I made a collapsible spring pole lathe last year. This was more than just a project for a Society for Creative Anachronism (SCA) arts and sciences competition, it was also a tool which I could use to make more authentic-looking turned items, such as tool handles, chair legs, and game counters. With a maximum working length just over two feet, I cannot turn table legs on this lathe, but I can turn all sorts of small items.
Why would anyone want to build a spring pole lathe? They operate on manual power in a reciprocal pattern, meaning that when the turner pushes down on the foot pedal, the spring pole flexes as the wood turns toward the chisel to allow for a quick cut before the end of the pedal’s range is reached, then as the pedal is released, the flexed pole springs back up, rotating the wood away from the chisel and returning the pedal to an elevated position for the next cut. This means each work turned on a spring pole lathe is the product of many small, quick cuts. The results may vary from those of turning a similar project on a continuous motion lathe. Modern lathes, for instance, use a motor that keeps the lathe turning continuously in the same direction, usually at a fairly constant speed. Even 16th-17th century flywheel lathes, which used a foot-powered treadle to turn a flywheel, were able to maintain a relatively consistent speed thanks to the flywheel’s ability to preserve momentum. I saw one of these at Estrella War last year, and it was truly a marvel of Renaissance technology (in fact, it narrowly beat my lathe in the “machines” category in the arts and sciences contest). So with such superior technology available by the end of the middle ages, why would anyone want to build a spring pole lathe?
- It is lightweight and portable.
- I can collapse it down into about a 2-sq ft footprint in my garage, so my wife’s car still fits in the garage and I don’t have to sleep on the couch.
- It breaks down small enough to fit it into my friend’s Prius, along with all of my armor and both our camping gear, and we didn’t have to figure out how to strap a giant wheel onto the roof without scratching the car or risk losing the flywheel on the long drive to war.
- I can take it with me to war events and turn out small projects, to demonstrate how wood turning was done in period.
- I can make small turned objects, like game counters and tool handles, with an authentic hand-worked look, rather than the polished look that results from turning on a high-speed modern lathe.
Of course I realize that these are purely modern considerations that did not apply to medieval turners and carpenters. This brings me to another point: probably most medieval turners did not build their own lathes. Division of labor predominated medieval production methods, and I doubt anyone who was not a member of the joiners’ guild (i.e. anyone who was not a carpenter) would have built a lathe. Still, I found myself designing a lathe to do something few other lathes have ever been required to do, which is to be dragged around to events to turn out medieval-looking projects.
First, I looked at medieval graphic representations of lathes. These come from sketches, paintings and manuscripts mostly dating from the 15th and 16th centuries. One of the first problems I identified in my medieval lathe project was that medieval lathes were not portable (at least I have not seen any evidence of a portable lathe earlier than the 18th century). In the middle ages, it seems, the turner went to his shop, he did not roam around bringing the shop with him. Short of holding SCA events at my house, however, I would need to make my lathe portable, so that it could be broken down, loaded into a car, carried to an event site, and set back up for use. Another constraint was that (up to this point in time) I have neither the tools and resources, nor the knowledge and experience, to incorporate any blacksmithing work into my woodworking, so I made this lathe almost entirely out of wood. The only metal parts are the centers, which I purchased. The only other non-wood part is the cord, which I will talk more about later.
Here we see a German turner (Holzdrechsler in German) from the late middle ages (16th century?). The lathe bed appears to be carved from a single beam (probably about 10cm x 10cm, about a meter long). Note the butt board behind the turner, which was a relatively late invention. I see that one of the upright posts of the lathe frame extends right up into a stationary headstock, and the tailstock is movable along the lathe bed and secured to it with a tusk tenon. My design essentially grew from a development of this design, incorporating some elements of a much later design known as the Hulot lathe. A final note I would like to make about this lathe is that the tool tray you can see below the turner’s right hand inspired me to equip my lathe with a removable tool rack. This tool rack is designed to be removable in order to prevent breaking during transport, attaching by means of two 3/8″ dowels, which fit into corresponding holes on the face of the lathe bed rail.
This earlier design shows some important differences from the later period lathe pictured above. This one shows a turner from Nürnberg, circa 1425, but I have found some apparent inconsistencies in this sketch which cause me to question its technical accuracy. One of the first things I noted about this image was the presence of a mast for mounting the spring pole, seemingly creating an artificial tree inside the shop (which brought to mind the idea that early lathes probably amounted to a table with a slit, placed under a tree and equipped with a pedal, using a live limb in the tree as a spring pole). At any rate, the glaring inconsistency I see here is that the immovable mast and the pedal (which appears to be hinged to moorings set into the floor boards) do not allow for lateral adjustment, so the stationary headstock should be placed between these two immovable points, yet it is the moveable tailstock that is shown in that position. If those two points are immovable and the tailstock is obliged to remain between them, it defeats the purpose of making the tailstock mobile. At any rate, the main reason I wanted to include this image is because it inspired probably the single most important improvement to my lathe design. (More about that in a minute!)
This lathe, designed by a French toolmaker named Hulot around 1775, was revived by the Woodwright Shop. While it certainly incorporates some post-Renaissance design elements (such as the moveable toolrest, the internal spring pole and overhead lever, and the adjustable tension system), I felt more comfortable incorporating other design elements present here, most notably the through tenons and wedges. I felt it was important to keep the spring pole overhead, however, because I have seen absolutely no evidence of an internal spring pole earlier than 1775. Still, the full-height tail post with the spring pole mounted directly to it was an elegant solution to my need for a compact, self-supportive design that could be set up anywhere.
In designing my lathe I settled on ash as an ideal wood for its light weight and hardness, making it the ultimate hardwood for durability in a piece of portable furniture. I decided early on to make 2-ft long feet for stability during use, and I toyed with the idea of using a mortise and tenon joint to attach these, with removable pegs for reinforcement, so that the pegs could be pulled out to free the mortises during breakdown. Ultimately I decided that extra step in break-down was unnecessary and the stability during use was more important than the absolute smallest possible breakdown. My frame basically consisted of three crossmembers with long tenons at both ends, extending through mortises cut through two upright planks. These are secured in place with wedges, passing through the tenons. In order to resolve the problem of making a self-contained spring pole lathe which could be set up indoors as well as outdoors, I decided to incorporate the headstock into one upright and the spring pole mast into the other, with the spring pole arching over the full length of the lathe to place the drive cord near the headstock. So far the design was coming along just great, as everything seemed to be falling into place just right. I was up many late nights working in the garage to make all these enormous cuts by hand with a coping saw, cutting through 6/4″ thick ash wood, and I spent untold hours shaving and scraping the mortises to fit the joinery just right, so that everything fit snugly. But everything was coming together just fine. I got the last of the work done the night before Outlands Queen’s Prize.
Joseph Moxon’s lathe, circa 1678, pictured here, shows a framing design broadly similar to mine. This is a significant departure from 14th-early 15th century lathes, which were built around a lathe bed cut from a single slab in a four-legged table style. This sketch also includes another important clue omitted from the first image above. Note the shackle, presumably mounted to the rafters of the shop, through which the spring pole passes. While I was at Queen’s Prize, my spring pole flexed well initially but soon wobbled loose and started to break down inside the hole where it mounts into the upright plank at the tail end of my lathe. I believe it was Don Domin and Master Friedrich Wilhelmssohn who pointed out the reason for this mechanical failure and the true purpose of the stiffening arm seen in the 1425 Nürnberg lathe as well as the shackle seen above Moxon’s lathe. These are not for securing or stiffening so much as for shifting the fulcrum away from the point of attachment.
It must be remembered that a spring pole is not only intended to flex, but for better or worse it acts as a lever. Like any lever, it must have a fulcrum at some medial point between the point of attachment and the load (in this case, the cord pulling down with each push of the turner’s foot on the pedal). Since my fulcrum was at the point of attachment, it failed as a lever and behaved like a wobbly chair leg – the more it wobbles the looser it gets, the looser it gets the more it wobbles, until it fails and breaks. I needed a “support arm” like the one seen in the Nürnberg lathe, not to stiffen the attachment so much as to provide a fulcrum to shift the downward stress of flexion away from the upward stress of leverage. Thus, I came up with a support arm passed through a mortise cut at a severe angle through the upright post, and I quickly realized that this would need a pin set at 90 degrees to the support arm, to secure it against the downward stresses of spring pole flexion. Finally, I arrived at the design you can see here, and I have not had any further problems with mechanical failure since this improvement.
Another improvement I have made is a “quick release” toggle for the drive cord. Drive cords for lathes in the middle ages were usually made of “cat gut” (which is not actually cat intestine, like it sounds; rather, this is actually sheep intestine), and I found that an appropriate weight of natural “cat gut” (sheep intestine) cord can still be purchased as this is still used by historical purists as a drive cord for grandfather clocks, but only two cords would cost me about $50, so I opted for Tandy Leather‘s artificial sinew instead, because I can get a 300-yard spool for only $20, and that is plenty to make dozens of drive cords. I make the cords by cutting about nine yards of the artificial sinew, doubling it, twisting it tightly, then doubling it again and counter-twisting it to make a cord composed of four thicknesses of the sinew, with a final length of about six feet. I tie a loop into each end and hook one of these on the foot pedal, putting the loop at the other end over the toggle suspended from the spring pole. The biggest way this helps is by allowing the short cord on the toggle to be wrapped one, two, or three times around the spring pole, in order to fine tune the amount of foot pedal travel according to the diameter of the piece of wood being turned. This way, no matter the size of the piece of wood (which the cord has to be wrapped around) I will still be able to get a full turn out of each stroke of the pedal.
Since tool rests on medieval lathes are poorly documented, I decided to put a piece of 1″ x 2″ (3/4″ by 1-1/2″ actual dimensions) hickory to act as a very simple tool rest. If I had this project to do over, the one thing I would do differently is to set the shoulders of the lathe at about the same height as the centers, so that the tool rest height is closer to the middle of the piece being worked. Having the tool rest a little lower isn’t the end of the world, it just means I have to adjust the angle of my chisel accordingly, so I drop the butt of the handle a little lower, which brings the tip up a bit, but I think this makes my hold on the chisel a tad less steady. I already turned a few things on this lathe, and I can say with confidence that it works. One of the first things I turned on the lathe was that little hourglass shaped toggle you see above, which was cut from a scrap of the same ash wood the lathe was made from. I also turned a set of 12th century style chess pieces. I will post the chess set later this week, so come back for that later!