Adjustable wrench

How it works

The fixed jaw is forged with the handle. The movable jaw slides in a slot or on a bar, and a screw sets the gap between the two faces to the width of the nut. On the modern pattern the screw is a worm, turned by the thumb, whose thread engages a toothed rack on the movable jaw. Karl Peterson’s 1915 patent for the Crescent wrench describes exactly this: an extension of the movable jaw with a rack on its underside, sliding in a slot in the head and driven by a worm.

The user turns the nut by pulling on the handle. Because the jaws are separate parts, the tool is less rigid than a solid wrench, and the movable jaw and its guide carry the load. Peterson’s patent states that the fixed jaw is weakest at its angle and most likely to break there, and adds braces at that point; it also seeks a positive adjustment that is not changed when the wrench is dropped.

Setting the jaws at an angle to the handle gives a longer sweep in a confined space. Edward J. Worcester’s 1857 patent describes a wrench with its jaws inclined to the shank, which he says is often more convenient than the common form with jaws at right angles, and his rack therefore moves across the handle rather than along it.

Anatomy

Handle: Forged in one piece with the fixed jaw and head on the modern pattern.
Fixed jaw: Part of the head; Peterson’s 1915 patent braces it where it meets the head, which it identifies as the weakest point.
Movable jaw: Slides in a slot in the head; on the Crescent pattern its extension carries a rack on the underside.
Worm (adjusting screw): A short threaded wheel turned by the thumb that drives the rack; in Peterson’s patent it is held under spring tension so it does not run freely.
Rack: Teeth cut on the movable jaw that mesh with the worm.
Worm pin: The axle on which the worm turns, held in the head.

Variants

Wedge- or peg-adjusted spanner: An early form in which the jaw was set with a wedge or a fixing peg. The Old Lawnmower Club describes wedge adjustment as the method before Budding and Clyburn; the Science Museum Group holds a cast-iron Great Eastern Railway spanner with a sliding head and fixing peg.
Clyburn pattern: A worm set in a gap in the body between the fixed and moving jaw, according to the Old Lawnmower Club; Grace’s Guide says the design was made mainly by Birmingham firms and listed in catalogs until about 1964. The Science Museum Group holds three Clyburn wrenches, the largest 375 mm long.
Budding pattern: A worm along the back edge of the spanner, turned by finger or thumb; the Old Lawnmower Club says it was also called an “English key.”
Monkey wrench (bar-and-sliding-jaw): Jaws at right angles to a straight shank, the lower jaw moving along the shank. Coes’s 1841 patent put the adjusting screw beside the shank so it could be turned by the thumb.
Angled-head adjustable (Johansson / Crescent pattern): Jaws inclined to the handle, movable jaw driven by a worm and rack. Tekniska museet credits Johansson’s 1892 design with a single movable jaw set by an adjusting screw; Peterson’s 1915 patent covers the Crescent version.
Double-ended adjustable: Adjustable heads at both ends; the Science Museum Group holds an example (object 1976-84).

Specifications

Nominal length · in or mm: Adjustable wrenches are sold by overall length; the three Clyburn wrenches in the Science Museum Group measure 375, 290 and 270 mm. No standard size table has yet been sourced.
Jaw capacity · in or mm: Maximum opening of the jaws; not yet sourced from a standard.
Jaw angle to handle · degrees: Worcester (1857) and Peterson (1915) both incline the jaws to the handle; neither patent states an angle.

Made to

ASME B107.100
ISO 6787
DIN 3117

Safety and care

Safety

Peterson’s 1915 patent identifies the angle of the fixed jaw as the point where the wrench is weakest and most likely to break.
Harris’s 1885 patent and Coes’s 1841 patent both describe earlier wrenches whose jaws or handles worked loose or broke under strain; Coes says his parts support each other better under heavy load and are less liable to break than the ordinary wrench.

Tips

Put the pulling force on the fixed jaw
The manual states that the wrench is placed so the force used to turn it is applied to the stationary jaw side, and warns never to turn adjustable wrenches with the pulling force on the adjustable jaw.1
Close the jaws snugly on the nut
The knurled adjusting nut is tightened until the wrench fits the nut as tightly as possible. The manual says that a wrench which does not fit tightly will slip and round the corners of the nut.1
Pull the wrench
The manual says to pull on a wrench when possible, to protect the knuckles if it slips.1
Apply penetrating oil to a stuck nut
For rusted nuts and bolts that resist turning the manual calls for penetrating oil, with time allowed for it to penetrate before the wrench is turned. The manual also advises against extending the handle to gain leverage, because increased leverage may damage the wrench or the work.1

History

Earliest documented

1809 (documentary)

Portsmouth, England

Peter Jensen Brown reports, citing the Repertory of Arts, Manufactures, and Agriculture for 1809, that William Barlow of His Majesty’s Dock-Yard, Portsmouth, received a premium of five guineas for a wrench adjusted by a nut and screw to fit nuts of various sizes. The original volume has not been read here. By 1841 Loring Coes’s US patent could compare his design with “the ordinary wrench with the screw cut or formed on the shank,” showing that screw-adjusted wrenches were already in common use.1 2

The adjustable wrench answered the problem of nuts that came in no fixed sizes. Barlow’s 1809 description, as quoted by Peter Jensen Brown, complains that engine nuts were often injured for want of an instrument that would fit a variety of sizes and hold as firmly as a solid wrench. Digital Stroud makes the same point about the English spanners of the 1840s, which made it easier to hold non-standard hand-forged bolts. While every machine shop cut its own threads and forged its own nuts, one tool that could be set to any of them had an obvious use.

The early forms were set by wedges, pegs and long screws. The Old Lawnmower Club describes the spanners before Budding and Clyburn as adjusted by a small wedge between the body and the moving jaw, which made a precise setting difficult and let the jaw shift if the wedge came loose. In America the screw ran up the shank; Coes’s 1841 patent moved it to the side, where the thumb of the hand holding the wrench could turn it, and argued that this made the wrench stronger. By 1840, the year before Coes’s patent, the North Union Railway in England already required every engine-man to carry a large and a small monkey wrench.

The worm was the decisive change. Budding’s registered design of 1843 put a worm along the back of the spanner, and Clyburn’s put it in a gap between the jaws; the Old Lawnmower Club says both removed the limitations of the wedge. Worcester’s American patent of 1857 combined a rack and screw with jaws inclined to the handle. The angled head with a single movable jaw driven by a worm, which Tekniska museet credits to Johansson in 1892 and which Peterson patented for Crescent in 1915, combines these elements and is the form in general use today.

Manufacture decided which design spread. Tekniska museet reports that Johansson’s firm made 300 adjustable spanners in 1892 and 4,000 a year a decade later, sold worldwide by B. A. Hjorth, and that Bahco has since made 100 million. Alloy Artifacts records that Crescent’s hardest problem was cutting the slot for the sliding jaw, for which it built a special slotting machine, and that its 1909 wrench used an alloy-steel jaw. Crescent itself says that an adjustable wrench and slip-joint pliers were supplied with every Ford Model T, and Alloy Artifacts notes that all makes of the style came to be called “crescent” wrenches.

The adjustable wrench did not displace the fixed wrench so much as cover the jobs where the size was unknown or the kit had to be small. Its separate jaw makes it less rigid than a solid wrench, a weakness Peterson’s own patent addresses with braces at the fixed jaw. O*NET’s Tools Used table lists adjustable wrenches in 13 of the 24 occupations mapped to this archive’s trades.

Timeline

1809
William Barlow of the Portsmouth dockyard receives a premium for a nut-and-screw adjustable wrench, according to Peter Jensen Brown’s reading of the Repertory of Arts.1
1826
A “monkey wrench” is reported stolen at Chester, England, the earliest use of the term found by Peter Jensen Brown.1
1840
North Union Railway rules require every engine-man to carry one large and one small monkey wrench, the earliest date-certain references cited by Language Log.1 2
1841
Loring Coes of Springfield, Massachusetts, patents a screw wrench whose adjusting screw sits beside the shank and is turned by the thumb (US Patent 2,054).1
1843
Edwin Budding registers a screw-adjustable spanner design (No. 7213) on 19 May; Richard Clyburn of Uley Iron Works is recorded the same year with a patent or registration for a screw-wrench or spanner.1 2 3
1844
A show report says Lord Ducie had so many orders for his improved screw spanners that he declined more, and that they were really invented by Richard Clyburn.1
1857
Edward J. Worcester patents a wrench with jaws inclined to the shank and a rack and screw moving the jaw across the handle (US Patent 17,531).1
1862–1864
Schwartzkopf’s universal spanner is patented and made in the UK by the Argus Works, Sheffield, according to the Science Museum Group.1
1885
Enoch Harris of Quincy, Illinois, patents a wrench whose handle can be set and locked at any angle and whose jaw is moved by a feed-screw (US Patent 326,868).1
1891–1892
Johan Petter Johansson of Enköping patents a spanner with two movable jaws in 1891 and an improved one with a single movable jaw in 1892; 300 are made in 1892, according to Tekniska museet.1 2
1907
Karl Peterson founds the Crescent Tool Company in Jamestown, New York.1 2 3
1909
A notice in American Exporter describes the new Crescent adjustable wrench, with a high-carbon steel handle and a movable jaw of special alloy steel, according to Alloy Artifacts.1
1915
Karl Peterson is granted US Patent 1,133,236 for the Crescent worm-and-rack adjustable wrench, assigned to Crescent Tool Company.1
1929
The tool dealer Buck and Hickman gives the Science Museum a set of adjustable wrenches and spanners, including three Clyburn wrenches and a King Dick No. 2.1 2

Where the sources disagree

Who invented the screw-adjusted spanner in England?

Edwin Beard Budding invented the screw adjustment, made at the Phoenix Ironworks, Thrupp.1 2
Digital Stroud; Grace’s Guide (Budding entry, registration of 1843)
Budding registered a design on 19 May 1843; Richard Clyburn came up with a similar design shortly afterward.1
The Old Lawnmower Club
Clyburn is credited with inventing the first adjustable spanner in 1842 and registering it in 1843; an 1844 show report says the spanners shown on Lord Ducie’s stand were really Clyburn’s invention.1
Grace’s Guide (Clyburn entry)
The first adjustable spanner was invented by the Englishman Joseph Stubs, fifty years before Johansson.1
Tekniska museet
William Barlow of the Portsmouth dockyard may have invented the first screw wrench, in 1809.1
Peter Jensen Brown

Was the monkey wrench named after a man called Charles Moncky?

Accounts from the early 1880s attribute the wrench to Charles Moncky, said to have sold his invention and to be living in Brooklyn.1 2
As summarized by Language Log and Peter Jensen Brown
The term was in print by 1840 (railway rules) and 1826 (a theft report in Chester), before a Brooklyn toolmaker named Charles Monk could have coined it; the story is folk etymology.1 2
Peter Jensen Brown; Language Log

When did Johansson patent his adjustable spanner?

A two-movable-jaw spanner in 1891, improved to a single movable jaw in 1892.1
Tekniska museet
Patent No. 4066 of 1892, as reproduced in the 1926 BAHCO catalog.1
Alloy Artifacts

Where did the Crescent wrench come from, and when was it introduced?

Introduced in 1907; engineering drawings date to 1908; the first adjustable wrench produced in America.1
Crescent (Apex Tool Group)
Swedish immigrant Gunnard Oberg brought the prototype to Jamestown and sold it to Karl Peterson for $500.1
Fenton History Center
Company folklore says a visitor from Sweden described a wrench he had seen there; the design likely drew on Johansson’s 1892 patent and owes a debt to Worcester’s 1857 patent; the wrench was announced in 1909.1
Alloy Artifacts
Adjustable wrenches had been patented and made in the United States since at least 1841.1 2
US Patents 2,054 (Coes, 1841) and 17,531 (Worcester, 1857)

When was Johansson’s Enköping workshop founded?

1886.1
Alloy Artifacts
He bought a waterfall outside Enköping in 1887 to power his newly started company.1
Tekniska museet

Gaps in the record (9)

Barlow’s 1809 wrench is known here only through Peter Jensen Brown’s quotation of the Repertory of Arts; the original volume has not been read.
The texts of the 1843 Budding registration (No. 7213) and the Clyburn patent or registration have not been located; whether Clyburn’s was a patent or a registered design is unclear in the sources.
No source for Joseph Stubs’s adjustable spanner, named by Tekniska museet, has been found.
Johansson’s Swedish patents have not been read in the original; Bahco’s own history pages refused access from this machine.
The Science Museum Group records for Clyburn wrenches give no dates of manufacture.
Crescent’s statement about the Ford Model T kit sits under a 1927 heading in its timeline; the years it covers are not stated.
No standard size or jaw-capacity table has yet been sourced for specs.
Care has no sourced entries yet.
No independent test data has been found, so buying is null.