One Good Turn: A Natural History of the Screwdriver and the Screw Read online

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  CONTENTS

  Epigraph

  Chapter One: The Carpenter’s Toolbox

  Chapter Two: Turnscrews

  Chapter Three: Lock, Stock, and Barrel

  Chapter Four: The Biggest Little Invention

  Chapter Five: Delicate Adjustments

  Chapter Six: Mechanical Bent

  Chapter Seven: Father of the Screw

  GLOSSARY OF TOOLS

  ACKNOWLEDGMENTS

  ABOUT WITOLD RYBCZYNSKI

  NOTES

  TEXT ILLUSTRATION SOURCES

  INDEX

  to Shirley

  Heurēka! [I’ve found it!]

  —ARCHIMEDES

  CHAPTER ONE

  The Carpenter’s Toolbox

  THIS ALL STARTS with a telephone call from David Shipley, an editor at the New York Times. Would I write an article for a special millennium issue of the Sunday magazine? he asks. The end of the millennium is on many magazine editors’ minds, and I have had a number of such requests. Shipley explains that the theme of the issue is The Best of the Millennium. That sounds interesting. “What do you want me to write about?” I ask.

  “We’re hoping that you can write a short essay about the best tool,” he answers.

  I am a bit let down. The best tool is hardly as weighty a subject as the best architect or the best city, topics I could really sink my teeth into. Still, I have been working on a long biography and would welcome a break. Writing about the best tool of the millennium might even be fun.

  While David Shipley is speaking, I compose the essay in my head. There is so much to choose from: paper clips, fountain pens, eyeglasses. I have recently seen a portrait in the Pennsylvania Academy of the Fine Arts of Benjamin Franklin wearing round spectacles, a reminder that Franklin was the inventor of the bifocal. Yet eyeglasses are much older than the eighteenth century. The first reference to eyeglasses is in a sermon given by a Dominican friar in Florence in 1306. He mentions that eyeglasses were invented twenty years earlier, and that he has even spoken with the inventor, although he neglects to give his name.1 Medieval eyeglasses were only for farsighted people and were used for reading and writing. They were the first practical application of the new science of optics, paving the way for such far-reaching inventions as the telescope and the microscope. A key influence on literacy, astronomy, and biology, eyeglasses surely qualify as “the best tool of the millennium.” This is going to be easy.

  However, when I mention my idea to David, it becomes clear that he has something else in mind. He means tool in the literal sense—a handsaw or a hammer. So, not eyeglasses. He must hear the disappointment in my voice, and he points out that I once wrote a book about building my own house. That might make a good starting point, he suggests helpfully. All right, I say, I’ll think about it.

  —

  In my case, “building my own house” meant actually building it. My wife and I, with the occasional help of friends, mixed concrete, sawed wood, plastered walls, and installed plumbing. We did everything ourselves except the electrical wiring. Ever since my boyhood experiences with recalcitrant train sets, I have been thwarted by electricity. Despite my father’s patient explanations—he was an electrical engineer—and a college physics course, I never grasped the relationship between voltage, current, and resistance. Electricity, in fact, was a problem in our house-building project—there was none. We were building on a rural site about eight hundred feet from the road, and although we planned to bring in power, initially we could not afford the cost of a temporary line. Renting a gas-powered generator would be expensive, too—and noisy. I decided to build the framing and exterior of the house by hand. Once the basic structure was finished, which promised to take a year or two, we would bring in a line and hire a professional to install the electrical wiring.

  Does one of my carpenter’s tools qualify as the millennium’s best? I discount power tools. I had used a portable circular saw, a drill, and a sander for finishing and cabinetwork, but these are chiefly laborsaving devices. Not that productivity isn’t important. Ken Kern, the author of The Owner-Built Home, estimates that cutting all the two-by-fours for the frame of a small house would take seven full days using a handsaw, and only thirty minutes using a power saw.2 I appreciate the ease of cutting wood with power tools, but the result, while more quickly arrived at, is no different than if I use a handsaw. In any case, I enjoy working with my hands. One of the rewards of building something yourself—a house or a bookshelf—is the pleasure of using tools. Hand tools are true extensions of the human body, for they have evolved over centuries of trial and error. Power tools are more convenient, of course, but they lack precisely that sense of refinement. No doubt, if I spent my life hammering nails, I would feel differently about the virtues of a nail gun, say. Yet increasing the productivity of carpenters does not seem to me in the same category as the invention of entirely new devices such as eyeglasses.

  That leaves my box of hand tools. The tools required for the construction of a small wood-frame house fall roughly into four categories: measurement, cutting and shaping, hammering, and drilling. My measuring tools include a try square, a bevel, a chalk line, a plumb bob, a spirit level, and a tape measure. A little reading informs me that almost all these tools predate our millennium; indeed, most predate the first millennium of the Christian age. A Roman builder, or mensor aedificorum, was familiar with the try square, the plumb line, and the chalk line—all tools that were developed by the ancient Egyptians.3 The level, or libella, also an Egyptian invention, consisted of a wood frame resembling the letter A, with a plumb bob suspended from the apex. To level, the string was lined up with a mark in the center of the crossbar. Not as compact as my spirit level, perhaps, but obviously just as serviceable since A-levels continued to be used until the mid-1800s. The spirit level, with its sealed tube containing an air bubble floating in alcohol, was invented in the mid-1600s. It was first exclusively a surveying instrument—it took another two hundred years to find its way into the carpenter’s toolbox. For measuring length, the Roman mensor used a regula, or a wooden stick divided into feet, palms, twelfths or unciae (whence our inches), and digiti or finger widths. I have a yardstick, too, but most of my measuring is done with a retractable steel tape. That, at least, would impress my Roman counterpart, whose only compact measuring device was a one-foot bronze folding rule. Oak yardsticks were used in the Middle Ages, and folding rules, in ivory, brass, or boxwood, reappeared in the eighteenth century. I can’t find the origins of the tape measure, but I would guess that it was developed sometime in the late 1800s. I would be lost without my twenty-five-foot retractable tape measure, but it does not seem to me to qualify as the best tool of the millennium.

  I own several saws. The handsaw, too, is an ancient tool: archaeologists have found metal-toothed Egyptian saws dating back to 1500 B.C. They have broad blades, some as long as twenty inches, curved wooden handles, and irregular teeth. The blades are copper, a soft metal. To keep the blade from buckling, the Egyptian saw was pulled—not pushed. Pulling is less effective than pushing, since the carpenter cannot bear down on the cutting stroke, and sawing wood must have been a slow and laborious process.I The Romans made two important improvements. They used iron for the b
lades, which made them stiffer, and they set the teeth of the saw to project alternatively right and left, which had the effect of making the saw-cut—or kerf—slightly wider than the blade, allowing smooth movement.

  The Romans also invented the stiffened backsaw, whose blade is reinforced at the top. This prevents straight-through cuts, but the tool is useful for cabinetwork, especially when used in combination with a miter box. The most ingenious Roman addition to cutting tools is the frame saw. A relatively inexpensive narrow blade is held in a wooden frame and is kept taut by tightening a cord. Wooden frame saws worked so well that they remained the most common type of saw well into the nineteenth century (the principle of the frame saw survives in the modern hacksaw). In the mid–seventeenth century, a new type of saw was introduced in Holland and England. It had a broad, unstayed blade and a wooden pistol-grip handle. The rigid blade, originally made by rolling steel strips, makes a more accurate cut than a frame saw, and there is no frame to interfere with deep cuts. This effective tool became the basic modern handsaw. My workhorse is a twenty-six-inch Disston crosscut handsaw, with a skew-back blade, first introduced in 1874 by Henry Disston, a Philadelphia saw-maker. The open handsaw is a definite contender for best tool, but while it is certainly an elegant solution to an old problem, I think that David expects something a little more momentous.

  The chief shaping device of the carpenter is the plane. The box plane is nothing more than a holder for a chisel blade, but it marks an important moment in the evolution of hand tools. Unlike an adze or a chisel, which depend on the skill of the craftsman, the effectiveness of a plane is built-in; that is, the carpenter does not need to control the blade, he provides only the motive force. One historian has called the plane “the most important advance in the history of woodworking tools.”4 That makes it sound like a worthy candidate for best tool of the millennium. Unfortunately, I find that the plane, too, is a Roman invention.

  Chisels have more ancient origins. Bronze Age carpenters used chisels with both integral handles and socketed wooden handles in house and furniture construction. The first mallets, which resembled bowling pins, were pounded across the grain and had a short working life. Eventually, a handle was fitted to a separate head, whose harder end-grain made a more durable hammering surface. Heavy, long-handled mallets are called mauls. Eighteenth-century carpenters used a huge maul, known as the Commander, to drive together the joints of timber-framed houses and barns. The Commander has a head six inches in diameter and a foot long. I didn’t have anything that big, but I did use a steel sledgehammer to coax stubborn joists and studs into place.

  The most unusual hammer I own comes from a hardware market in Mexico City. Made in China, it is a “combination case opener,” that is, a packing-crate opener. Like the specialized shingler’s hammer, which combines a hammer and a hatchet, the case opener incorporates several tools: a hammer, a nail puller, a hatchet, and a crowbar. Mine must have been made in one of Mao’s backyard furnaces, for shortly after I bought it, one of the metal claws broke off as I was pulling nails. Nevertheless, I still have it. While I am unsentimental about most possessions, I have never thrown away a tool.

  I have always thought of combination tools as particularly modern gadgets—I am embarrassed to recollect that I once gave my father a screwdriver with a built-in flashlight as a Christmas present. In fact, the combination tool is ancient. The two oldest woodworking tools are the ax, for felling trees, and the adze—with its blade turned ninety degrees—used for dressing timber. A combination ax-adze was used by the Minoan civilization of Crete, which also invented the double-headed ax. The ax-adze was popular with Roman carpenters. The Romans, who invented forged iron nails, used another dual-purpose tool: the claw hammer. Pulling nails exerts heavy pressure on the handle, which risks being pulled out of its socket, or eye. Medieval English claw hammers sometimes had two metal straps that reinforced the connection to the handle. An American was responsible for the modern form of the claw hammer. In 1840, a Connecticut blacksmith, inspired by the adze, added a tapered neck that extended down the hammer handle, resulting in the so-called adze-eye hammer, which survives to this day.

  Ancient Egyptian woodworkers used wooden pegs instead of nails. They made the holes with a bow drill. The bow drill, probably adapted from a fire-stick, has a cord wrapped around the drill and held taut by a bow. Holding the drill vertically, the carpenter moves the bow back and forth, like a cellist, pressing down on alternate turns. Because the carpenter exerts downward pressure with only one hand—and the cord can easily slip—the bow drill is ineffective for heavy drilling. (Bow drills continued to be used for delicate drilling until the nineteenth century.) Moreover, since each drilling stroke is followed by an idle return stroke, the bow drill wastes energy. Once again, it was the Romans who found a solution: the auger. The auger has a short wooden cross-handle, attached to a steel shaft whose tip is a spoon-shaped bit. The carpenter, holding the handle with both hands, can apply both great rotational force and heavy downward pressure. A particular variation of the auger, developed in the Middle Ages for drilling deep holes in ships’ timbers, is called a breast auger. It is topped by a broad pad on which the carpenter rested the entire weight of his body.

  A medieval workman with his tools, including a carpenter’s brace. Detail from Bearing the Cross, part of an altarpiece painted by Meister Franke, 1424.

  The auger is a great advance, but it has one drawback: the bit tends to freeze in the wood between turns. The great breakthrough in drilling tools occurred during the Middle Ages with the invention of the carpenter’s brace. The brace holds the same spoon-shaped bits as an auger, but the handle is shaped in such a way that it is possible—for the first time in history—to drill holes with a continuous rotation. A rounded pad atop the brace enables the carpenter to push down on the bit as he turns with a smooth back-and-forth motion.

  One of the earliest representations of a brace is contained in the right-hand panel of an altar triptych painted about 1425 by the Flemish artist Robert Campin and now hanging in the Metropolitan Museum of Art in New York. The subject is Saint Joseph in his workshop. Joseph is making mousetraps (this is an allegorical painting), and he is surrounded by tools—a hammer and nails, a chisel, pincers, a straight saw, and an auger. He is holding a carpenter’s brace and is drilling a hole in a piece of wood that he awkwardly balances on the arm of his chair.

  What is striking about the tool that Joseph is holding is that it is identical to the eighteenth-century wooden braces I have seen in collections of American tools, and basically not much different from the brace in my own toolbox (although mine is steel). Some tools, such as hammers and saws, evolve slowly over centuries; others, such as planes, seemingly spring to life fully formed. The brace seems to have been such a case—it bears no resemblance to the auger or the bow drill. The brace has no antecedents because it incorporates an entirely new scientific principle: the crank. The crank is a mechanical device with a unique characteristic: it changes reciprocal motion—the carpenter’s arm, moving back and forth—into rotary motion—the turning bit. The historian Lynn White Jr. characterized the discovery of the crank as “second in importance only to the wheel itself.”5 The crank made possible not only the carpenter’s brace, but also hand-cranked mills and grinders, as well as a variety of water- and wind-driven machines such as stamping mills and pumps, and eventually steam engines.

  There is no material or textual evidence that the crank existed in antiquity—as far as we know, it is a medieval European discovery.6 The oldest representation of a crank is in a fourteenth-century medieval treatise that shows a design for a boat with a manual crank drive that resembles the kind of recreational foot-driven paddle-boat that is a staple of summer-cottage lakes and city parks.7 A Bavarian book on military engineering published in 1405 includes a sketch of a milling machine turned by a hand crank.8 At about the same time, cranked lecterns (similar to modern dentists’ adjustable tables) were used by scholars to swing books within convenie
nt reading range.9 So, around 1400, cranks were in the air. Whether the carpenter’s brace came first or was inspired by one of these other gadgets, there is no doubt that this simple tool was the first practical application of the crank on a broad scale. The origin of the name brace, incidentally, is obscure. The tool was first called a piercer, for it was used to drill starting holes that were then enlarged with an auger. One historian speculates that brace may refer to the metal braces that were sometimes added to reinforce the crank shape.10

  The carpenter’s brace is a good tool and it definitely belongs to our millennium. But, as far as my essay is concerned, there is a problem: the brace is, well, boring. Despite the importance of the crank, the carpenter’s brace itself never really developed further. The only nonwoodworking application occurred in the sixteenth century, when surgical braces, called trephines, were used to cut out a disk of bone from the skull. Otherwise, the brace seems to have had an uneventful history. It was merely a better way of drilling holes.

  —

  I have spent a week thinking and reading without making much progress. Since I am embarrassed to admit to David Shipley that I can’t come up with a subject, it’s beginning to look as if I will have to write about the unexciting carpenter’s brace. This is not going to be an easy assignment; what had seemed like fun is turning into a chore. Dejected, I mention my predicament to my wife, Shirley. She thinks for a moment and answers, “There is one tool that I’ve always had at home. A screwdriver.” I look at her skeptically. “Definitely, a screwdriver,” she says. “Wherever I’ve lived, I’ve always had a screwdriver in the kitchen drawer. Preferably the kind that has several interchangeable heads, or whatever those end pieces are called.” She adds conclusively, “You always need a screwdriver for something.”