By the time De Re Metallica was published, in the middle of the 16th century, mechanical engineering was well established. The woodcuts provided by Agricola’s text display a wide range of devices, including waterwheels, gears and simple pulleys. This kind of technology harnesses a force, and either magnifies it or converts it into a different force. For example the waterwheel could be used to turn millstones, even though the wheel is vertical and the millstone horizontal. It was this ability that gave rise to the complexities of the Industrial Revolution.
If we go back 400 years, many of these technologies had existed in one form or another; the historical records seems to contain less direct evidence, but wind- and watermills existed, and had some internal gearing. The 16th century woodcuts also show men and livestock being used to power devices, and these sources would have been just as available in the 12th century or before. While studying this subject, I came across an interesting series of blog posts about The Great Machine, which goes into a fair amount of detail about animal-driven wheels for this period.
For the medieval jeweller, the impact of these technologies would be minimal. What seperates the goldsmith from the miller, or even the miner, is scale of their work. While grain and ore was processed on a very large scale, jeweller’s workshops were smaller affairs, and in the early middle ages, before 1000AD, many craftsmen were itinerant, travelling from one town to another, plying their trade. When labour was cheap, as it must have been then, it was better to have an apprentice hammer out a sheet of silver than it was to design a water-powered rolling mill to achieve the same ends. It might be that the same applied for other metalworking; the first powered rolling mill appears to have been built at the end of the 1500’s.
Although gold- and silversmiths had little need for the power provided by water, wind or muscle, they had access to some workshop devices. Theophilus describes quite a few. Of particular importance to these is the handcrank. When using the Durston rolling mill at work, the crank I turn has a system of internal gearing to translate the force. In the early middle ages, machinery generally seems to work without gearing. Just having a flick through On Divers Arts, there are five obvious examples of “lathes” – for making pipes for an organ, for turning a grindstone, for turning cast bells, for cutting grounds in iron, and lastly a pewterer’s lathe; while the first four are all hand-turned, this one is driven by a strap, in the style of the bow lathe (pictured left is a woodturner using a bow lathe) although in this case, Theophilus suggests using a boy to pull the ends of the strap.
Another rotary system that Theophilus describes has a vertical axis. I mentioned these on the post on drills recently. As above, one was hand-turned, and the other driven by a leather strap. These were intended for grinding small quantities of gold powders and almalgams.
As a guide line, any mechanical assistance I use must be simple, must avoid the use of gears, and must be made of wood. A pole lathe certainly fits this description, and I’ll look at building one at some point in the future. Another possibility is the grindstone; at the very least, I could build a small version that can take modern grinding wheels. Before that, if I have any projects that have to use a rotary machine, then we do have a (non-functional) lathe at work. If I can get that going, I should be able to run it at a very low speed. The machine that I’ll really miss is the modern jewellers lathe, which I use for polishing. At slower speeds, the combination of mops and abrasives wouldn’t work fast enough to be usable.