Consider, for a moment, the humble screw. Behold its elegant, threaded body, tapering to a sharp gimlet point. Notice the head, with its single or perhaps cross-notched slot. And marvel.
For this seemingly innocuous little scrap of metal is an elegant piece of precision engineering, an object shaped by industrial history and beautifully designed for its job, being far more effective than a nail when it comes to fastening two pieces of wood. Nails are held in place by pressure from the surrounding wood fibres, but a screw is secured by a strong mechanical bond - yet a nail is difficult to remove, whereas a screw is easily, well, unscrewed.
Not being much of a DIYer, I had never given screws a second thought - until, that is, I read Witold Rybczynski's One Good Turn - A Natural History of the Screwdriver and Screw.
Rybczynski's delightful little book began in 1999 as one of those "end of millennium" projects, when an editor at the New York Times asked him for an essay on the best tool of the past 1,000 years. After much rummaging in his toolbox, he emerged despondent. All of the tools that he considered turned out to be quite ancient, many of them even prehistoric.
Ancient Romans
The hammer? Neanderthal. The chisel? Bronze Age. Drills and hand-saws? Used in Egypt 5,000 years ago. The auger and plane? Invented by the ancient Romans, who were also familiar with the plumbline, tri-square and leveller. Combination tools are also ancient, the ax-adze being a prehistoric forerunner of the Swiss Army knife.
And the screwdriver? So "laughably simple" that Rybczynski initially ignored it, until he realised that the screwdriver was nothing without a screw.
Which set him pondering: when were screws invented? The principle of the screw, or threaded cylinder, was known to the ancients and probably invented by Archimedes. That great mathematician, military engineer and inventor gave us, among other things, the compound pulley, windlass and ray gun (he used mirrors to focus the Sun's rays on to enemy ships), as well as the water screw, a device for lifting water that has at its heart an elegant helical screw.
About 300 years later, in the first century AD, Hero of Alexandria invented the vertical press, which incorporated a similar screw, and was used to press olives and grapes. But it was another 1,400 years before some bright spark realised that the same principle could be used to make an effective fastener.
Rybczynski's search for the earliest screw fastener becomes part of his story, for it is not easy to trace an idea backwards. His research brings him to military museums, and collections of historic implements, but mostly this is a paper chase, taking in 19th-century tool catalogues, 18th-century encyclopaedias, 17th-century DIY pamphlets, and medieval military treatises.
Milling machine
Most helpful are the illustrations and woodcuts. Agostine Ramelli's book on Italian military engineering and weapons, for instance, published in 1588, carries a depiction of a milling machine, the iron legs of which are clearly shown screwed on to a base using slot-head screws. And a book on German mining technology published 30 years earlier includes a drawing of a bellows, where again the leather is shown fixed to the frame with screws.
The earliest screw Rybczynski can find appears in a manuscript written in the late 1400s, and known as the "Medieval Housebook": one illustration shows a leg-iron fastened with slotted screws, but significantly, also a sketch of a screw on its own, suggesting that the screw itself is something of a novelty.
What most surprises Rybczynski is that the leg-iron is made of metal, and therefore the screw must mate with a matching threaded hole. Such a pairing requires considerable precision, and this realisation starts him on a second theme - how to make a screw and its matching hole. Not an easy matter, it seems.
Until the late 1700s screws were hand-made and expensive, the thread on each one individually cut from a nail-like blank. And nuts and bolts were made for each other, literally: each pair was unique, the nut fitting only that bolt, and vice versa.
The first screw-making machines were like a lathe, where the blank was held and the cutting bit was guided by a master wooden screw. By the 1800s, factories were churning out tonnes of cheap, machine-cut and precision-engineered screws of varying sizes, as well as uniform nuts which could fit any bolt of the same size. It was this precision and uniformity which, Rybczynski argues, made possible the Industrial Revolution.
The simple slot-head screw, however, is less than ideal, as the screwdriver can easily slip and strip the slot. So from the 1800s inventors sought various ways to improve the fit. In 1907 the Canadian Peter Robertson invented a novel screw with a socket head. Robertson's square socket has chamfered edges and a pyramidal bottom; the matching square-headed screwdriver fits snugly, and never slips.
Cruciform socket
Robertson screws are still popular with North American woodworkers, and if it had not been for the first World War, and Robertson's lack of business sense, we might all be using them now. Instead, we are more likely to use a Phillips screw, with its cruciform socket, patented in 1936 by one Henry Phillips from Oregon (and not as I used to think by Philips the Dutch electrical company; there is, I now realise, an ell of a difference).
Phillips's design is not as good as Robertson's: the screwdriver doesn't fit as snugly - but strangely, this is something of an advantage, as it means it is difficult to over-tighten a Phillips screw. General Motors tried Phillips's invention in 1936, and was so pleased it switched over completely, and the Phillips screw quickly became the industry standard.
All this and more you can read about in One Good Turn. Now, I don't suppose anybody knows where I can buy Robertson screws in Dublin?