The story of precision begins with metal.
And the story begins, according to Winchester, at a specific place and time: North Wales, “on a cool May day in 1776.” The Age of Steam was getting underway. So was the Industrial Revolution — almost but not quite the same thing. In Scotland, James Watt was designing a new engine to pump water by means of the power of steam. In England, John “Iron-Mad” Wilkinson was improving the manufacture of cannons, which were prone to exploding, with notorious consequences for the sailors manning the gun decks of the navy’s ships. Rather than casting cannons as hollow tubes, Wilkinson invented a machine that took solid blocks of iron and bored cylindrical holes into them: straight and precise, one after another, each cannon identical to the last. His boring machine, which he patented, made him a rich man.
Watt, meanwhile, had patented his steam engine, a giant machine, tall as a house, at its heart a four-foot-wide cylinder in which blasts of steam forced a piston up and down. His first engines were hugely powerful and yet frustratingly inefficient. They leaked. Steam gushed everywhere. Winchester, a master of detail, lists the ways the inventor tried to plug the gaps between cylinder and piston: rubber, linseed oil–soaked leather, paste of soaked paper and flour, corkboard shims, and half-dried horse dung — until finally John Wilkinson came along. He wanted a Watt engine to power one of his bellows. He saw the problem and had the solution ready-made. He could bore steam-engine cylinders from solid iron just as he had naval cannons, and on a larger scale. He made a massive boring tool of ultrahard iron and, with huge iron rods and iron sleighs and chains and blocks and “searing heat and grinding din,” achieved a cylinder, four feet in diameter, which as Watt later wrote “does not err the thickness of an old shilling at any part.”
By “an old shilling” he meant a tenth of an inch, which is a reminder that measurement itself — the science and the terminology — was in its infancy. An engineer today would say a tolerance of 0.1 inches.
James Watt’s fame eclipses Iron-Mad Wilkinson’s, but it is Wilkinson’s precision that enabled Watt’s steam engine to power pumps and mills and factories all over England, igniting the Industrial Revolution. As much as the machinery itself, the discovery of tolerance is crucial to this story. The tolerance is the clearance between, in this case, cylinder and piston. It is a specification on which an engineer (and a customer) can rely. It is the foundational concept for the world of increasing precision. When machine parts could be made to a tolerance of one tenth of an inch, soon finer tolerances would be possible: a hundredth of an inch, a thousandth, a ten-thousandth, and less.
Watt’s invention was a machine. Wilkinson’s was a machine tool: a machine for making machines and their parts. More and better machines followed, some so basic that we barely think of them as machines: toilets, locks, pulley blocks for sailing ships, muskets. The history of machinery has been written before, of course, as has the history of industrialization. These can be histories of science or economics. By focusing instead on the arrow of increasing precision, Winchester is, in effect, walking us around a familiar object to expose an unfamiliar perspective.
Can precision really be a creation of the industrial world? The word comes from Latin by way of middle French, but first it meant “cutting off” or “trimming.” The sense of exactitude comes later. It seems incredible that the ancients lacked this concept, so pervasive in modern thinking, but they measured time with sundials and sandglasses, and they counted space with hands and feet, and the “stone” has survived into modern Britain as a measure of weight.
Any assessment of ancient technology has to include, however, a single extraordinary discovery — an archaeological oddball the size of a toaster, named the “Antikythera mechanism,” after the island near Crete where Greek sponge divers recovered it in 1900 from a shipwreck 150 feet deep. Archaeologists were astonished to find, inside a shell of wood and bronze dated to the first or second century BC, a complex clockwork machine comprising at least thirty bronze dials and gears with intricate meshing teeth. In the annals of archaeology, it’s a complete outlier. It displays a mechanical complexity otherwise unknown in the ancient world and not matched again until fourteenth-century Europe. To call it “clockwork” is an anachronism: clocks came much later. Yet the gears seem to have been made — by hand — to a tolerance of a few tenths of a millimeter.
After a century of investigation and speculation, scientists have settled on the view that the Antikythera mechanism was an analog computer, intended to demonstrate astronomical cycles. Dials seem to represent the sun, the moon, and the five planets then known. It might have been able to predict eclipses of the moon. Where planetary motion is concerned, however, it seems to have been highly flawed. The engineering is better than the underlying astronomy. As Winchester notes, the Antikythera mechanism represents a device that is amazingly precise, yet not very accurate.
What makes precision a feature of the modern world is the transition from craftsmanship to mass production. The genius of machine tools — as opposed to mere machines — lies in their repeatability. Artisans of shoes or tables or even clocks can make things exquisite and precise, “but their precision was very much for the few,” Winchester writes. “It was only when precision was created for the many that precision as a concept began to have the profound impact on society as a whole that it does today.” That was John Wilkinson’s achievement in 1776: “the first construction possessed of a degree of real and reproducible mechanical precision — precision that was measurable, recordable, repeatable.”
Perhaps the canonical machine tool — surely the oldest — is the lathe, a turning device for cutting and shaping table legs, gun barrels, and screws. Wooden lathes date back to ancient China and Egypt. However, metal lathes, enormous and powerful, turning out metal machine parts, did not come into their own until the end of the eighteenth century. You can explain that in terms of available energy: water wheels and steam engines. Or you can explain it as Winchester does, in terms of precision. The British inventor Henry Maudslay made the first successful screw-cutting lathe in 1800, and to Winchester the crucial part of his invention is a device known as a slide rest: the device that holds the cutting tools and adjusts their position as delicately as possible, with the help of gears. Maudslay’s lathe, described by one historian as “the mother tool of the industrial age,” achieved a tolerance of one ten-thousandth of an inch. Metal screws and other pieces could be turned out by the hundreds and then the thousands, every one exactly the same.
Because they were replicable, they were interchangeable. Because they were interchangeable, they made possible a world of mass production and the warehousing and distribution of component parts. A French gunsmith, Honoré Blanc, is credited with showing in 1785 that flintlocks for muskets could be made with interchangeable parts. Before an audience, he disassembled twenty-five flintlocks into twenty-five frizzle springs, twenty-five face plates, twenty-five bridles, and twenty-five pans, randomly shuffled the pieces, and then rebuilt “out of this confusion of components” twenty-five new locks. Particularly impressed was the American minister to France, Thomas Jefferson, who posted by packet ship a letter explaining the new method for the benefit of Congress:
It consists in the making every part of them so exactly alike that what belongs to any one, may be used for every other musket in the magazine…. I put several together myself taking pieces at hazard as they came to hand, and they fitted in the most perfect manner. The advantages of this, when arms need repair, are evident.
As it was, when a musket broke down in the field, a soldier needed to find a blacksmith.
Replication and standardization are so hard-wired into our world that we forget how the unstandardized world functioned. A Massachusetts inventor named Thomas Blanchard in 1817 created a lathe that made wooden lasts for shoes. Cobblers still made the shoes, but now the sizes could be systematized. “Prior to that,” says Winchester, “shoes were offered up in barrels, at random. A customer shuffled through the barrel until finding a shoe that fit, more or less comfortably.” Before long, Blanchard’s lathe was making standardized gun stocks at the Springfield Armory and then at its successor, the Harpers Ferry Armory, which began turning out muskets and rifles by the thousands on machines powered by water turbines at the convergence of the Shenandoah and Potomac Rivers. “These were the first truly mechanically produced production-line objects made anywhere,” Winchester writes. “They were machine-made in their entirety, ‘lock, stock, and barrel.’” It is perhaps no surprise that the military played from the first, and continues to play, a leading and deadly part in the development of precision-based technologies and methods.
