Utility knife

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"Boxcutter" and "box cutter" redirect here. For the electronic music artist, see Boxcutter (musician).

a Stanley 99E fully retracted

A utility knife (also called a box cutter, a razor blade knife, a carpet knife, or a stationery knife) is a common tool used in various trades and crafts for a variety of purposes.

Such a knife generally consists of a simple and cheap holder, typically flat, approximately one inch (25 mm) wide and three to four inches (75 to 100 mm) long, and typically made of either metal or plastic. Some use standard razor blades, others specialised double-ended blades as in the illustration. The user can manually adjust how far the blade extends from the handle, so that for example the knife can be used to cut the tape sealing a package without damaging the contents of the package. When the blade becomes dull, it can be quickly reversed or switched for a new one. Spare blades are often stored in the hollow knife handle, and can be accessed by removing a screw and opening the handle. This type of tool is known in British English, Australian English, New Zealand English and Dutch as a Stanley knife, a genericized trademark named after one of the manufacturers to create this kind of implement.

[1]. Fixed blade versions are widely used for handcrafts. The blades for a utility knife come in both double and single ended versions, and are interchangeable with many but not all of the later copies. Specialised blades also exist for cutting string, linoleum and other purposes. Spare or used blades may be stored in the handle.

Segmented blade type

Disassembled, blade partly extended

Another style is a snap-off utility knife that contains a long, segmented blade which slides out from it. As the endmost edge becomes dull, it can be snapped off from the rest of the blade, exposing the next section which is sharp and ready for use and increases safety. When all the individual segments are used, it is thrown away or a replacement blade is inserted. This design was introduced by OLFA® Corporation in 1956 as the world's first snap-off blade and was inspired from analyzing the sharp cutting edge produced when glass is broken and how pieces of a chocolate bar break into segments. The demand for the snap-off blade has escalated worldwide.

A style that is often used for the cutting of boxes consists of a simple sleeve around a rectangular handle into which single-edge razor blades can be inserted. The sleeve slides up and down on the handle, holding the blade in place during use and covering the blade when not in use.

Tool types

[edit] Spreader-Cutters

A combination spreader-cutter with a built-in, manually operated pump

Detail of a combi-tool's blades.

In operation, the tips of the spreader-cutter's blades are wedged into a seam or gap — for example, around a vehicle door — and the device engaged. The hydraulic pump, attached to the tool or as a separate unit, powers a piston that pushes the blades apart with great force and spreads the seam. Once the seam has been spread, the now-open blades can be repositioned around the metal. The device is engaged in reverse and the blades close, cutting through metal. Repeating this process allows a rescuer to quickly open a gap wide enough to pull free a trapped victim. The blades can spread or cut with a force of several tons or kilonewtons with the tips of the blades spreading up to a meter.

This operation can also be performed by dedicated spreading and cutting tools, which are designed especially for their own operations and may be required for some rescues.

[edit] Rams

An Amkus Ram

Rams are used far less than spreader-cutters in auto rescues; nonetheless, they serve an important purpose. There are many types and sizes, including single-piston, dual-piston and telescopic rams. Sizes commonly vary from 50.80cm (20") to 178cm (70") (extended). Rams use more hydraulic fluid during operation than spreader-cutters, so it is essential that the pump being used have enough capacity to allow the ram to reach full extension.

History

A hydraulic spreader in use

Previously rescuers often used circular saws for vehicle extrication, but these suffered from several drawbacks. Saws can generate sparks, which could start a fire, create loud noise, which could stress the victim, and are often slow cutting. Alternately, rescuers could try to pry open the vehicle doors using a crowbar or halligan bar, but this could compromise the stability of the vehicle, further injure the victims, or unintentionally activate vehicle airbags.

In comparison, hydraulic spreader-cutters are quieter, faster, and more versatile: they can cut, open, and even lift a car. Jaws of Life is a trademarked line of tools originally developed by Hurst Performance for use in auto racing. The jaws of life derives its name from one of the coinventors Mr. Jack Allen Watson. When submitting drawings he would often sign them with his initials J.A.W. Over time the device came to be known unofficially within Hurst as Jaws. The name stuck. The device was later introduced as the Jaws of life. The hydraulic spreader was originally developed in 1972 by Hurst. Hurst later developed a cutter and a hydraulic ram. When an occupant is trapped the hurst tool is used to pry or cut the car to remove the occupant. It takes about two minutes to take the roof off a car.