Locking pliers

How it works

One handle carries the fixed jaw and an adjusting screw; the other handle works the movable jaw through a toggle lever. Turning the screw sets how far the jaws are apart when the handles are closed. Pressing the handles together then straightens the toggle, and the patent of Harold T. Jones (1950) describes it straightening out through a line drawn through the centers of three pins to develop an enormous pressure on the grip.

The lock comes from carrying the toggle just past that line. Jones writes that the length of the toggle’s foot lets the center of one pin just pass the center line to lock the grip, so that maximum hand pressure need not be applied all the time. Petersen’s 1924 patent describes the same condition as the operating handle swung outward and the handle beyond center, with the shank adjusted to force the jaw further onto the work.

To release, the user moves the toggle back across the center line. In Jones’s patent a releasing lever forces the handle slightly outward so that the toggle collapses under a coiled spring and the pressure of the work, and the jaws open. A coil spring connected to the movable jaw holds the jaws open when the grip is released; Petersen’s 1924 patent already used a retractable member for that purpose.

Anatomy

Fixed jaw and upper handle: A channeled handle carrying the stationary jaw; in Petersen’s 1924 design the end of the handle is closed and threaded to take the adjusting shank.
Adjusting screw: A knurled screw in the end of the handle; the Navy manual describes turning it to change the jaw opening.
Movable jaw: Pivoted to the handle and connected to the operating lever.
Toggle lever: A short link between the handles that straightens past center to lock.
Release lever: A small lever inside the lower handle that forces the toggle back across center; described in Jones’s 1950 patent and advertised by Petersen as “Easy Release” by 1957.
Opening spring: A coil spring that pulls the jaws apart when the toggle is released.

Variants

Straight-jaw: The original form, described by Petersen in its 1958 advertisement as the “Old Reliable” straight-jawed model.
Curved-jaw, with or without wire cutter: The 1958 advertisement lists 7 and 10 inch curved-jaw models with an involute jaw curve, knurled tips, a thin nose and an optional wire cutter.
Long-nose: Alloy Artifacts illustrates a No. 9LN locking long-nose pliers among its Petersen tools; no date or description for it was read.
C-clamp type: The 1958 advertisement lists an 11-inch C-clamp with “ice-tong” jaws, described as adjusting to the right opening before use and then locking to the work.
Sheet-metal tool: Wide, flat jaws for bending, forming, seaming and crimping sheet metal, listed in 1958 as the No. 8R; the Navy manual says clamp-type jaws are generally wide and smooth and used with sheet metal.
Welding clamp: U-shaped jaws that bring edges into alignment and lock; Christian Petersen’s 1956 patent describes a clamp for facilitating welding operations.

Specifications

Overall length · in: 7 and 10The standard and curved-jaw models in the 1958 advertisement were made in 7 and 10 inch lengths.
Weight · oz: The 1958 advertisement gives 13 oz for the 7-inch and 20 oz for the 10-inch models.

Made to

ASME B107.500
ISO 5743

Safety and care

Safety

The Navy’s 1971 manual cautions that the teeth in locking-pliers jaws tend to damage the object clamped, and says they should not be used on nuts, bolts, tube fittings or other objects that must be reused.

Tips

Set the opening with the screw, then lock with the lever
The Navy manual says a screw in one handle adjusts the jaw opening and that pulling the lever toward the handle clamps and locks the pliers. Setting the screw before closing is how the grip is tuned to the work.1 2
The release lever opens the jaws with one finger
Jones’s patent places a release lever inside the lower handle so that the grip can be released instantly by a finger of the hand holding the pliers. Petersen advertised this as Easy Release.1 2
Tighten the end screw for plain plier action
Petersen’s 1958 advertisement says the pliers adjust to plier action, and for its sheet-metal tool says that when the locked grip is not needed the end screw is tightened for non-locking plier action.1
Curved jaws take hold of a nut on four points
Petersen’s curved-jaw model, says its 1958 advertisement, has an involute jaw curve that gives tooth contact on four points of a nut and more on round work.1
Wide flat jaws suit sheet metal
The Navy manual says the wide, smooth clamp-type jaws are used primarily with sheet metal, and Petersen listed a sheet-metal tool for bending, forming and crimping.1 2
A welding clamp frees both hands
Petersen’s 1958 advertisement describes the U-shaped welding clamp as aligning the edges and holding them locked, freeing both hands for the work.1 2

History

Earliest documented

1921

De Witt, Nebraska, United States

William Petersen of De Witt, Nebraska, was granted US Patent 1,392,443 on 4 October 1921 for a wrench whose jaws have a vise gripping action, closed by a threaded actuator. The locking toggle appears in his patent 1,489,458 of 8 April 1924. Whether earlier toggle-locked pliers or wrenches existed has not been established; the later Jones patent lists earlier patents of record that have not been read.1 2 3

Locking pliers were invented for a shop where neither of two tools quite served. According to Wessels Living History Farm, which tells the story from the company’s side, William Petersen found that pliers could not be locked and that a vise was hard to set up, and combined the two. His 1921 patent shows the first half of that idea: a wrench whose jaws close with a vise-like grip, driven by a screw in the handle. The patent does not yet lock; the 1924 patent adds the articulated lever that is swung past center.

The principle of the lock is the toggle. In the 1924 patent and in Jones’s 1950 patent the link between the handles is carried just past the straight line through its pivots, so that the closing force is multiplied and then held by the geometry of the linkage instead of by the hand. Jones’s patent shows how the lock is undone: a release lever pushes the toggle back across the center line and a spring then opens the jaws. Petersen’s 1924 patent already notes that the tool can be used as pliers, as a ratchet wrench and as a pipe wrench.

Wartime demand and patent expiry shaped the market. Alloy Artifacts records a government contract in 1941, the year the original patent expired, followed by competing locking pliers sold by Sears, H. R. Basford and Seymour Smith; Wessels says defense industries used thousands of the tools. After the war, Petersen extended the design into clamps and a welding clamp, and by 1957 added the release lever from Jones’s patent. Alloy Artifacts notes that the Jones patent was apparently licensed, since no assignment is recorded.

The brand became the common name. The Navy’s 1971 training manual calls the tool “wrench (Vise-Grip) pliers” and describes it as a clamp, a speed wrench, a portable vise and more, with an advantage over other pliers that it can be clamped on an object and will stay. O*NET’s Tools Used table lists locking pliers for all 8 of the occupations that this archive maps to the tool.

Timeline

1921
US Patent 1,392,443 (William Petersen, De Witt, Nebraska): a wrench in which the jaws have a vise gripping action, with a screw actuator in the handle.1
1922
First use date of the “Vise Grip” trademark, registered in 1923 to the Sire & Petersen Wrench Company, according to Alloy Artifacts.1
1924
US Patent 1,489,458: a wrench usable as pliers, as a ratchet wrench and as a pipe wrench, with an articulated lever that is swung beyond center to grip with the force of a vise. One half of the patent is assigned to a partner at De Witt.1
1932
A Hardware Age notice of 25 February 1932 names the Petersen Manufacturing Company of De Witt, Nebraska, as maker of the Vise-Grip wrench.1
1934
Wessels Living History Farm dates the formation of the Petersen Manufacturing Company to 1934 (see disputed).1
1938
Petersen Manufacturing opens its first manufacturing plant in a former drugstore in De Witt, with a staff of 37, according to Wessels Living History Farm.1
1941
The company wins a government contract for the war effort and Petersen’s original patent expires; competitors then introduce similar locking pliers.1 2
1942
US Patent 2,280,005 (Petersen): a stub lever and fulcrum bar arrangement, held in place by a slot so that it cannot fall out of the handle, used by the company after the first patent expired.1 2
1950
Harold T. Jones receives US Patent 2,514,130 for a toggle release lever inside the handle of a locking wrench and pliers, filed 1944.1
1956
Christian Petersen’s US Patent 2,731,932 for a welding clamp built on the locking-pliers mechanism, assigned to Petersen Mfg. Co.1
1957
Petersen advertises Vise-Grip pliers with “Easy Release”; Alloy Artifacts finds a May 1957 Popular Science advertisement to be the earliest known public reference.1 2
1958
Petersen’s trade advertisement lists straight-jaw and curved-jaw models, a C-clamp, a sheet-metal tool and a welding clamp, all with the new release.1
1985
The Petersen family forms American Tool Companies, which acquires Petersen Manufacturing; American Tool later acquires the Irwin Tool Company (1993) and is acquired by Newell in 2002.1
2008
Wessels Living History Farm records the closing of the original De Witt plant when the parent company moved production to China.1

Where the sources disagree

When was the Petersen Manufacturing Company formed, and under what name did the firm first operate?

The firm was founded around 1923 as the Sire & Petersen Wrench Company, and by 1932 had changed its name to the Petersen Manufacturing Company, according to a Hardware Age notice of that year.1
Alloy Artifacts
The Petersen Manufacturing Company was formed in 1934, and its first official plant opened in 1938.1
Wessels Living History Farm

Gaps in the record (8)

Whether any toggle-locked pliers or wrench existed before Petersen’s 1924 patent has not been established; the earlier patents cited on the face of Jones’s patent have not been read.
The Petersen patents were read for their mechanism; their assignments (Sire & Petersen) rest on Alloy Artifacts, since the 1924 patent heading is poorly scanned.
Both company histories (Alloy Artifacts, Wessels) are secondary; no Nebraska archive or Petersen company record has been read.
Other names for the tool (for example British trade names) have not been sourced.
The date of the 9LN long-nose model is not established.
The standards slugs are unverified guesses; no independent test or failure data has been sourced, so buying is null.
Irwin’s current Vise-Grip instructions could not be read, so no current manufacturer instructions are cited.
Care has no sourced entries.