One Good Turn: A Natural History of the Screwdriver and the Screw (8 page)

Meanwhile, American automobile manufacturers followed Ford’s lead and stuck to slotted screws. Yet the success of the new Robertson screw did not go unnoticed. In
1936
alone, there were more than twenty American patents for improved screws and screwdrivers. Several of these were granted to Henry F. Phillips, a forty-six-year-old businessman from Portland, Oregon. Like Robertson, Phillips had been a traveling salesman. He was also a promoter of new inventions, and acquired patents from a Portland inventor, John P. Thompson, for a socket screw. Thompson’s socket was too deep to be practicable, but Phillips incorporated its distinctive shape—a cruciform—into an improved design of his own. Like Robertson, Phillips claimed that the socket was “particularly adapted for firm engagement with a correspondingly shaped driving tool or screwdriver, and in such a way that there will be no tendency of the driver to cam out of the recess.”
¹¹
Unlike Robertson, however, Phillips did not start his own company but planned to license his patent to screw manufacturers.

All the major screw companies turned him down. “The manufacture and marketing of these articles do not promise sufficient commercial success” was a typical response.
¹²
Phillips did not give up. Several years later a newly appointed president of the giant American Screw Company, which had prospered on the basis of Sloan’s patent for manufacturing pointed screws, agreed to undertake the industrial development of the innovative socket screw. In his patents, Phillips emphasized that the screw was particularly suited to power-driven operations, which at the time chiefly meant automobile assembly lines. The American Screw Company convinced General Motors to test the new screw; it was used first in the
1936
Cadillac. The trial proved so effective that within two years all automobile companies save one had switched to socket screws, and by
1939
most screw manufacturers produced what were now called Phillips screws.

The Phillips screw has many of the same benefits as the Robertson screw (and the added advantage that it can be driven with a conventional screwdriver if necessary). “We estimate that our operators save between
30
and
60
percent of their time by using Phillips screws,” wrote a satisfied builder of boats and gliders.
¹³
“Our men claim they can accomplish at least
75
percent more work than with the old-fashioned type,” maintained a manufacturer of garden furniture.
¹⁴
Phillips screws—and
the familiar cross-tipped screwdrivers—were now everywhere. The First World War had stymied Robertson; the Second World War ensured that the Phillips screw became an industry standard as it was widely adopted by wartime manufacturers. By the mid-
1960
s, when Phillips’s patents expired, there were more than
160
domestic, and
80
foreign licensees.
¹⁵

The Phillips screw became the international socket screw; the Robertson screw is used only in Canada and by a select number of American woodworkers.
^II
A few years ago,
Consumer Reports
tested Robertson and Phillips screwdrivers. “After driving hundreds of screws by hand and with a cordless drill fitted with a Robertson tip, we’re convinced. Compared with slotted and Phillips-head screwdrivers, the Robertson worked faster, with less cam-out.”
¹⁶
The explanation is simple. Although Phillips designed his screw to have “firm engagement” with the screwdriver, in fact a cruciform recess is a less perfect fit than a square socket. Paradoxically, this very quality is what attracted automobile manufacturers to the Phillips screw. The point of an automated driver turning the screw with increasing force popped out of the recess
when the screw was fully set, preventing overscrewing. Thus, a certain degree of cam-out was incorporated into the design from the beginning. However, what worked on the assembly line has bedeviled handymen ever since. Phillips screws are notorious for slippage, cam-out, and stripped sockets (especially if the screw or the screwdriver are improperly made). Here I must confess myself to be a confirmed Robertson user. The square-headed screwdriver sits snugly in the socket: you can shake a Robertson screwdriver, and the screw on the end will not fall off; drive a Robertson screw with a power drill, and the fully set screw simply stops the drill dead; no matter how old, rusty, or painted over, a Robertson screw can always be unscrewed. The “biggest little invention of the twentieth century”? Why not.

I.
At the beginning of the nineteenth century, handmade nails were replaced by cut nails, stamped out of sheets of wrought iron (later steel), with a similar rectangular cross-section. Cut nails are sharpened by hand with a file.

II.
Starting in the
1950
s, Robertson screws began to be used by some American furniture manufacturers, by the mobile-home industry, and eventually by a growing number of craftsmen and hobbyists. The Robertson company itself was purchased by an American conglomerate in
1968
.

I
N READING ABOUT
the Wyatt brothers’ factory in Staffordshire, I had been struck by the statement that their screw-making machines were operated by children. During the eighteenth century, children commonly worked in coal mines, workshops, and factories, but were usually given only menial tasks. Even a machine as simple as a screw girder’s spindle required an experienced—not to say strong—operator. The Wyatt machines were obviously different. I had stumbled on a landmark of industrialization.
¹
At a remarkably early date—the industrial revolution would not get fully under way for another hundred years—the Wyatt brothers not only pioneered the use of multipurpose machines to achieve mass production, they were the first to put into place the guiding principle of industrialization. Their factory was the earliest example of an industrial process designed specifically to shift control over the quality of what was being produced from the skilled artisan to the machine itself.

The screw girder’s spindle and the Wyatt brothers’ screw-making machines are both examples of simple turning-lathes. In a lathe, the blank, or workpiece, is rotated around an axis, somewhat like a potter’s wheel. However, while a potter creates a shape by building up clay, the turner removes material. As the workpiece turns, a sharp cutter is applied to the surface and, depending on the desired shape, removes inequalities until every part is equidistant from the axis. The lathe is an ancient tool that appears to have been invented in Europe, since the earliest surviving pieces of lathe work are an eighth-century
B.C.
Etruscan bowl, and a sixth-century
B.C.
bowl found in Upper Bavaria.
²
Although these wooden objects were definitely turned, nothing is known of the lathes themselves. Turning technology eventually spread to the rest of the Mediterranean world, including Egypt, where the oldest depiction of a lathe, dating from the third century
B.C.
, has been found in a bas-relief on a grave wall. The piece being turned, which appears to be a furniture leg, is held vertically. The turner’s cutting tool resembles a chisel; his assistant rotates the piece by pulling a cord looped around the rotating axle, or mandrel. Since the workpiece rotates in alternate directions, the turner cuts only on every other turn.

The Egyptian bas-relief shows the turner and his assistant kneeling on the ground. It reminds me of my first visit to India, when I saw a carpenter at work squatting
on the floor. Just as the world is divided into those who wrap and those who button up, or those who eat with their fingers and those who eat with utensils, it is divided into craftsmen who work kneeling, squatting, or sitting on the ground, and those who work erect—or sitting—at a bench. The ancient Egyptians belonged to the former category; the Romans, to the latter. Since the Romans invented the plane, they needed a flat surface to which the workpiece could be fastened, and the result was the first carpenter’s bench.

Although Europeans in the Middle Ages often relaxed by sitting on cushions on the floor in the Oriental manner, they worked erect. This habit probably prompted the thirteenth-century European invention of the so-called pole lathe. The turner works standing up at a pole lathe. The workpiece rotates not vertically but horizontally. A cord is looped around the mandrel with one end attached to a hinged treadle, and the other fastened to a flexible pole, resembling a bowed fishing rod, that keeps the cord taut. The turner, alternately pressing and releasing the treadle with his foot, now has both hands free to guide the long-handled cutter, which he braces under his arm or over his shoulder for added stability. Like the Egyptian lathe, the pole lathe turns back and forth.

Screw-cutting lathe, from
The Medieval Housebook of Wolfegg Castle,
c.
1475
–
90
.

The simple pole lathe was used by wood turners for a long time—working examples survived in England until the early
1900
s. For turning metal, however, a more effective machine was required. Here the screw again plays a vital role, for the ancestor of the modern lathe is in fact a machine for cutting screws. It was invented almost three hundred years before the Wyatt brothers’ screw-making lathes and appears in the
Medieval Housebook,
the fifteenth-century manuscript that I had consulted in the Frick Collection. The beautiful drawing is precise. The lathe, a radical departure from the pole lathe, consists of a heavy frame mounted
on a solid workbench. The blank is held horizontally between two adjustable supports and rotated by turning a hand crank. One end of the blank is attached to a lead screw. As the blank turns, the lead screw advances through a threaded hole in one of the supports and pushes the blank through a box containing a sharp cutter that incises the thread. The operator has only to set up the blank in the jig, wedge the threaded support and the cutter-box in place, adjust the depth of the cutter, and turn the crank.

The
Housebook
lathe is made of wood, but it is a true machine tool; that is, it is a tool in which the machine—not the craftsman—controls the cutter.
³
It anticipates many features of the modern bench lathe: the two supports (today called a headstock and a tailstock); the frame (ancestor of the modern slide-rest) that allows flexibility in the location of cutter-box and stocks; a continuous drive that can be connected by a belt drive to an external power source such as a waterwheel; a rotating lead screw that advances the blank by tiny increments; a design that integrates the lathe with the workbench; and heavy construction that assures rigidity and a relatively high degree of precision.

The drawing of the lathe appears on the same manuscript page of the
Medieval Housebook
as the manacles, wrenching tools, and slotted screws. The slotted screws, which are tapered, were obviously filed by hand; the
lathe was used to turn the long wrought-iron screws that are part of the wrenching tools. It is several weeks since I visited the Frick, but I still have an illustrated catalog from the exhibition, and I examine the drawing of the lathe closely, trying to understand how it works.
⁴
The pointed cutter, which must have been tempered steel, is threaded to enable the operator to adjust the depth of the cut. It would have taken many passes to cut a thread into a hard wrought-iron rod. After each pass, the workpiece was retracted, the cutter was tightened to cut a deeper groove, and the operation was repeated. A lengthy process, but one that probably produced a reasonably accurate screw.

The drawing of the lathe includes a short-handled tool lying on the workbench. At first I assume that it is some sort of chisel or gouge. But as the exact functioning of the lathe becomes clearer, it is obvious that a chisel plays no part in the process. The author of the
Medieval Housebook
is thorough and his drawings do not usually contain extraneous information. While beautifully composed, these are technical documents that carefully describe how the various machines work, and exactly what tools are needed to operate them. A view of a spinning wheel, for example, includes a couple of empty spools. So what is the function of the mysterious tool? One day, while I am puzzling over the drawing again, I realize that the blunt end is exactly the same size
as the slot in the head of the cutter. Of course. It’s not a chisel, it’s used to adjust the cutter. It’s a screwdriver.

Eureka! I’ve found it. The first screwdriver. No improvised gadget but a remarkably refined tool, complete with a pear-shaped wooden handle to give a good grip, and what appears to be a metal ferrule where the metal blade meets the handle. Since the
Housebook
was written during the last quarter of the fifteenth century, there is no doubt that a full-fledged screwdriver existed three hundred years
before
the tool portrayed in the
Encyclopédie.
This confirms what I had suspected: the screwdriver and the screw were invented at about the same time. My guess about fifteenth-century armorers and gunsmiths was not far off the mark either. The
Housebook
lathe is illustrated in a chapter devoted to the technology of war, so it is likely that screwdrivers appeared first in military workshops, though perhaps not in France, as I had assumed, but in Germany.
^I