Knife Totally Explained

A knife is a sharp-edged (single or double edged) instrument consisting of a thin blade used for cutting and fitted with a handle. The knife can be used as a tool or a weapon. Considered by some to be one of the most useful tools of all time, its origins date as far back as two-and-a-half million years ago, as evidenced by the Olduwan tools.

History

The earliest knives were shaped by percussion flaking from rock, particularly water-worn creek cobbles made out of volcanic rock. During the Paleolithic era Homo habilis likely made similar tools out of wood, bone, and similar highly perishable material that hasn't survived. As recent as five thousand years ago, as advances in metallurgy progressed, stone, wood, and bone blades were gradually succeeded by copper, bronze, iron, and eventually steel. Modern knives may be made from many different materials such as carbon fiber, ceramics, and titanium. Knives gained prominence during the Middle Ages as one of the three major items of cutlery in the western world, accompanying the fork and spoon, and in this way much of the world's population is exposed to knives on a daily basis. There is a very active community of modern custom knife makers and collectors. The American Bladesmith Society promotes forged blades; the Knifemakers Guild

promotes all custom knives.

Materials and construction

Today, knives come in many forms but can be categorized between two different types: fixed blade knives and folding, or pocket, knives. Although each has inherent advantages, the two have many similar characteristics. Modern knives consist of a blade (1) and handle (2). The blade can be fine or serrated. The handle, used to grip and manipulate the blade safely, may include the tang, a portion of the blade that extends into the handle. The blade consists of the point (3), the end of the knife used for piercing, the edge (4), the cutting surface of the knife extending from the point to the heel, the grind (5), the cross-section shape of the blade, the spine, (6), the top, thicker portion of the blade, the fuller (7), the groove added to lighten the blade, and the bolster (8), the thick portion of the blade joining the blade and the handle. The guard (9) is a barrier between the blade and the handle which protects the hand from an opponent, or the blade of the knife itself. A choil, where the blade is unsharpened and possibly indented as it meets the handle, may be used to prevent scratches to the handle when sharpening or as a forward-finger grip. The end of the handle, or butt (10), may allow a lanyard (11), used to secure the knife to the wrist.

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, hold its edge well, and remain 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 isn't 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 combine the best attributes of carbon steel and stainless steel. High carbon stainless steel blades don't discolor or stain, and maintain a sharp edge. Laminate blades use multiple metals to create a layered sandwich, combining the attributes of both. For example, a harder, more brittle steel may be sandwiched 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. Pattern-welding is similar 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 metal that's lighter, more wear resistant, 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 incredibly hard, lightweight blades; so hard that that'll maintain a sharp edge for months or years with no maintenance at all. They are immune to corrosion, but can only be sharpened on silicon carbide sandpaper and some grinding wheels. Plastic blades are not very sharp at all but are typically serrated, and are usually considered 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. With common kitchen cutlery, forged blades are often seen in more expensive knives. Forged blades can often be distinguished from stock removal blades by the presence of an integral bolster.
The edge of the knife can be sharpened to a cutting surface in a number of different ways. Flat ground blades have a profile that tapers from the thick spine to the sharp edge in a straight or convex line. Seen in cross section, the blade would form a long, thin triangle, or where the taper doesn't extend to the back of the blade, a long thin rectangle with one peaked side. Hollow ground blades have concave, beveled edges that are ground starting midway down the blade, instead of at the spine. The resulting blade has a thinner edge, so it may have better cutting ability, but it's lighter and less durable than flat ground blades. Serrated blade knives have a wavy, scalloped or saw-like blade. Serrations make knives ideal for cutting things that are hard on the outside and soft on the inside that might otherwise be damaged by a knife with a plain edge blade. Serrated knives cut much better than plain edge blade knives when dull, so they may last longer without sharpening, and require a special tool to be sharpened.

Fixed blade features

A fixed blade knife doesn't fold or slide, and is typically stronger due to the tang, the extension of the blade into the handle, and lack of movable parts.—to grave—so the dead wouldn't be defenseless in the next world. As such, 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 black-handled knife, is used in Wicca and other forms of modern 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. 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 is exchanged for the gift, rendering "payment."

Legislation

Knives are typically restricted by law, although restrictions vary greatly by country or state and type of knife. For example, some laws restrict carrying an unconcealed knife in public while other laws can restrict even private ownership of certain knives, such as switchblades.

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