knife

Parts

A modern knife consists of:

the blade

the handle

the point – the end of the knife used for piercing

the edge – the cutting surface of the knife extending from the point to the heel

the grind – the cross section shape of the blade

the spine – the thickest section of the blade; on a single-edged knife, the side opposite the edge; on a two-edged knife, more toward the middle

the fuller – a groove added to make the blade lighter (optional)

the ricasso – the flat section of the blade located at the junction of the blade and the knife's bolster or guard (optional)

the guard – the barrier between the blade and the handle which prevents the hand from slipping forward onto the blade and protects the hand from the external forces that are usually applied to the blade during use (optional)

the hilt or butt – the end of the handle used for blunt force

the lanyard – a strap used to secure the knife to the wrist (optional)

The blade edge can be plain or serrated, or a combination of both. Single-edged knives may have a reverse edge or false edge occupying a section of the spine. These edges are usually serrated and are used to further enhance function.

The handle, used to grip and manipulate the blade safely, may include a tang, a portion of the blade that extends into the handle. Knives are made with partial tangs (extending part way into the handle, known as "stick tangs") or full tangs (extending the full length of the handle, often visible on top and bottom). There is also the enterçado construction method present in antique knives from Brazil, such as the Sorocaban Knife, which consists in riveting a repurposed blade to the ricasso of a bladeless handle. The handle may include a bolster, a piece of heavy material (usually metal) situated at the front or rear of the handle. The bolster, as its name suggests, is used to mechanically strengthen the knife.

Blade

Knife blades can be manufactured from a variety of materials, each of which has advantages and disadvantages. Carbon steel, an alloy of iron and carbon, can be very sharp. It holds its edge well, and remains easy to sharpen, but is vulnerable to rust and stains. Stainless steel is an alloy of iron, chromium, possibly nickel, and molybdenum, with only a small amount of carbon. It is not able to take quite as sharp an edge as carbon steel, but is highly resistant to corrosion. High carbon stainless steel is stainless steel with a higher amount of carbon, intended to incorporate the better attributes of carbon steel and stainless steel. High carbon stainless steel blades do not discolor or stain, and maintain a sharp edge. Laminated blades use multiple metals to create a layered structure, combining the attributes of both. For example, a harder, more brittle steel may be pressed between an outer layer of softer, tougher stainless steel to reduce vulnerability to corrosion. In this case, however, the part most affected by corrosion, the edge, is still vulnerable. Damascus steel is a form of pattern welding with similarities to laminate construction. Layers of different steel types are welded together, but then the stock is manipulated to create patterns in the steel.

Titanium is a metal that has a higher strength-to-weight ratio and more flexible than steel. Although less hard and unable to take as sharp an edge, carbides in the titanium alloy allow them to be heat-treated to a sufficient hardness. Ceramic blades are hard, brittle, lightweight, and do not corrode: they may maintain a sharp edge for years with no maintenance at all, but are fragile and will break if dropped on a hard surface or twisted in use. They can only be sharpened on silicon carbide sandpaper and appropriate grinding wheels. Plastic blades are not sharp and are usually serrated to enable them to cut. They are often disposable.

Steel blades are commonly shaped by forging or stock removal. Forged blades are made by heating a single piece of steel, then shaping the metal while hot using a hammer or press. Stock removal blades are shaped by grinding and removing metal. With both methods, after shaping, the steel must be heat treated. This involves heating the steel above its critical point, then quenching the blade to harden it. After hardening, the blade is tempered to remove stresses and make the blade tougher. Mass manufactured kitchen cutlery uses both the forging and stock removal processes. Forging tends to be reserved for manufacturers' more expensive product lines, and can often be distinguished from stock removal product lines by the presence of an integral bolster, though integral bolsters can be crafted through either shaping method.

Handle

The handles of knives can be made from a number of different materials, each of which has advantages and disadvantages. Handles are produced in a wide variety of shapes and styles. Handles are often textured to enhance grip.

Wood handles provide good grip and are warm in the hand, but are more difficult to care for. They do not resist water well, and will crack or warp with prolonged exposure to water. Modern stabilized and laminated woods have largely overcome these problems. Many beautiful and exotic hardwoods are employed in the manufacture of custom and some production knives. In some countries it is now forbidden for commercial butchers' knives to have wood handles, for sanitary reasons.

Plastic handles are more easily cared for than wooden handles, but can be slippery and become brittle over time.

Injection molded handles made from higher grade plastics are composed of polyphthalamide, and when marketed under trademarked names such as Zytel or Grivory, are reinforced with Kevlar or fiberglass. These are often used by major knife manufacturers.

Rubber handles such as Kraton or Resiprene-C are generally preferred over plastic due to their durable and cushioning nature.

Micarta is a popular handle material on user knives due to its toughness and stability. Micarta is nearly impervious to water, is grippy when wet, and is an excellent insulator. Micarta has come to refer to any fibrous material cast in resin. There are many varieties of micarta available. One very popular version is a fiberglass impregnated resin called G-10.

Leather handles are seen on some hunting and military knives, notably the KA-BAR. Leather handles are typically produced by stacking leather washers, or less commonly, as a sleeve surrounding another handle material. Russian manufacturers often use birchbark in the same manner.

Skeleton handles refers to the practice of using the tang itself as the handle, usually with sections of material removed to reduce weight. Skeleton handled knives are often wrapped with parachute cord or other wrapping materials to enhance grip.

Types

Weapons

As a weapon, the knife is universally adopted as an essential tool. It is the essential element of a knife fight. For example:

Ballistic knife: A specialized combat knife with a detachable gas- or spring-propelled blade that can be fired to a distance of several feet or meters by pressing a trigger or switch on the handle.

Bayonet: A knife-shaped close-quarters combat weapon designed to attach to the muzzle of a rifle or similar weapon.

Butterfly knife: A folding pocket knife also known as a "balisong" or "batangas" with two counter-rotating handles where the blade is concealed within grooves in the handles.

Combat knife: Any knife intended to be used by soldiers in the field, as a general-use tool, but also for fighting.

Dagger: A single-edged or double-edged combat knife with a central spine and edge(s) sharpened their full length, used primarily for thrusting or stabbing. Variations include the Stiletto and Push dagger. See List of daggers for a more detailed list.

Fighting knife: A knife with a blade designed to inflict a lethal injury in a physical confrontation between two or more individuals at very short range (grappling distance). Well known examples include the Bowie knife, Ka-Bar combat knife, and the Fairbairn–Sykes fighting knife.

Machete: A knife with a broad blade designed for chopping, often curved either in a convex or concave fashion.

Shiv: A crudely made homemade knife out of everyday materials, especially prevalent in prisons among inmates. An alternate name in some prisons is shank.

Sword: An evolution of the knife with a lengthened and strengthened blade used primarily for mêlée combat and hunting.

Sports equipment

Throwing knife: A knife designed and weighted for throwing.

Utensils

A primary aspect of the knife as a tool includes dining, used either in food preparation or as cutlery. Examples of this include:

Bread knife: A knife with a serrated blade for cutting bread

Boning knife: A knife used for removing the bones of poultry, meat, and fish.

Fillet Knife: A knife a with flexible blade used to separate meat or fish from bones.

Butcher's Knife: A knife designed and used primarily for the butchering and/or dressing of animals.

Carving knife: A knife for carving large cooked meats such as poultry, roasts, hams, and other large cooked meats.

Canelle or Channel knife: The notch of the blade is used to cut a twist from a citrus fruit, usually in the preparation of cocktails

Chef's knife: Also known as a French knife, a cutting tool used in preparing food

Cleaver: A large knife that varies in its shape but usually resembles a rectangular-bladed hatchet. It is used mostly for hacking through bones as a kitchen knife or butcher knife, and can also be used for crushing via its broad side, typically garlic.

Electric knife: An electrical device consisting of two serrated blades that are clipped together, providing a sawing action when powered on

Kitchen knife: Any knife, including the chef's knife, that is intended to be used in food preparation

Oyster knife: Has a short, thick blade for prying open oyster shells

Tools

As a utility tool the knife can take many forms, including:

Bowie knife: Commonly, any large sheath knife, or a specific style of large knife popularized by Jim Bowie.

Bushcraft knife: A sturdy, normally fixed blade knife used while camping in the wilderness.

Camping knife: A camping knife is used for camping and survival purposes in a wilderness environment.

Head knife or Round knife: A knife with a semicircular blade used since antiquity to cut leather.

Crooked knife: Sometimes referred to as a "curved knife", "carving knife" or in the Algonquian language the "mocotaugan" is a utilitarian knife used for carving.

Diver's knife: A knife adapted for use in diving and water sports and a necessary part of standard diving dress.

Electrician's knife: A short-bladed knife used to cut electrical insulation. Also, a folding knife with a large screw driver as well as a blade. Typically the screwdriver locks, but the blade may not lock.

Folding knife: A folding knife is a knife with one or more blades that fit inside the handle that can still fit in a pocket. It is also known as a jackknife or jack-knife.

Hunting knife: A knife used to dress large game.

Kiridashi: A small Japanese knife having a chisel grind and a sharp point, used as a general-purpose utility knife.

Linoleum knife: is a small knife that has a short, stiff blade with a curved point and a handle and is used to cut linoleum or other sheet materials.

Traditional and religious implements

Athame: A typically black-handled and double-edged ritual knife used in Wicca and other derivative forms of Neopagan witchcraft. (see also Boline).

Dirk: A long bladed thrusting dagger worn by Scottish Highlanders for customary and ceremonial purposes.

Katar: An Indian push dagger sometimes used ceremonially.

Kilaya: A dagger used in Tibetan Buddhist rituals.

Kirpan: A ceremonial knife that all baptised Sikhs must wear as one of the five visible symbols of the Sikh faith (Kakars)

Kris: A dagger used in Indo-Malay cultures, often by nobility and sometimes in religious rituals

Kukri: A Nepalese knife used as a tool and weapon

Maguro bōchō: A traditional Japanese knife with a long specialized blade that is used to fillet large ocean fish.

Puukko: A traditional Finnish style woodcraft belt-knife used as a tool rather than a weapon

Seax: A Germanic single-edged knife, dagger or short sword used both as a tool and as a weapon.

Sgian-dubh: A small knife traditionally worn with the Highland and Isle dress (Kilt) of Scotland.

Ulu: An Inuit woman's all-purpose knife with a handle directly above a highly curved blade.

Yakutian knife: A traditional Yakuts knife used as a tool for wood carving and meat or fish cutting. Can be used as a part of yakutian ethnic costume.

Rituals and superstitions

The knife plays a significant role in some cultures through ritual and superstition, as the knife was an essential tool for survival since early man. Knife symbols can be found in various cultures to symbolize all stages of life; for example, a knife placed under the bed while giving birth is said to ease the pain, or, stuck into the headboard of a cradle, to protect the baby; knives were included in some Anglo-Saxon burial rites, so the dead would not be defenseless in the next world. The knife plays an important role in some initiation rites, and many cultures perform rituals with a variety of knives, including the ceremonial sacrifices of animals. Samurai warriors, as part of bushido, could perform ritual suicide, or seppuku, with a tantō, a common Japanese knife. An athame, a ceremonial knife, is used in Wicca and derived forms of neopagan witchcraft.

In Greece, a black-handled knife placed under the pillow is used to keep away nightmares. As early as 1646 reference is made to a superstition of laying a knife across another piece of cutlery being a sign of witchcraft. A common belief is that if a knife is given as a gift, the relationship of the giver and recipient will be severed. Something such as a small coin, dove or a valuable item is exchanged for the gift, rendering "payment."

Legislation

Some types of knives are restricted by law, and carrying of knives may be regulated, because they are often used in crime, although restrictions vary greatly by jurisdiction and type of knife. For example, some laws prohibit carrying knives in public while other laws prohibit possession of certain knives, such as switchblades.