Wire stripper

How it works

The wire is placed between the blades at the hole or notch that matches the conductor size. Closing the handles brings the blades down on the insulation to cut it, and a pull along the wire strips the slug of insulation from the end. In the squeeze-action tools of the mid-twentieth century the same motion first grips the wire between serrated jaws, then cuts, then draws the cutting blades away along the wire so that the slug is pulled off.

The cutting hole is sized to the conductor. Ideal Industries describes the blades of its Custom Stripmaster as having an outer counterbore sized to the insulation, which compresses it slightly, and an inner hole that cuts the insulation without contacting the wire.

Anatomy

Handles: Two levers, with plastic grips on later models, joined at a pivot; a coil spring returns them.
Cutting blades: A pair of blades with a graduated series of holes or notches sized to wire gauges.
Gripping jaws: Serrated jaws that hold the wire while the blades cut and withdraw; Hindenburg’s 1959 patent describes serrations shaped to grip a fragile coating without nicking it.
Wire stop: An adjustable stop that sets the length stripped; Ideal describes a transparent “see-thru” wire stop.
Latch: A short-stop latch that limits the stroke so that the slug is loosened but not removed.

Variants

Notched plier-type stripper: Two handles with blades that overlap and bear triangular or round notches; Bettinger’s 1894 patent is an early example, for linemen stripping fibrous covering.
Squeeze-action precision stripper: Levers with gripping jaws and stripping blades that grip, cut and pull in one stroke; Ideal’s 1962 catalog lists models for wire sizes 8 to 30.
Thermal stripper: Melts and removes insulation without cutting the wire; Ideal’s 1962 catalog lists a plier-type pincer tool with a power unit for Teflon and similar insulation.
Self-adjusting and automatic strippers: O*NET lists self-adjusting and automatic insulation strippers among the tools used by the trades; no history of them has been sourced here.
Cable jacket and sheath strippers: Listed by O*NET as separate tools; not described here.

Specifications

Wire sizes covered · AWG: 10 to 30 (Custom Stripmaster); 8 to 30 across Ideal’s 1962 modelsThe American Wire Gage sizes of solid round conductors are standardized in ASTM B258.
Maximum strip length · in: 7/8 with the short-stop latch disengagedIdeal’s 1962 catalog description of its latch.
Weight · oz: about 10Weight given for one Ideal squeeze-action model in the 1962 catalog.
Blade hole tolerance · in: Not sourced.

Made to

ASTM B258
IEC 60900

Safety and care

Safety

OSHA treats conductors that have been deenergized but not locked out or tagged as energized and applies its rules for work on or near energized parts to them (29 CFR 1910.333(b)(1)), so work on them falls under the rules for energized parts unless they are locked out or tagged.

Tips

Choose the hole that matches the conductor
Ideal says its matched sets of blades are precision drilled to exact wire sizes so that the insulation is stripped without nicks or scrapes to the conductor, and its models are sold by gauge range, for example 10 to 30 AWG for the Custom Stripmaster.1 2
Use the stop for repeatable lengths
An adjustable wire stop set against the end of the wire strips each conductor to the same length. Ideal describes a transparent wire stop on its Stripmaster models, which assures uniform lengths.1 2
Set the short-stop latch to loosen the insulation without removing it
The latch on Ideal’s 1962 models limits the stroke to 5/32 inch and can be disengaged for a full 7/8 inch strip. Hindenburg’s patent describes the partial stroke as one that only partially removes the slug, and gives the purpose as preventing the stripped ends of the wires from being frayed or damaged.1 2
Let the jaws stay open after the strip
Ideal calls its automatic feature, which holds the jaws open after stripping, a way to remove the wire without crushing it.1
Use a stripper made for the insulation
Ideal’s 1962 catalog lists a general-purpose model for plastic, fiberglass and other hard-to-strip insulation, a precision model for all thermoplastic insulation including Teflon, and thermal tools for critical stripping where no wire damage is permissible.1 2

History

Earliest documented

5 June 1894 (earliest patent located)

Hamilton, Ohio, United States

John J. Bettinger of Hamilton, Ohio, patented a wire stripper for electric linemen to strip the fibrous covering from insulated wires: two spring-bowed handles carrying overlapping blades with hardened triangular notches, which were squeezed on the wire, twisted to cut the covering and pulled endwise to strip it.1

The wire stripper took over from the knife. Holt’s 1952 patent describes the earlier practice of cutting a wire to an estimated length and then stripping its ends, and says that where existing strippers could not be used in the small spaces of electrical and electronic equipment, it was necessary to strip the insulation with a small knife or to detach the wire from the device and reattach it. Bettinger’s 1894 patent shows the tool in the lineman’s kit: two handles joined by a spring bow, with notched blades that cut the fibrous covering as they were squeezed and twisted, and a pull to strip it.

The tool’s form was settled by solving one problem after another. Wood’s 1915 patent addressed the lack of any means of holding the wire against the pull of the stripper, which required the other hand. Lund’s 1932 patent addressed tools that handled only short lengths or demanded too much force, and gave replaceable knives with openings sized to the wire. Axelsen’s 1948 application, assigned to Ideal Industries of Sycamore, Illinois, combined jaws that grip the wire with blades that cut and slide to strip in one operation, with a latch that holds the parts for the return stroke.

Insulation materials changed the blades and jaws. Hindenburg’s 1956 application states that coatings such as Teflon and Fiberglas are tough in tension but slippery, easy to nick but hard to cut, and describes jaws with serrations shaped to grip them without nicking and a latch that limits the stroke. Ideal’s 1962 catalog shows the result: precision “concentric hole” blades drilled on watchmaker’s equipment, models for gauges 8 to 30, and heat-based tools that melt the insulation for critical work.

The tool now exists in many forms for a trade that uses it widely. O*NET’s Tools Used table lists wire strippers for all 6 of the occupations mapped to this tool in the archive’s crosswalk and also lists self-adjusting, automatic, end, universal and cable-jacket strippers. The standard that matters to the user of any of them is the gauge system for the wire; ASTM B258 gives the nominal diameters and areas of AWG sizes of solid round conductors.

Much of the later history is told by the maker. Ideal’s history page says the company patented the first thread-on wire connector in the United States in 1929 and trademarked Wire-Nut in 1960, and that its strippers were requested for the 1969 moon landing module; these are the company’s own statements. The Custom Stripmaster literature says its blades meet military stripping specifications, which is also a manufacturer’s claim.

Timeline

1894
Bettinger’s US Patent 520,818 describes a plier-type stripper with notched blades for linemen.1
1915
Stuart G. Wood of Brooklyn patents a stripping device (US 1,151,319, issued 24 August) that holds the wire against the pull of the stripper, so that the user need not hold the wire with the other hand, which was a problem in confined spaces such as between building walls.1
1916
Wood patents a second device (US 1,196,322, issued 29 August) with a wire clamp and several stripping devices acting at different points along the wire.1
1916
J. Walter Becker founds the IDEAL Commutator Dresser Company of Chicago, which became IDEAL Industries; the company moved to Sycamore, Illinois in 1924.1
1932
Isak Lund’s US Patent 1,857,731 (filed 1931) describes gripping handles carrying replaceable stripping knives with central openings sized to the wire, which strip insulation at any length or from a loop in the wire and scrape the wire bright.1
1950
Howard C. Axelsen of Sycamore, Illinois, assignor to Ideal Industries, receives US Patent 2,523,936 (filed 1948) for a hand stripper with gripping and cutting elements on pivoted frame members, latch and return spring.1
1952
William J. Holt, Jr., of Garland, Texas, receives US Patent 2,601,797 (filed 1950) for a stripper that works inside small spaces in electrical and electronic equipment.1
1959
Eugene D. Hindenburg of De Kalb, Illinois, assignor to Ideal Industries, receives US Patent 2,889,728 (filed 1956) for an auxiliary latch on a stripper of the Axelsen type, for stripping tough, slippery coatings such as Teflon and fiberglass.1
1962
Ideal’s 26th Edition catalog lists squeeze-action strippers for wire sizes 8 to 30, with the Hindenburg patent number on the Teflon models, and thermal strippers.1
1969
Ideal says its wire strippers were specifically requested for components of the 1969 moon landing module because of their quality and precision (company statement).1

Gaps in the record (6)

The origin of the Stripmaster name and the date of the first Stripmaster have not been located. Ideal’s 1962 catalog lists the model numbers (45-170 and following) that appear in a later parts list titled Stripmaster, but neither names the date of introduction.
The first self-adjusting stripper, its inventor and date have not been found.
Earlier wire-stripping patents than Bettinger’s 1894 patent may exist and have not been searched for.
The year of the Custom Stripmaster literature and the military stripping specification it cites have not been identified.
No independent test data on stripping damage, durability or blade life has been located, so no quality judgment is made.
Care has no sourced entries yet.