Combination wrench

How it works

Each head is forged to one fastener size. The box end encloses the fastener, usually with a 12-point opening, and the open end is a U-shaped jaw. Alloy Artifacts defines the combination wrench as a style with an open end and a box end of the same size.

The box end applies force to the flat sides of the fastener head. TEKTON states that its 12-point box end is designed to contact the sides of the head and not the corners, which prevents rounding; Gray Tools adds that a 12-point head offers twice the alignment angles of a 6-point head and needs only a 30 degree swing to reposition.

The heads are tilted at 15 degrees to the handle on common modern wrenches, for clearance for the fingers and to make the wrench easier to flip over between strokes.

Anatomy

Open-end head: A U-shaped jaw angled at 15 degrees on TEKTON’s wrenches so the wrench can be flipped over with each rotation.
Box-end head: A closed ring, typically 12-point, offset 15 degrees from the handle on the TEKTON and Gray Tools examples.
Shank (handle): A forged bar between the heads. Alloy Artifacts notes oval-shank and depressed-panel styles in Billings’s wrenches of the late 1930s.

Variants

Offset 15-degree combination wrench: The common modern pattern: box end offset and open end angled at 15 degrees.
Straight-head combination wrench: Heads in line with the handle, as on the Plomb wrenches of 1933 described by Alloy Artifacts.
Open-end wrench (engineer’s wrench): Open ends only, at two sizes; Billings lists double-open “Engineer’s” wrenches among its early alloy-steel line.
Box-end (ring) wrench: Box heads only, single-offset or double-offset; Plomb offered 12-point box wrenches from 1926.
Flare-nut wrench: A box wrench with a slot cut through the ring; covered by the same ASME standard as flat wrenches (B107.100).

Specifications

Size range (inch series) · in: 5/16 to 1-1/2 (Gray Tools, 12-point 15-degree offset set)The range is one maker’s catalog; sets are sold by fastener size, inch or millimeter.
Offset angle · degrees: 15TEKTON and Gray Tools both state 15 degrees for the box end.
Points in box end · count: 1212-point is common; 6-point box wrenches are also made.

Made to

ASME B107.100
ISO 691
ISO 1711-1

Safety and care

Safety

OSHA states that wrenches must not be used when the jaws are sprung to the point that slippage occurs.

Tips

Flip the wrench over between strokes
TEKTON explains that the open end is angled 15 degrees so that, in a tight space where the swing arc is short, the wrench can be turned over with each rotation and engage the fastener twice as often.1
A 12-point box end needs only a short swing to reseat
Gray Tools states that a 12-point head has twice the alignment angles of a 6-point head, engaging the fastener sooner and needing only a 30 degree swing to reposition in tight spaces.1
The 15-degree offset is for clearance
TEKTON says the offset of the box end creates clearance for the fingers and makes it easier to reach around obstructions; Gray Tools describes it as clearance for the knuckles.1 2
The box end drives the flats, not the corners
TEKTON says its 12-point box end contacts the sides of the fastener head and not the corners, and gives this as the reason it prevents rounding of the fastener.1

History

Earliest documented

25 April 1933 (documentary, for the combination form)

Los Angeles, California (Plomb Tool Company)

Alloy Artifacts reports that Plomb announced its new combination wrench, an open end and a box end of the same size, in the April 25, 1933 issue of its newsletter Sparks from the Anvil, in four sizes, and that Plomb is generally credited with the first modern combination wrench. Open-ended fixed spanners are far older; the Science Museum Group holds a brass hexagonal-and-circular spanner made by George Adams of London in 1760, and the Victoria and Albert Museum holds a wheel-lock spanner of the sixteenth century from Italy.1 2 3

The combination wrench is the product of three older things: the fixed spanner, the box wrench and alloy steel. The Science Museum Group holds a brass spanner made in 1760 by George Adams of London and spanners by J. Whitworth and Co., and the V&A holds a sixteenth-century Italian wheel-lock spanner, a steel bar with a spanning head at one end and a screwdriver at the other, which was used to wind the lock of a firearm. The adjustable wrench, discussed in its own entry, served for odd sizes.

The box end needed a stronger steel than the open spanner. Alloy Artifacts, writing about Plomb, calls the 12-point box wrench a new class of tool made possible by alloy steel, and records that Plomb offered single-ended 12-point box wrenches by 1926 and double-offset ones by 1928. Billings’s 1930 contract to make alloy-steel wrenches for Craftsman moved from open-end wrenches to box-end wrenches by 1933, which shows the trade making the same change.

Joining the two heads was the last step. Alloy Artifacts says Plomb is generally credited with the first modern combination wrench, announced in April 1933 in four sizes, and that Plomb itself called the new tools “Combination” wrenches, a name that mattered because other makers gave the tool odd names such as TuType, Multitype and Half & Half. Billings listed Vitalloy combination wrenches in its 1938 catalog. No patent for the combination form has been located, so the credit rests on this trade history and on dated catalogs and newsletters.

The shape on the modern wrench was set by the demands of tight spaces. TEKTON’s description is specific: the open end is angled 15 degrees so the wrench can be flipped with each rotation, the 12-point box end has radiused contact to avoid rounding, and the box end is offset 15 degrees for finger clearance. Gray Tools sells a 12-point wrench with a 15 degree offset described as providing knuckle clearance. The Hand Tools Institute lists a 2023 edition of ASME B107.100 among the B107 hand-tool standards.

The combination wrench is widely listed: O*NET’s Tools Used table gives specialty wrenches, the commodity class under which it falls, in 6 of the 24 occupations mapped to this archive’s trades.

Timeline

16th century
A wheel-lock spanner of steel, with a spanning head at one end and a screwdriver at the other, is made in Italy; it is the V&A’s example of the tool that gave the spanner its name in English.1
1760
George Adams of Fleet Street, London, makes a brass spanner, now in the Science Museum Group collection.1
1926
Plomb offers an A-series of single-ended 12-point box wrenches, one of the earliest such tools along with P&C, according to Alloy Artifacts, and an important new class of tool made possible by alloy steel.1
1928
Plomb offers an AD-series of double-offset box wrenches in six sizes from 7/16 by 1/2 to 15/16 by 1 inch.1
1930
Billings and Spencer takes a contract to produce alloy-steel wrenches for the Craftsman brand of Sears Roebuck, at first open-end and tappet wrenches.1
1933
Plomb announces its combination wrench (25 April); Billings extends its Craftsman production to box-end wrenches.1 2
1938
Billings’s 41st edition catalog lists Vitalloy combination wrenches in a 5xxx series from 7/16 to 7/8, according to Alloy Artifacts.1
1948
Plomb has to change its brand name to Proto after a trademark problem, according to Alloy Artifacts.1

Gaps in the record (7)

No patent for the combination wrench has been located; the 1933 Plomb newsletter is known here only through Alloy Artifacts’ account, and the newsletter itself has not been read.
The 12-point box wrench is said to have been offered by P&C as early as Plomb; P&C’s date has not been sourced.
No patent or catalog has been found for the first box wrench of any kind, or for the offset angle of 15 degrees.
ASME B107.100 has not been read, so jaw tolerances, wall thickness and proof torque are not given.
Care has no sourced entries.
A retailer’s claim that Loring Coes invented the combination wrench in 1903 was seen in a search result but not fetched or confirmed; it likely refers to an adjustable form (Coes’s 1841 patent is covered in the adjustable wrench entry) and is not used.
No independent test data has been found, so buying is null.