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Anatomy of a knife A knife always has one or more uses. A knife may consist of a blade, a spine, a tang, a choil, and many other optional features. The blade may be separated from the handle by a bolster, a guard, and/or a subhilt. The tang is an extension of the blade into the handle. The bolster usually helps to join the blade to the handle and adds greater strength. Some bolsters also may function as a barrier, or handguard, to prevent fingers from slipping onto the blade. A bolster with a definite extension away from the handle often serves as a guard to further protect the hand when using a knife. Common blade features include serrations, coatings, and functional or decorative embellishments, including engraving, opening holes, thumb studs, disks and nail grooves. A fuller, sometimes mistakenly called a blood gutter or blood groove, is a depression along a blade. There is a myth that this promotes bleeding from a wound. The actual function is to lighten the blade without sacrificing stiffness. On many knives it is purely decorative. Additionally, a groove on the blade can reduce surface tension between the blade and the item being cut, thereby allowing easier movement or removal of the blade. Some knives have a choil where the blade is unsharpened and possibly indented as it meets the handle. A small choil is useful to prevent scratches (from sharpening) on the handle. A large choil is useful as a forward finger grip. Handles may be made of any solid material: wood, steel and decorative materials are common. A hole in the end of the handle allows the knife to be hung or placed on a lanyard. Knives are generally divided into folding knives and fixed blades. A folder stores the blade inside the handle, while a fixed blade needs a sheath or other storage method when not in use. The handle of a folder is built around a frame; on the inside may be liners, and on the outside there may be slabs. Folders may include a locking mechanism; there are many types, but the common locks are back locks and Walker locks (also called liner locks). Fixed blades may have single or multipart handles, usually attached to the blade's tang. A full-tang design extends the tang all the way through the handle; these are the strongest fixed blades. Activities that require a strong blade, such as hunting or fighting, typically rely on a fixed blade. Some famous fixed blade designs include the Ka-bar and Bowie knives. Blades There are hundreds of commercial manufacturers including Dexter-Russell, Forschner/Victorinox, Wüsthof, Global, Henckels, Kershaw Knives, SpyderCo, Benchmade and Böker (Tree Brand). There are also hundreds of small knifemaking shops, usually specializing in a few kinds of knives or custom work. Knifemaking is a popular hobby, as well. Materials Knife blades are typically made of steel, but obsidian, glass, titanium, ceramic and plastics are also used. Two recently introduced materials are Stellite and Talonite. There are a large number of alloys used as knife steels, mostly variants of high-carbon steel and stainless steels. Most knife steel is tempered martensite, which has a fine-grained crystal structure with lattice irregularities that make it hard. It is formed by quenching, changing it from the austenitic structure of a high temperature to a harder structure. The blade is then tempered by heating to an intermediate temperature for a period to reduce britlleness. A knife steel usually has fairly low nickel content, because nickel tends to keep steel in the austenitic structure even when cold. Steels having high carbon but low chromium content ("carbon steel") are prone to rust and pitting if not kept dry and oiled. Stainless steel knives began gaining popularity during the second quarter of the twentieth century. Stainless steel is steel with very high (12–18%) alloy content, usually chromium — stainless knife steels may be high in carbon, but "carbon steel" means there are few or no additional alloying ingredients. Stainless steel is relatively resistant to corrosion (though knife steel is less so than higher nickel stainless steel) because, except in acid, one of the metals or one of the oxides is always stable. The alloy disruptions to the crystal lattice explain the reputation of stainless steels for long wear (the carbides are harder than the metal) and for being harder to sharpen than a rustable, low alloy ("carbon") steel. Harder steels can take sharper edges. The bulk hardness and toughness of stainless steel tend to be lower than those of low alloy steel. Common stainless knife steels include 154CM and ATS-34, 420M, AUS8 and AUS10, 440A and 440C, VG10, S30V, CPM440V and others. Common high-hardness knife steels (tool steel) include D2 and M2. Knifemakers sometimes use titanium, cobalt, and other alloys. These are more ductile than typical stainless steels, but have vocal supporters despite concerns about health effects of cobalt content. Damascus steel is made by a set of techniques for mixing several steels. The cost of the process restricts it to high-end knives. There is typically more demand for exotic alloys in the utility, outdoor, and tactical or combat knife categories than there is for kitchen knives. Vanadium and molybdenum are important alloy metals because they make the grain size smaller, which improves hardness and toughness. Vanadium and molybdenum may increase corrosion resistance, although work by CATRA (Cutlery Allied Trades Research Association) has found no anti-corrosive benefits from vanadium. Chromium is the major anticorrosive component in most knife materials. Some manufacturers, particularly of kitchen knives, make ceramic blades; these are harder and stay sharp longer than steel, but because of their brittleness chip and break more readily. Shapes
Locks Most folding knives have a locking mechanism. The most traditional and commonplace lock is the slip-joint. This is not really a lock at all, and is found most commonly on traditional pocket knives. It consists of a backspring that wedges itself into a notch on the tang on the back of the blade. The lockback is the simplest and most common true locking knife. It is like a slip-joint, but the lock includes a pivoted latch connected to a spring. To disengage, one presses the latch on the spine of the knife down, releasing the tang. The linerlock, or Walker lock is also common today. Its main advantage is that it allows the lock to be disengaged with one hand. When the blade opens, a bent liner presses against the rear of the tang, preventing it from swinging back. To disengage, the liner is pulled back to the side of the knife. The framelock is a variant of the liner lock in which the frame functions as the spring. It is often more secure than a liner lock because it does not require as close a tolerance in manufacture. There are many other modern locks with various degrees of effectiveness. Most of these are particular to single brands, notably Benchmade's AXIS™ lock and SpyderCo's Compression™ lock. Many folding knives (particularly locking models) have a small knob, disk or hole that allows the user to open the knife quickly with one hand. Another approach is the Carson flipper, a bump protruding from the blade's choil that may be pushed down when the blade is closed. Function In general, knives are either working knives (everyday-use blades), or fighting knives. Some knives, such as the Scottish or dirk and Japanese Tantō function in both roles. Many knives are specific to a particular activity or occupation: Indoor use
Outdoor use
Sharpening Knives are sharpened by grinding against a hard rough surface, typically stone, or a soft surface with hard particles, such as sandpaper. For finer sharpening, a leather razor strap, or strop, is often used. The smaller the angle between the blade and stone, the sharper the knife will be, but the less side force is needed to bend the edge over or chip it off. Very sharp knives sharpen at 10 degrees. Typical knives are sharpened at 15 degrees. Knives that require a tough edge (such as those that chop) sharpen at 20 degrees or more. For an extremely durable edge (such as a chisel or drawknife), blades can be sharpened to 30 degrees. In general, the harder the material to be cut the higher the angle of the edge. The composition of the stone affects the sharpness of the blade (finer grain produces sharper blades), as does the composition of the blade (some metals take and keep an edge better than others). Clamp-style sharpening tools use a clamp with several holes with pre-defined angles. The stone is mounted on a rod and is pulled through these holes, so that the angle remains consistent. Another system is the crock stick setup, where two sticks are put into a plastic or wooden base to form a V shape. When the knife is pulled up the V, the angle is held so long as the blade is held perpendicular to the base. Honing stones (also called whetstones) come with coarse and fine grits and can be described as hard or soft based on whether the grit comes free. Arkansas is a traditional source for honing stones, which are traditionally used with water or honing oil. India is another traditional source for stones. Ceramic hones are also common, especially for fine grit size. Water stones (both artificial and natural) come in very fine grits. They are stored in water, and develop a layer of slurry which dulls the edge if the blade is honed as if honing into the stone. Generally, these are more costly than oilstones. Coated hones, which have an abrasive, sometimes diamonds, on a base of plastic or metal, are also available. Sharpening blocks made with corundum are expensive. Stropping a knife is a finishing step. This is often done with a leather strap impregnated with abrasive compounds, but can be done on paper, cardstock, or even cloth in a pinch. It will not cut the edge significantly, but produces a very sharp edge with very little metal loss. It is useful when a knife is still sharp, but has lost that 'scary sharp' edge from use. Maintenance may be done with a steel. This process can affect alignment of the edge. Realigning the edge can keep a knife sharp as often a rolled edge is responsible for dullness. A very sharp knife has an edge that is too small to see with the eye; it may even be hard to focus in a microscope. The shape near the edge can be highlighted by rotating the knife and watching changes in reflection. Nicks and rolled edges can also be seen. If a knife is used as a scraper, a prybar, or encounters hard particles in softer materials or is used asymmetrically, there may be a sideways load at the tip. This may damage the knife. Legal considerations Countries, states, and smaller subdivisions may regulate the ownership, sale, carry or use of any knife or type of knife, whether designed as tool or weapon. Again, always check your local laws. Carrying knives in public is forbidden by law in many countries. Exceptions may be made for hunting knives, and for knives used for work-related purposes (e.g. chef's knives). Automatic knives (switchblades) are often banned from civilian carry or possession. Butterfly knifes (Balisong) are also frequently restricted due to an impression of connection with gang activity. A notable exception is Austria, where civilian possession of automatic knives including double-edged automatic OTF ("out The front") daggers is allowed. Most Western European nations are very unfriendly toward all knives other than small pocket knives and similar small tools. Carrying knives on commercial airplanes is subject to many prohibitions which vary too frequently to be listed here. Knives can normally be transported by air travellers if securely packed in hold luggage, where they will be inacessible during the flight. Consult your local laws, and ask about restrictions at the airport and at your destination. Any pocket knife or tool may be prohibited. In the USA Knife laws vary tremendously from state to state, and even from city to city inside a state. In Texas, for example, individuals may carry knives openly or concealed so long as they are single-edged, and are not daggers, switchblades, or gravity knives (Butterfly knife legality is questionable — there have been convictions). In some other states, fixed-blade knives are banned, open carry is banned, and sometimes concealed carry of anything except pocket knives is banned. Cities have ordinances further restricting these laws; in San Antonio, TX, it is a violation to carry a folding knife having a locking blade. California allows switchblades with blades less than two inches long. In some metro areas such as Washington, D.C., going into office buildings or museums, or simply loitering while carrying even small 3" folding knives can be problematic. Other restricted areas in the U.S. include court buildings, federal property (which technically limits blades to 2.5-inches), and public school grounds. In the UK Knife possession is legislated differently in public places and in private. In private, you can own any type of knife except automatic knives (flick knives, butterfly knives, and switchblades). In general, knives carried in public places are legally considered to be offensive weapons and the carrier can be charged with "possession of an offensive weapon". It is however legal to carry a knife if there is a bona fide reason to do so for example, if it is a tool required for ones trade (e.g. chefs) or if it is part of a national costume (e.g. sgian dubh), or if it is carried for religious reasons (e.g. Sikh Kirpan). A special exception exists for penknives (pocket knives) which are legal without reason for possession, but they must be non-locking and sub 3". Any other article with a blade or point is illegal to possess in a public place, except with a reasonable excuse. *Even a folding pocket knife of less than 3" may still be considered an offensive weapon if carried or used for that purpose. In Japan With the exception of any type of switchblade, you may carry any knife shorter than 15cm (about 5.9in). To carry knives, the length of blades must be shorter than 6cm (switchblade 5.5cm). (It is strictly prohibited to carry them as defensive weapons.) If people need to carry their knives, they must be concealed and cannot be taken out easily from their sheaths. The Japanese Guns and Knives Control Law is relatively tolerant toward knives which can be opened using a single hand. Any type of butterfly knife is legal. With the exception of possessing Japanese Katana, Japanese traditional swords are regarded as offensive weapons. However, if they have artistic values, people may possess one as long as it is registered. If you carry 6cm and longer blade(or deadly), you may receive up to 1 year in prison, or ¥300,000 or about U.S. $2,700 fine. Knife modifications Knives can be customised to the user and/or application: Knife superstitions In some places it is traditionally believed that the giving of a knife as a gift to a friend will cut or sever the relationship. To avoid such ill luck, the receiver should give a coin in return so as to "pay" for the gift. It is common to include a penny, often taped to the blade, with a knife given as a gift which the receiver is to return as "payment". Stirring liquids or powders with a knife is often considered unlucky. One rhyme says, "Stir with a knife, stir up strife". In some cultures giving a knife as a gift is considered a sign of respect and trust. This is especially true in Finland where various non-governmental organizations, clubs and even government agencies traditionally give a puukko (a Finnish fixed-blade hunting/outdoor knife) as a gift to trusted employers or contacts. The puukko is always presented handle first as a sign of trust and friendly intentions. In many places in the United States it is considered bad luck to hand an open, folding blade knife to someone. This is especially true in more rural areas where carrying a pocket knife is as common as carrying a set of keys. This may stem from safety issues. It is also believed that allowing someone to close a folding blade knife that you have opened is bad luck. Just as with swords, regional and cultural superstitions exist regarding the treatment of knives that are used in combat. One common superstition states that it is bad luck to return a combat knife from its sheath without using it to draw blood. A variant myth exists surrounding drawing a knife (e.g. a sgian dubh) without drawing the blood of a cultural enemy (e.g an Englishman). Sometimes these superstitions are actually attempts to insult the culture of the supposed believer. Some cultures believe that a knife does not belong to an individual until it has 'bit' them, or tasted their blood. Believers in such superstitions may intentionally prick a finger on the blade of a knife rather than risk a later, accidental cut. According to this superstition, the knife will stay sharp longer and is less likely to accidentally cut its owner once it has tasted his or her blood. In some parts of America, it is considered bad luck to sharpen a knife, or any blade, after dark. Further reading See also | |||||||||||||||
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