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51-480: Blades function by concentrating force at the cutting edge. Design variations, such as serrated edges found on bread knives and saws , serve to enhance this force concentration, adapting blades for specific functions and materials. Blades thus hold a significant place both historically and in contemporary society, reflecting an evolution in material technology and utility. During food preparation, knives are mainly used for slicing, chopping, and piercing. In combat,

102-409: A blade may be used to slash or puncture, and may also be thrown or otherwise propelled . The function is to sever a nerve, muscle or tendon fibers, or blood vessel to disable or kill the adversary. Severing a major blood vessel typically leads to death due to exsanguination . Blades may be used to scrape, moving the blade sideways across a surface, as in an ink eraser , rather than along or through

153-415: A body that is tough. Prehistorically, and in less technologically advanced cultures even into modern times, tool and weapon blades have been made from wood, bone, and stone. Most woods are exceptionally poor at holding edges and bone and stone suffer from brittleness making them suffer from fracture when striking or struck. In modern times stone, in the form of obsidian, is used in some medical scalpels as it

204-469: A convex section to avoid getting stuck in the wood where chopping axes can be flat or even concave. A khopesh , falchion , or kukri is angled and/or weighted at the distal end so that force is concentrated at the faster moving, heavier part of the blade maximizing cutting power and making it largely unsuitable for thrusting, whereas a rapier is thin and tapered allowing it to pierce and be moved with more agility while reducing its chopping power compared to

255-456: A faster cut, but a plain edge has a cleaner cut. Some prefer a serrated blade on a pocket knife or on an emergency rescue knife, especially with the latter for its increased ability to cut through cords, ropes, and safety belts. Serration Serration is a saw -like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than

306-407: A firmer or tougher outer crust or skin without crushing the softer and more delicate inner crumb or flesh. Serrations give the blade's cutting edge less contact area than a smooth blade, which increases the applied pressure at each point of contact, and the points of contact are at a sharper angle to the material being cut. This causes a cutting action that involves many small splits in the surface of

357-407: A firmer or tougher outer crust or skin without crushing the softer and more delicate inner crumb or flesh. Serrations give the blade's cutting edge less contact area than a smooth blade, which increases the applied pressure at each point of contact, and the points of contact are at a sharper angle to the material being cut. This causes a cutting action that involves many small splits in the surface of

408-418: A low elastic modulus (is soft) but high yield strain (loosely, can be stretched or squashed by a large proportion without breaking), drawing serrations across the loaf with little downward force will allow each serration to simultaneously cut the bread with much less deformation of the loaf. Similarly, pushing on a rope tends to squash the rope while drawing serrations across it sheers the rope fibers. Drawing

459-404: A material into dust along a narrow channel, the kerf , whereas knives and similar act by forcing the material apart. This means that saws result in a loss of material and the serrations of a saw also serve to carry metal swarf and sawdust out of the cut channel.) Fullers are longitudinal channels either forged into the blade or later machined/milled out of the blade though the latter process

510-423: A material that is about as hard , though usually harder, than the material to be cut. Insufficiently hard blades will be unable to cut a material or will wear away quickly as hardness is related to a material's ability to resist abrasion . However, blades must also be tough enough to resist the dynamic load of impact and as a general rule the harder a blade the less tough (the more brittle) a material. For example,

561-512: A proper cut without an edge, and so in competitive fencing such attacks reward no points. Some variations include: Blades are sometimes marked or inscribed, for decorative purposes, or with the mark of either the maker or the owner. Blade decorations are often realized in inlay in some precious metal (gold or silver). Early blade inscriptions are known from the Bronze Age , a Hittite sword found at Hattusa bears an inscription chiseled into

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612-608: A serrated edge, which, somewhat counterintuitively, reduces fraying by reducing the average length of a thread that may be pulled from the edge. A type of serration is also found in airframe shapes used in certain stealth aircraft , which use the jaggedness of the serrated edge to deflect radar signals from seams and edges where a straight, non-serrated edge would reflect radar signals to the source. Screw threads show serration in profile, although they are usually shown in abbreviated or symbolic fashion on mechanical drawings to save time and ink. Brogue shoes are made with serrated edges on

663-608: A serrated edge, which, somewhat counterintuitively, reduces fraying by reducing the average length of a thread that may be pulled from the edge. A type of serration is also found in airframe shapes used in certain stealth aircraft , which use the jaggedness of the serrated edge to deflect radar signals from seams and edges where a straight, non-serrated edge would reflect radar signals to the source. Screw threads show serration in profile, although they are usually shown in abbreviated or symbolic fashion on mechanical drawings to save time and ink. Brogue shoes are made with serrated edges on

714-399: A similarly sized sword. A serrated edge, such as on a saw or a bread knife , concentrates force onto the tips of the serrations which increases pressure as well as allowing soft or fibrous material (like wood, rope, bread, and vegetables) to expand into the spaces between serrations. Whereas pushing any knife, even a bread knife, down onto a bread loaf will just squash the loaf as bread has

765-547: A smooth blade is less effective as the blade is parallel to the direction draw but the serrations of a serrated blade are at an angle to the fibers. Serrations on knives are often symmetric allowing the blade to cut on both the forward and reverse strokes of a cut, a notable exception being Veff serrations which are designed to maximize cutting power while moving the blade away from the user. Saw blade serrations, for both wood and metal, are typically asymmetrical so that they cut while moving in only one direction. (Saws act by abrading

816-404: A smooth blade or other edge, the applied pressure at each point of contact is greater, and the points of contact are at a sharper angle to the material being cut. This causes a cutting action that involves many small splits in the surface of the material being cut, which cumulatively serve to cut the material along the line of the blade. In nature, serration is commonly seen in the cutting edge on

867-413: A steel axehead is much harder than the wood it is intended to cut and is sufficiently tough to resist the impact resulting when swung against a tree while a ceramic kitchen knife, harder than steel, is very brittle (has low toughness) and can easily shatter if dropped onto the floor or twisted while inside the food it is cutting or carelessly stored under other kitchen utensils. This creates a tension between

918-423: A surface. For construction equipment such as a grader , the ground-working implement is also referred to as the blade, typically with a replaceable cutting edge. A simple blade intended for cutting has two faces that meet at an edge. Ideally, this edge would have no roundness but in practice, all edges can be seen to be rounded to some degree under magnification either optically or with an electron microscope. Force

969-408: A thinner one of similar design while also making it experience more drag while slicing or piercing. A filleting knife will be thin enough to be very flexible while a carving knife will be thicker and stiffer; a dagger will be thin so it can pierce, while a camping knife will be thicker so it can be stronger and more durable. A strongly curved edge, like a talwar , will allow the user to draw the edge of

1020-568: A wide range of physical and chemical properties desirable for blades. For example, surgical scalpels are often made of stainless steel so that they remain free of rust and largely chemically inert; tool steels are hard and impact resistant (and often expensive as retaining toughness and hardness requires expensive alloying materials, and, being hard, they are difficult to make into their finished shape) and some are designed to resist changes to their physical properties at high temperatures. Steels can be further heat treated to optimize their toughness, which

1071-497: Is also known as a dentated, sawtooth, or toothed blade. Many such blades are scalloped , having edges cut with curved notches, common on wood saws and bread knives . With kitchen knives, the finer serrated edge is found typically on paring and cheese knives, particularly for slicing harder cheeses like cheddar or Wensleydale. The wider scalloped-edge serrations are found on practically all bread knives and typically on fruit knives. These serrated knives are better able to cut through

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1122-497: Is also known as a dentated, sawtooth, or toothed blade. Many such blades are scalloped , having edges cut with curved notches, common on wood saws and bread knives . With kitchen knives, the finer serrated edge is found typically on paring and cheese knives, particularly for slicing harder cheeses like cheddar or Wensleydale. The wider scalloped-edge serrations are found on practically all bread knives and typically on fruit knives. These serrated knives are better able to cut through

1173-418: Is applied it them, forming a section like the bottom part of a letter "J". For this reason, straight edge razors are frequently stropped to straighten the edge. Drawing a blade across any material tends to abrade both the blade, usually making it duller, and the cut material. Though softer than glass or many types of stone used in the kitchen, steel edges can still scratch these surfaces. The resulting scratch

1224-414: Is applied to the blade, either from the handle or pressing on the back of the blade. The handle or back of the blade has a large area compared to the fine edge. This concentration of applied force onto the small edge area increases the pressure exerted by the edge. It is this high pressure that allows a blade to cut through a material by breaking the bonds between the molecules, crystals, fibers, etc. in

1275-461: Is capable of being formed into an exceedingly fine edge. Ceramic knives are non-metallic and non-magnetic. As non-metals do not corrode they remain rust and corrosion free but they suffer from similar faults as stone and bone, being rather brittle and almost entirely inflexible. They are harder than metal knives and so more difficult to sharpen, and some ceramic knives may be as hard or harder than some sharpening stones. For example, synthetic sapphire

1326-413: Is commonly seen in the cutting edge on the teeth of some species, usually sharks . However, it also appears on non-cutting surfaces, for example, in botany where a toothed leaf margin or other plant part, such as the edge of a carnation petal, is described as being serrated. A serrated leaf edge may reduce the force of wind and other natural elements. Probably the largest serrations on Earth occur on

1377-447: Is full of very fine particles of ground glass or stone which will very quickly abrade the blade's edge and so dull it. In times when swords were regularly used in warfare, they required frequent sharpening because of dulling from contact with rigid armor, mail, metal rimmed shields, or other swords, for example. Particularly, hitting the edge of another sword by accident or in an emergency could chip away metal and even cause cracks through

1428-717: Is harder than natural sharpening stones and is as hard as alumina sharpening stones. Zirconium dioxide is also harder than garnet sharpening stones and is nearly as hard as alumina. Both require diamond stones or silicon carbide stones to sharpen and care has to be taken to avoid chipping the blade. As such ceramic knives are seldom used outside of a kitchen and they are still quite uncommon. Plastic knives are difficult to make sharp and poorly retain an edge. They are largely used as low cost, disposable utensils or as children's utensils or in environments such as air travel where metal blades are prohibited. They are often serrated to compensate for their general lack of sharpness but, as evidenced by

1479-477: Is important for impact blades, or their hardness, which allows them to retain an edge well with use (although harder metals require more effort to sharpen). It is possible to combine different materials, or different heat treatments, to produce desirable qualities in a blade. For example, the finest Japanese swords were routinely made of up to seven sections of metals and even poorer quality swords were often made of two. These would include soft irons that could absorb

1530-454: Is less desirable. This loss of material necessarily weakens the blade but serves to make the blade lighter without sacrificing stiffness. The same principle is applied in the manufacture of beams such as I-beams . Fullers are only of significant utility in swords. In most knives there is so little material removed by the fuller that it makes little difference to the weight of the blade and they are largely cosmetic. Typically blades are made from

1581-418: Is particularly true of acute blades and those made of soft materials. Dulling usually occurs due to contact between the blade and a hard substance such as ceramic, stone, bone, glass, or metal. The more acute the blade, the more easily it will dull. As the blade near the edge is thinner, there is little material to remove before the edge is worn away to a thicker section. Thin edges can also roll over when force

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1632-440: Is poorly suited for working stone. Bronze is superior in this regard, and was taken up by later civilizations. Both bronze and copper can be work hardened by hitting the metal with a hammer. With technological advancement in smelting, iron came to be used in the manufacturing of blades. Steel , a range of alloys made from iron, has become the metal of choice for the modern age. Various alloys of steel can be made which offer

1683-483: The teeth of some species, usually sharks . However, it also appears on non-cutting surfaces, for example, in botany where a toothed leaf margin or other plant part, such as the edge of a carnation petal, is described as being serrated. A serrated leaf edge may reduce the force of wind and other natural elements. Probably the largest serrations on Earth occur on the skylines of mountains (the Spanish word sierra , as in

1734-469: The Sierra Nevada, means a saw). These occur due to the uneven action of landform edges pushing rock upwards, and the uneven action of erosion . Human uses of serration have copied, and gone beyond, those found in nature. For example, the teeth on a saw or other serrated blade serve a similar cutting or scraping purpose as the serration of an animal tooth. Tailors use pinking shears to cut cloth with

1785-414: The blade across the opponent's body and back. For straight-edged weapons, many recorded techniques feature cleaving cuts, which deliver the power out to a point, striking directly in at the target's body, done to split flesh and bone rather than slice it. That being said, there also exist many historical slicing techniques for straight-edged weapons. Hacking cuts can be followed by a drawing action to maximize

1836-420: The blade against an opponent even while close to the opponent where a straight sword would be more difficult to pull in the same fashion. The curved edge of an axe means that only a small length of the edge will initially strike the tree, concentrating force as does a thinner edge, whereas a straight edge could potentially land with the full length of its edge against a flat section of the tree. A splitting maul has

1887-539: The blade. Soft-cored blades are more resistant to fracturing on impact. Folding pocket knives often have a groove cut in the side of the blade near the spine. This is called a nail pull and allows the fingernail to be inserted to swing the blade out of the holder. Some of the most common shapes are listed below. The sharp edges of a sword may be either curved or straight. Curved blades tend to glide more easily through soft materials, making these weapons more ideal for slicing. Techniques for such weapons feature drawing

1938-459: The bronze, stating that the blade was deposited as an offering to the storm-god by king Tuthaliya . Blade inscriptions become particularly popular in the 12th century knightly sword , based on the earlier, 9th to 11th century, the tradition of the so-called Ulfberht swords . Serrated edge Serration is a saw -like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with

1989-441: The cut's effectiveness. For more information see Western Martial Arts or kenjutsu . Some weapons are made with only a single leading edge, such as the sabre or dusack . The dusack has a 'false edge' near the tip, which only extends down a portion of the blade's backside. Other weapons have a blade that is entirely dull except for a sharpened point, like the épée or foil , which prefer thrusts over cuts. A blade cannot perform

2040-426: The energy of impact without fracturing but which would bend and poorly retain an edge, and hard steels more liable to shatter on impact but which retained an edge well. The combination provided a sword that would resist impact while remaining sharp, even though the edge could chip if abused. Pattern welding involved forging together twisted bars of soft (bendable) low carbon and hard (brittle) higher carbon iron. This

2091-408: The fact they can cut food, they are still capable of inflicting injury. Plastic blades of designs other than disposable cutlery are prohibited or restricted in some jurisdictions as they are undetectable by metal detectors. Native copper was used to make blades by ancient civilizations due to its availability. Copper's comparative softness causes it to deform easily; it does not hold an edge well and

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2142-411: The intended use of the blade, the material it is to be made from, and any manufacturing processes (such as heat treatment in the case of steel blades that will affect a blade's hardness and toughness). A balance must be found between the sharpness and how well it can last. Methods that can circumvent this include differential hardening . This method yields an edge that can hold its sharpness as well as

2193-501: The leather pieces, for no known purpose at all other than style. The step clamp and step block assembly in metalworking adopt serration for the purpose of applying clamping pressure from an adjustable position. Humans have used serrated blades since the Mesolithic era, when prehistoric humans made these from flint . A serrated blade has a toothlike rather than a plain edge, and is used on saws and on some knives and scissors . It

2244-449: The leather pieces, for no known purpose at all other than style. The step clamp and step block assembly in metalworking adopt serration for the purpose of applying clamping pressure from an adjustable position. Humans have used serrated blades since the Mesolithic era, when prehistoric humans made these from flint . A serrated blade has a toothlike rather than a plain edge, and is used on saws and on some knives and scissors . It

2295-468: The material being cut, which cumulatively serve to cut the material along the line of the blade. Cuts made with a serrated blade are typically less smooth and precise than cuts made with a smooth blade. Serrated edges can be difficult to sharpen using a whetstone or rotary sharpener intended for straight edges but can be sharpened with ceramic or diamond coated rods. Further, they tend to stay sharper longer than similar straight edges. A serrated blade has

2346-468: The material being cut, which cumulatively serve to cut the material along the line of the blade. Cuts made with a serrated blade are typically less smooth and precise than cuts made with a smooth blade. Serrated edges can be difficult to sharpen using a whetstone or rotary sharpener intended for straight edges but can be sharpened with ceramic or diamond coated rods. Further, they tend to stay sharper longer than similar straight edges. A serrated blade has

2397-423: The material being cut. By having less contact area than a smooth blade or other edge, the applied pressure at each point of contact is greater, and the points of contact are at a sharper angle to the material being cut. This causes a cutting action that involves many small splits in the surface of the material being cut, which cumulatively serve to cut the material along the line of the blade. In nature, serration

2448-440: The material. This necessitates the blade being strong enough to resist breaking before the other material gives way. The angle at which the faces meet is important as a larger angle will make for a duller blade while making the edge stronger. A stronger edge is less likely to dull from fracture or have the edge roll out of shape. The shape of the blade is also important. A thicker blade will be heavier and stronger and stiffer than

2499-473: The skylines of mountains (the Spanish word sierra , as in the Sierra Nevada, means a saw). These occur due to the uneven action of landform edges pushing rock upwards, and the uneven action of erosion . Human uses of serration have copied, and gone beyond, those found in nature. For example, the teeth on a saw or other serrated blade serve a similar cutting or scraping purpose as the serration of an animal tooth. Tailors use pinking shears to cut cloth with

2550-442: The technique of differential hardening by covering their sword blades in different thicknesses of clay before quenching . Thinner clay allowed the heated metal to cool faster, particularly along the edge. Faster cooling resulted in a finer crystal structure, resulting in a blade with a hard edge but a more flexible body. European sword makers produced similar results using differential tempering . Blades dull with use and abuse. This

2601-508: Was done because furnaces of the time were typically able to produce only one grade or the other, and neither was well suited for more than a very limited use blade. The ability of modern steelmakers to produce very high-quality steels of various compositions has largely relegated this technique to either historical recreations or to artistic works. Acid etching and polishing blades made of different grades of steel can be used to produce decorative or artistic effects. Japanese sword makers developed

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