Screwdriver

How it works

The user grips the handle and turns it; the tip, seated in the slot or recess of the screw head, transmits that turning force to the screw. A wider handle lets the hand apply more torque, and the user presses along the axis of the shaft to keep the tip seated.

A slotted tip drives through two flat faces in a single slot and can slide out sideways. Recessed drives (the square socket and the cruciform) engage the tip on several faces at once and center it on the axis of the screw. Phillips’s 1936 patent describes its purpose in those terms: the screw is centered on the driver at the start and throughout its advance, and is held on the end of the driver before it is presented to the work.

Anatomy

Handle: Wood, later plastic or composite; the London pattern of the nineteenth century used an oval boxwood handle.
Ferrule: A metal collar at the front of a wooden handle that keeps it from splitting where the shaft enters.
Shaft (blade): Round or flat steel bar; on the London pattern the shaft is flattened and flared toward the tip.
Tip: The working end, ground to fit one drive type and size.

Variants

Slotted (flat-blade): The original form, for a single straight slot.
London pattern: A nineteenth-century English form with a flat, waisted blade and oval boxwood handle; the Science Museum Group holds an example from a shipwright’s chest of 1845–1855 and a 10-inch example from a 1926 maker’s catalog.
Square-socket (Robertson): For a tapered square recess; patented in Canada by P. L. Robertson and widely used mainly in Canada.
Cruciform (Phillips): For a cross-shaped tapered recess; developed from John P. Thompson’s patent, which was assigned to Henry F. Phillips.
Screwdriver bit: A tip without a handle, held in a brace, a bit holder or a powered driver. The Science Museum Group holds turnscrew bits dated 1840–1870.

Specifications

Tip size · drive-specific number or blade width: Each drive type has its own size series; a tip must match the recess.
Blade length · in or mm: The Science Museum’s 1926 London turnscrew is cataloged as 10-inch.

Made to

ASME B107.600
IEC 60900

Safety and care

Safety

Phillips’s 1936 patent describes the slotted blade leaving the slot during power-driven work as dangerous to the operator and injurious to the work.

Tips

Match tip size and type to the screw
The Army, Air Force, Navy and Marine Corps manual states the rule as always matching the size of the screwdriver to the job and the type of screwdriver to the head of the screw. For jeweler’s screwdrivers it adds that a screw too large for the tip will damage the tip.1
Drill a pilot hole first
The manual calls for a pilot hole made with a screw starter, awl, nail or drill before a screw is driven into wood, and for a drilled pilot hole in sheet metal. Light sheet metal can be pierced with a nail or punch.1
Start a screw with a holding driver, then change drivers
Common screwdrivers with a clip or sliding collar hold the screw on the blade for work in close quarters, overhead and in hard to reach places. The manual says to switch to a conventional screwdriver after the screw is firmly started, and not to use the sliding-cover split type for final tightening.1
Use a square blade with a wrench for a hard-turning screw
Heavy-duty common screwdrivers are made with square blades so that a wrench can be used on the blade. The manual says to use one with a properly fitting wrench for hard-to-turn screws, and not pliers.1
Use a cabinet screwdriver for deep holes
The cabinet screwdriver has a thin, round blade made to reach screws in deep, counterbored holes.1
A Phillips recess holds the screw on the driver
Phillips’s 1936 patent describes a recess and driver that join in a wedging fit, so a screw can first be secured to the end of a driver and presented to the work without dropping off. The patent says the screw also stays centered with respect to the driver throughout its advancement.1
Use a ratchet driver to avoid lifting the tip
With a ratchet screwdriver the action lever is set for installing or removing, and the screw is driven by pulling the handle back and forth, so the tip stays in the screw head between strokes.1

History

Earliest documented

late fifteenth century

Europe (the manuscript known as the Medieval Housebook)

In his history of the tool, Witold Rybczynski reports that the earliest screws he could find appear in a manuscript of the late 1400s known as the Medieval Housebook, in an illustration of a leg-iron fastened with slotted screws and a separate sketch of a screw. The earliest screwdriver blade he found was on a pair of sixteenth-century armormaker’s pincers in a British museum, one handle of which ends in a simple screwdriver.1 2

The screwdriver is younger than almost every other hand tool in this archive because it had nothing to do until the screw existed. Rybczynski found screws first in the late fifteenth century, in armor, firearms and timepieces, where they were cut by hand and were costly and unreliable. A tool to turn them did not need its own form: the earliest blade he found was the end of a sixteenth-century armormaker’s pincers. The tool’s names arrived later still, tournevis in French in 1723 and turnscrew in Scottish craft manuals of the later eighteenth century.

The tool took a settled form only after the screw was industrialized. The Canadian Encyclopedia dates the first industrial screw-making process to England in the 1760s and an automated method of cutting screws to Cullen Whipple of Providence in 1842. By the middle of the nineteenth century the turnscrew was a standard trade tool: a London-type turnscrew sits in a shipwright’s chest of 1845–1855 in the Science Museum Group collection, and a London maker was still cataloging the same pattern in 1926.

The slot was the weakness. A flat blade can slide out of a single slot, and the Canadian Encyclopedia records a run of patents for new heads between 1860 and 1890. Allan Cummings’s 1875 patent states the problem directly: his cavity head was meant to let a screw be driven with great rapidity and safety, without the driver slipping and damaging the slot or head. What defeated such designs was manufacture. UBC’s Dictionary of Canadianisms credits Robertson’s success to a tapered socket that allowed the heads to be formed cheaply by cold stamping.

The cruciform recess was designed for the power driver. Thompson’s 1933 patent, assigned to Phillips, emphasizes a single tool for many sizes and a recess that automatic machinery could punch. Phillips’s own 1936 patent frames the slotted screw’s failure as a problem of power-driven work, where a blade leaving the slot at speed endangers the operator and mutilates furniture and similar work. The Canadian Encyclopedia says the cruciform screw became the international standard during the Second World War, while Robertson’s square socket remained common mainly in Canada.

The result is a tool defined by its fastener. Each new drive required a matching tip, so the single turnscrew of the nineteenth century became a set of drivers and interchangeable bits, and much driving now happens in a powered tool. O*NET’s Tools Used table lists screwdrivers in 18 of the occupations mapped to this archive’s trades, and power drills, which commonly carry driver bits, in 21.

Timeline

late 1400s
Slotted screws appear in an illustration in the Medieval Housebook, the earliest screws Rybczynski found.1
1500s
A sixteenth-century armormaker’s pincers, one handle shaped as a screwdriver blade: the earliest screwdriver Rybczynski found.1
1723
The French word tournevis appears in print, as reported by Rybczynski.1
1760s
The first industrial process for making screws is developed in England.1
late 1700s
Scottish craft manuals of the period of the American Revolution name the tool the turnscrew, as reported by Rybczynski.1
1842
Cullen Whipple of Providence, Rhode Island, invents an automated method of cutting screws.1
1845–1855
A London-type turnscrew is part of a shipwright’s tool chest of this date, now in the Science Museum Group collection.1
1860–1890
Inventors file a run of patents for new screw heads to replace the slot; the Canadian Encyclopedia says all proved difficult to manufacture.1
1875
Allan Cummings of New York patents a wood screw with a cavity in the head in place of a slot, so that it may be driven without the driver slipping (US Patent 161,390).1
1907–1909
P. L. Robertson patents his square-socket screw in Canada; sources give 1907 and 1909 (see disputed).1 2
1926
Charles Nurse & Co. of London catalog a 10-inch London turnscrew (catalog no. 1498), later given to the Science Museum.1
1933
John P. Thompson of Portland, Oregon, is granted US Patent 1,908,080 for a screw with a tapered, pointed recess that lets one driver serve screws of various sizes and can be produced by automatic machinery; the patent is assigned to H. F. Phillips.1
1936
Henry F. Phillips is granted US Patent 2,046,837 for a screw and driver whose recess centers and holds the driver, written explicitly for power-driven operations.1

Where the sources disagree

When did P. L. Robertson patent the square-socket screw?

1907.1
The Canadian Encyclopedia
Invented in Milton, Ontario, in 1908 and patented in 1909.1
Dictionary of Canadianisms on Historical Principles (UBC)

Gaps in the record (4)

The Medieval Housebook evidence is known here through reviews of Rybczynski’s book; the manuscript itself and a museum record of the armormaker’s pincers have not yet been located and read.
Robertson’s Canadian patent number and text have not been located.
No standard drive-size table has yet been sourced for specs.
Care has no sourced entries yet.