: plank chest 2

Medieval woodworking part 4: plank chest 2

My nearest and dearest tell me that I have a lot of tools (they’re too polite to say “too many”). Each one, I say in my defence, has a purpose. No two are identical.

However there’s no doubt that there is some redundancy in the ranks. ‘Efficiency savings’ could be made. Some are more flexible than others. Chisels, for example can do a host of different tasks but require more skill to do some of those tasks well. Other tools perform only one task but they’re easier to use. Let’s take cutting a housing (dado if you’re American) as an example:

  1. Knife two parallel lines, chisel a wall to guide a saw, saw to depth, chisel out the waste (using a mallet), use a router plane to level the bottom. Six tools, one of which probably didn’t exist in medieval times.
  2. Clamp or nail a batten across the board. Use a dedicated dado plane to depth. Only two tools (if you don’t count the batten) but the clamps and dado plane are relatively recent inventions. The dado plane is about as dedicated a tool as you’ll find. It just cuts housings. At a specific width. Not adjustable.
  3. Clamp or nail a batten across the board. Spend half an hour setting up an electric router. Spend ten minutes finding and putting on protective clothing (mask, goggles, ear defenders, chainsaw trousers). Spend 30 seconds in abject, gibbering terror cutting the housing. Have a cup of weak tea while you recover.
  4. Get good with a chisel. ‘Knife’ the lines with the chisel, chop out the waste with the chisel. Level the bottom with the chisel.

IMG_3081I had two housings to cut. If this were not a masochistic act of reenactment and I were using a milder wood than oak I would have taken option 2. In the spirit of the thing I tried to only use tools I have evidence for having existed at the time. Option 4 it is.

Oddly I didn’t take a photograph of the result. It works but it’s not pretty.

Here’s the start of the second housing using option 1. I convinced myself that a plane, as they say, is just a chisel in a jig. Any idiot can find a video of Paul Sellers making a router plane with a block of wood, a chisel and a wedge on YouTube. What’s that you say? They didn’t have YouTube in the thirteenth century? Arrant pedantry.

With four rebates to cut I tried the chisel method again. This is easier than the housings. It’s a lot like cutting half blind dovetails but without the worry about nice crisp tails. I did even it up with a shoulder plane. And then used a moving fillister for the other three.

IMG_3101I marked the semi-circles for the feet with a pair of compasses. All period-correct so far. I’ve seen evidence of bow saws from the period but not a turning saw as such so I decided to see if I could form them with a saw, chisels and gouge. Kerfing went swiftly. Chiselling the waste out was quick as well. Fortunately I have a very large carving gouge at a fractionally quicker sweep than the chosen curve. Again – very straightforward.IMG_3116 I don’t think that a turning saw would have saved me a great deal of time and I’m much more confident with a gouge than a thin blade in 3/4″ of oak.

I did cheat a little bit and chamfered one curve with a spokeshave. The other I did with a chisel.

The only joinery left was to peg it all together. At this point I gained a lot of respect for the medieval joiner. The rebates on the ends of the front and back panels are there to help when assembling.

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Tight when made but worked a little looser by the time the chest was assembled.

Nevertheless unless the boards are dead flat and the rebates dead square putting this together without clamps would be next to impossible. I spent a lot of time with shoulder planes fettling every joint. A modern woodworker with good glues and a rack of clamps would pull a half millimetre gap closed and drive home a fastening, content in the knowledge that it wouldn’t show its seams before the customer got it home. The medieval craftsman had to get the joints perfect just to be able to drill the holes for the pegs. Some antique dealers use the word “primitive” to describe pre-industrial furniture with little ornamentation. One should earn the right to use that word about someone else’s work.

Sat astride my low workbench, the boards resting against pegs and being held by my knees I managed to drill a couple of holes. With a dowel at each end of the board holding it fast the others went in more easily. With a now-familiar sigh of relief I went back to my joiner’s bench and my clamps for the other three ends.

There’s surprisingly little joinery in a six board chest. With a jointer, thickness planer and a dado stack in a table saw (I wonder if the dado stack will be legalised in the U.K. Post-Bexit?) I imagine it would take less than an afternoon. For the pre-industrial craftsman with a frame saw, chisel, mallet and auger it’s a somewhat greater endeavour.

With the edges chamfered and the rougher grain scraped I put on some finish. The use of linseed oil was widespread in this period but its use on furniture is, as far as I know, undocumented. In the C12th Theophilus1 wrote in his treatise for artists that using linseed oil on wood is ‘tedious’. Boiling linseed oil to speed up polymerisation was known in the Middle Ages, as was adding lead to do the same thing, but Theophilus was apparently using it raw.

1. Theophilus (C12th) On divers arts Republished by Dover Art Instruction (2000)

Treenails

Several of the chests I’ve used to inform this demonstration have been put together with treenails (trenails/trunnels/pegs etc.) I’ve used pegs for drawbored mortice and tenon joints quite a lot. A dowel plate is traditional for pounding them to shape and I’ve had some success with this method. It’s noisy work and sometimes I don’t get the straightest pegs but it does have one structural advantage – the pegs follow the grain of the timber.

IMG_0795Last summer I visited the Viking Centre near Ribe in Denmark. I was delighted to see them using an identical method but for much larger pegs. Their living history exhibits draw on a substantial body of research and I’m assuming that there is evidence that this is historically accurate. I’d welcome your corrections if I’m wrong.

However I rarely use the plate anymore. For this task I’ve chosen the “workmanship of certainty” over “the workmanship of risk”1. Partly because it gives more consistent results, partly because it’s a lot quieter but mostly because I get to use a really great machine!

Pegs through scarf

Boring the holes at an angle draws the scarf together. So they say.

In the interests of full disclosure: some of the treenails used in this chest will be pounded out by hand in a thoroughly medieval fashion but most of them won’t be…

1. Pye, D. 1968 The Nature and Art of Workmanship

Medieval woodworking part 2

If I’m to demonstrate C13th woodwork I’ll need a bench. There’s no evidence, as far as I’m aware, that the waist-high joiners’ benches we know today existed in those time. Staked benches, both low and high, certainly did.

Once again Chris Schwarz’s Roman Workbenches and Vires’ Woodworking in Estonia provided some inspiration, measurements and guidance.

I’m not making any great claims to historical accuracy with this. It’s a fairly pragmatic step. People almost certainly sat on low benches and removed small bits of wood from bigger bits of wood. They still do. We’ll get to the interesting stuff (chests and chairs) soon but in the meantime here’s what I built:

 

Even professionals get it wrong

imageBefore I had the time and space (and skill and confidence?) to build such a thing my wife and I bought an oak sideboard. It purported to be made in England from domestic oak and I have no reason to doubt that. It’s got big, chunky, machine cut dovetails and the drawer fronts are applied. We still like it a lot. It’s a simple design with little decoration, nice proportions and is solidly constructed. The flat panels and simple, turned wooden pulls might be described as ‘Shaker’ by those who need to put a label on simple vernacular furniture.

At the same time we bought a ‘matching’ blanket box. It has an issue that I should have spotted even then. We were clearly carried away with the sideboard and didn’t pay enough attention. Those furniture salesmen eh? Wiley Devils. Here are the tops of both. Can you see the problem?

On the left is one panel of the top of the sideboard. The panel is fitted into an open backed frame and is rebated so that the surfaces of the panel and frame are flush. As the seasons change the panel expands and contracts and sometimes (as now at the end of a warm, damp summer) protrudes beyond the back of the frame. Because the grain is orientated so that it runs lengthways it will never expand along the length of the piece and so will never distort the frame. Good thinking sideboard-maker.

For whatever reason (lack of longer lengths of timber? ignorance? malice? who knows) the blanket box maker has orientated the boards so that they run front to back putting all of the expansion and contraction along the length of the box. Here is the result:

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By the end of winter that reveal is even. This tells us two things: the box was built in winter when the timber was at its least moist. And it was built by someone who didn’t know about (or care about?) seasonal movement.

Hoadley’s calculation for wood movement tells us that the change in dimension across the grain is equal to the initial dimension of the timber multiplied by the total shrinkage percentage of that species of wood multiplied by the product of the change in moisture content divided by the fibre saturation. There are going to be some estimates in this!

ΔDi=DS(ΔMC/fsp)

ΔDi=(31.5)(0.105)((0.28-0.22)/0.28)

ΔDi=0.95

This would be bad enough if I was working in centimetres but I’m using imperial! Almost an inch of potential movement. I’ve been fairly conservative in my estimates and we still end up with horribly large number. Some cabinet makers use a rule of thumb that wood will move up to 4% during the seasons. That’s 1 1/4 inches.

Note to self: Use narrow panels. Work out where the extra wood is going to go.

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When I made this panel at the start of the summer I broke the rules in the same as the way as the maker of our blanket box. The timber is flat sawn and so has more movement than vertical grain planks and the long grain runs in the shortest dimension.

Aware that I was breaking these rules I cut the groove in the frame deep and let the panel in half way into the groove.

It moves around a lot if you make it but it’s never going to show a gap or prise its frame apart.

 

 

Use the tool in your hand


My carving teacher used to admonish me to do as much work as I could with the tool in my hand. Carvers often have a lot of tools on their benches. Swapping between them uses time. Use the tool in your hand until you can do no more work with it, then change.

I’ve just cut 13 brackets for a chest. They each have two ends with five edges at each end. That’s 130 edges. I started by using a block plane (an old Record 018  in case you’re only here for the tools!) for the straight edges and a chisel, bevel down, for the curves. The block plane wasn’t gaining me anything. The straight edges are so short that keeping the plane flat and the cut even was as much effort as doing the whole thing with a chisel. So I did.

If you’re paring end grain chamfers here are some notes.

  • Pare along and up, never down.
  • Always pare towards an already chamfered edge. That’s what the first corner cut is for.
  • Bevel down on concave curves.
  • As always – a very sharp chisel makes this a lot easier.

Octagonalising…

Eight times as bad as antagonising? No. Turning square sections into octagonal sections. How many of us have to use it before it gets a place in the OED?

I’m reading The Anarchist’s Design Book at the moment. I’ve read the first four chapters and skimmed the staked furniture projects. One of Chris Schwarz’s contributions to chair making is finding ways to build them without a box fullof specialist tools. Most of the time this is helpful and appreciated. Rather than creating anarchy it democratises the craft. But sometimes a specialist tool can really help and won’t cost the earth.

Take for instance the process of turning tapered, square section legs into octagons. He quotes Charles Hayward’s method using compasses and a straight edge (since he’s just published two tomes of Hayward’s work it must have been fresh in his mind). It’s a lovely technique and is fun to do. If you’re only going to make one chair it’s great. If you are planning a run of them try this:

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Spar maker’s gauge

It’s called a spar maker’s gauge. When building masts, booms, gaffs, lugs, sprits, bowsprits, boomkins or any other pole a boatbuilder often starts with a square section piece of wood, tapers it at either end and then planes or saws the corners off to make it an octagon. It’s then a bit more planing with hollow planes and you’ve got a rounded spar.

Hayward’s compass trick wouldn’t work here. There are tapers at both ends and they aren’t uniform. Instead they use this gauge. Building it is a matter of a few minutes work. The gap between the dowels must be slightly larger than the largest diameter of the spar, or in this case, leg. The spacing is critical. It’s better explained here.

Last year, when I built a stool for my new workshop, I used it for the legs. Works a treat. You might prefer pencils rather than nails. If you plan to build more than one chair it will be worth it.