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Username Post: Kitchen Knife Terms / Def        (Topic#809833)
Master Member KnifeNut!
12-13-07 17:50.10 - Post#1391851    

Knife Descriptions/Properties:

Kirenaga - Refers to the duration a knife is able to retain it's sharp edge.

Urasuki - The recessed or concaved surface on the back side of a traditional Japanese single beveled knife which reduces drag against the material being cut.

Hagane & Jigane - Traditional Japanese (i.e. single beveled ) knives are made from forge welding two materials together: the Hagane and the Jigane. The Hagane is the hard steel which forms the cutting edge. The Jigane is the mild steel or soft iron which supports the Hagane (hard steel), and provides flexibility and ease of sharpening.

Kasumi - Craftsmen forge kasumi knives by joining the soft Jigane to the harder hagane. After forging, hammering, and shaping, the Hagane becomes the cutting edge of the single-edged blade. Kasumi knives are generally right handed. The main feature of the right side of the blade is the front bevel or ‘shinogi’ (blade road). The left side or back of the blade consists of the ‘urasuki’,

Kasumi knives are much easier to use and quicker to sharpen than honyaki knives; but their kirenaga is shorter. Kasumi means "mist," which refers to the hazy appearance of the soft iron part of the blade in contrast to the glossy appearance of the carbon steel cutting edge

Hon-Kasumi - Refers to a high-grade kasumi knife. They are often made of higher quality materials and special attention is paid in their forging, tempering, and finishing processes. More work is accomplished on a hon-kasumi knife by hand than is so with a standard kasumi knife.

Warikomi or San Mai - Refers to a knife that differs from kasumi knives in that they are double-edged. The soft Jigane laminates both sides of the Hagane core, to support the hard cutting edge and provide ease of sharpening.

Honyaki - Translated means "true-forged". Honyaki knives are constructed entirely out of one material, usually high-carbon steel. They are difficult to forge and shape so they are often expensive. Honyaki knives have the greatest kirenaga of Japanese knives. However, because the steel in this style of knife is hard throughout the blade, they are quite easy to chip, crack, or break if used improperly. Also, because the entire blade is hardened steel, sharpening them becomes a real challenge. Craftsmen require a great amount of skill to forge honyaki knives and chefs need a lot of experience to use and care for them.

Mizu-honyaki - Most honyaki kitchen knives are known as mizu-honyaki, a subset of honyaki knives that are differentially hardened in water. Differentially hardened honyaki knives may be hardened in oil, but the specification ‘mizu’ designates water.
The blacksmith applies mud thicker on the body of the blade and thinner towards the edge. The mud is allowed to dry. The blade is then heated to a specific temperature, and quenched in water. The edge cools faster than the core of the blade, and thus the blade is differentially hardened resulting in a hamon line. The edge is extremely hard, while the body (primarily the spine) of the blade is softer and flexible.

Hamon - The line which marks the differential hardening of a mizu-honyaki blade. Typically this line is wavy.

Hocho - The Japanese term for knife.

Kitaeji – refers to multiple-layered jigane, sometimes referred to as 'damascus'.

Suminagashi - refers to the appearance of the kitaeji pattern. Sometimes described as ‘damascus’, suminagashi refers to multiple layered jigane. Suminagashi is a technique of dipping drawing paper in water that has ink floating on it. The term is used to describe the pattern of the forge welded jigane.

Mokume - refers to a ‘wood grain’ pattern observed in layered jigane for traditional Japanese knives. It also refers to pattern welded non-ferrous metals used in decorative elements, i.e. bolsters, endcaps, for Western-style knives.

Migaki - A polishing effect that involves a mirror-like, glossy finish. In the context of kasumi or warikomi, migaki refers to a brightly polished jigane.

Kurouchi - Traditional of rural Japanese cutlery. The warikomi blades are unfinished except for the edge, and retain the blue-black patina from the forge.

Japanese Knife Styles:

Hōchō 包丁 - Japanese Kitchen Knife Types

Wa bōchō (和包丁) Traditional Japanese Knives

(kataba edge unless otherwise noted)

Sashimi bōchō (刺身包丁) sashimi knife
Yanagiba (柳刃) willow blade - designed solely for slicing raw fish. This common/pointed willow leaf design originated in Osaka (Kansai region).
     Kensaki Yanagi (剣先柳刃, けんさき) sword tip Yanagiba

Usubiki (うす引) thin slicer, Yanagiba shape but thinner blade

Fugubiki (ふぐ引,フグ引) fugu (blowfish) slicer - thinner and slimmer than Yanagiba.

Takobiki (蛸引,たこ引,タコ引) A square tipped yanagi style knife that originated in Tokyo (Kanto region). The blade usually has very little curve to it and is narrower than the common yanagi. It was designed for cutting tako (octopus
     Sakimaru Takobiki (先丸蛸引,先丸タコ引) round tip Takobiki
     Kiritsukegata Takobiki (切付型タコ引) sword tip Takobiki[/list]

Deba bōchō (出刃包丁) pointed carving knife, kitchen cleaver for fish
Deba (出刃), Hon Deba (本出刃) pointed carving knife - A heavy thick bladed knife used in fish butchery. It is primarily for decapitation and filleting. Debas' can also be used for poultry butchery but are not recommended for cutting bones.

Mioroshi Deba (身卸出刃, 身おろし出刃) Oroshi Deba (卸出刃) Wholesale knife, thinner, longer, sleeker blade for filleting, trimming and portioning fish

Aideba (相出刃) like Mioroshi Deba but smaller bevel angle than Mioroshi Deba

Ajideba (鯵出刃) Kodeba (小出刃) deba for de-boneing horse mackerel (aji) and small sea bream, grating, and filleting - shorter blade (typically 90 to 135mm)

Sakekiri (鮭切り包丁) Sake Deba bōchō (鮭出刃包丁) Salmon knife, thinner and wider blade, similar to Funayuki

Usuba bōchō (薄刃包丁) thin blade, vegetable knife - A usuba has very little if almost no curve to the blade. It is capable of one of the sharpest most delicate edges and is used only for fine vegetable work. There are several variants of this style of knife with all performing the same task for the most part:
Usuba/Azumagata usuba (薄刃/東型薄刃) Kanto style usuba

Kamagata usuba (鎌形薄刃) Kansai style usuba, scythe shaped

Ryōgata/Hishigata usuba (菱型薄刃) pointy style usuba, diamond shape tipped

Mukimono (むき物,ムキモノ) Kanto style paring knife, shape similar to Ryōgata usuba but slimmer and thinner

Mentori bōchō (面取り包丁) Kansai style paring knife, shape similar to Kamagata usuba, but smaller and thinner kataba or ryoba edge

Special kitchen knife (特殊包丁)
Magurokiri bōchō (鮪切り包丁, マグロ切包丁) Tuna filleting knife

Kiritsuke (切付, 切りつけ) Kanto style multi purpose knife, diamond shaped tip

Hamokiri bōchō (鱧切り包丁), Honekiri (骨切) pike eel knife

Sushikiri bōchō (寿司切包丁) sushi roll knife, special knife to cut sushi rolls, ryoba edge

Funayuki bōchō (舟行包丁) knife to cut fish and vegetables, like thin Mioroshi Deba. Also used by some makers to describe a thin, double bevel knife somewhat similar in profile to a gyuto.

Kaisaki bōchō (貝さき包丁) Baran-kiri (バラン切) parer for shellfish

Wa Gyutō (和牛刀) Japanese Cattle sword

Menkiri bōchō (めん切り包丁, 麺切り包丁), Sobakiri bōchō (そば切り包丁) Buckwheat noodle knife

Udonkiri (うどん切り) Noodle knife - Heavy large wide blade knife for cutting fresh udon noodles.

Kashigiri (菓子切り) Candy knife

Tuke bōchō (付包丁) Knife for steamed fishcake

Suikakiri (スイカ切) Watermelon knife

Kabochakiri (カボチャ切) Pumpkin knife

Saiku (細工) finely decorating knife

Unagi saki bōchō (鰻サキ包丁) eel knife
Kantōgata unagi saki (関東型鰻サキ) Kanto style eel knife
Kyōgata unagi saki (京型鰻サキ) Kyoto style eel knife
Osakagata unagi saki (大阪型鰻サキ) Osaka style eel knife
Nagoyagata unagi saki (名古屋型鰻サキ) Nagoya style eel knife

Home Kitchen Knives (家庭用包丁)
Nakiri bōchō (菜切り包丁) vegetable knife, ryoba edge - A square tipped super thin bladed vegetable knife. Looks like a small cleaver but only used for delicate vegetable work.

Santoku (三徳庖丁) three virtue kitchen knife, ryoba edge - All purpose knife designed for home use. Has a short blade (150-190mm) and a rounded only slightly pointed tip.

Kawamuki bōchō (皮むき包丁) Kansai type peeling knife, shape similar to Kamagata usuba but much smaller, thin blade, kataba or ryoba edge

Kurimuki (くりむき) Kanto style Chestnut Peeling Knife, kataba or ryoba edge

Yō bōchō (洋包丁) Western Style Japanese Knives

(ryoba edge)

Gyutō (牛刀) - All purpose knife. Gyuto means Cow sword as it was originally designed for butchering large sides of beef. It is the closest equivalent to a Western chefs knife but usually has a thinner blade and harder steel. Double bevel. A wa-gyuto is the same blade, but with a traditional, Japanese style handle.

Sujihiki (筋引) Slicer - Long narrow blade thin knife for slicing cooked meats. Works well on raw meats as well. It is a good substitute for a yanagi. Similar to a western slicer but usually has a thinner blade and harder steel. Double bevel

Petty knife (ペティナイフ) - The Japanese equivalent of the utility knife. Petty’s are optimal for cutting on the board rather than in the hand. They are generally distinguished by longer blade lengths, up to 150mm. The heel is often more prominent than in paring knives

Yo-Deba (洋出刃) Western style deba with a kataba style edge.

Pan kiru knife (パン切ナイフ) Bread knife

Honesuki (骨スキ) Boning Knife - Poultry boning knife for chickens and smaller birds. Double bevel but usually heavy bias to the right. Comes with western or traditional handle.
     Honesuki - Kaku 骨スキ(角)
     Honesuki - Maru 骨スキ(丸) hankotsu

Garasuki (ガラスキ) Poultry Butchering Knife developed in the poultry houses of Japan. Typically the edge is only ground on the front while the back is flat or hollow. Essentially a larger version of a honesuki.

Chuckabocho - The Japanese version of a Chinese cleaver made with harder steel and usually is better finished. Double bevel. Comes with western or traditional handle.

Hankotsu - A Japanese butchers knife made for hanging style butchery and breaking down of large animals.

Western deba - Heavy chef knife for fish and meat butchery, and chopping hard vegetables. Comes with western handle. Double bevel.

Western Knife Styles:

Chef’s knife - Chef’s knives are the most versatile and commonly used of knives. Chef’s knives can be used for a wide range of cutting tasks. The blade ranges in length from 6" to 14".

-German-style chef’s knives are characterized by a greater curvature, described as ‘belly’, along the edge. These are optimal for a rocking cut.

-French-style chef’s knives are narrow in profile compared to German knives. The belly is less pronounced, and the blade is often thinner.

Paring knives - Parers are small knives with blade length varying from 2" to 4". Paring knives are designed to cut items such as fruit in the hand.

-Spear point parers are the most common and versatile of all paring knives. The profile is a reduced version of a chef’s knife.

-Sheep's foot parer - Also known as a stylet. The sheep's foot parer has a blunt tip and straight-edged blade which maximises contact with the food being cut.

-Fluting knives provide the greatest control of the tip of all paring knives. Fluting knives are a superior garnishing tool when intricate cuts are required.

-Tourne or Bird’s Beak - A tourne has a forward arching curve in the blade for working round fruits and vegetables, making it an ideal garnishing tool.

Serrated tomato knife - Has a similar profile to a utility knife. It is useful for many cooks due to the serrations, which prevent the edge from slipping when cutting soft-bodied but tough-skinned tomatoes.

Bread knives - Serrated or scalloped-edge slicers. As the name suggests, bread knives are used to cut bread and other items with a tough crust encasing a soft interior.

Boning knives - Used to separate flesh from the bones of meat and poultry.

Carver - Slicers, usually under 9", which are used exclusively to slice cooked meats. Slicers in general have long blades with a narrow profile, which reduces friction when cutting meat.

Cimetar - Used to break down primal and sub-primal cuts into portions for eating.

Skinner Have short, curved blades, generally under 6". They are used to remove the hide from a carcass.

Cleaver - A heavy knife with a square profile. The main use of Western cleavers is as a butchering tool for cutting through bones.

-Chinese cleavers are used for virtually all cutting tasks in the Chinese kitchen, assuming the role of chef’s knife. Chinese cleavers are used to cut vegetables as well as meat, unlike Western cleavers. Chinese cleavers which are used as kitchen utensils are much thinner in cross-section than Western cleavers. For butchering duties, the Chinese use a subset of heavier cleavers similar to the Western meat cleaver.

Misc. Knife Terms:
Rockwell Hardness - A measure of hardness on a scale developed by the company Rockwell. The Rockwell Scale characterizes the indention hardness of materials through the depth penetration of a hard point. Hardness is related to strength in that both are measures of the pressure that results in plastic deformation of materials. The C scale is used for steel, hence the abbreviation RC or Rockwell C.

Damascus - refers to either pattern welded steel, or the first crucible steel, which is known from ancient blades. Pattern welded steel exhibits surface patterns similar to those seen on ancient swords.

The ancient steel known as ‘damascus’, was the first crucible steel, and is commonly known today as wootz. However, the term ‘wootz’ is historically innacurate, as the term was never used to denote crucible steel. Centers for crucible steel production existed in India, Central Asia (where it was known as pulad), and also an equivalent steel (bulat) was produced in Russia.

(If anyone is interested, Ann Feuerbach is an authority on crucible damascus steel:

Granton Edge/Kullens - Small indentations that trap fluids and interrupt the compression bond or airlock that occurs when slicing food. The grantons also reduce the contact area of the blade, and thus reduce general drag.

Shapes of Chef's Knives
There are generally three accepted, basic shapes to a "chef's" knife. The German shape, the French shape, and a Japanese shape (referred to as a gyuto). The following illustration shows the differences in the blade profile of each:




Parts of Japanese & Western Knives:
The above terms are best defined by using the following illustration:

Bolster - Best described using the following diagram of a Western style chef's knife. The diagram represents a chef's knife with a full bolster. Many Western manufactured knives have a full bolster that continues down the heel of the knife to the edge. Many feel that a full bolster makes a knife difficult enough to sharpen that they won't buy knives with them.

Knife Bevels & Edges
The following diagram respresents the most widely used types of edges put onto double bevel kitchen knives:

Below are two illustrations showing traditional, chisel ground kitchen knives.

"Need definitions for primary, secondary, etc. bevels"

Steel Terms: (The following steel information was written by Larrin Thomas)
Carbides – Simple explanation: Hard particles formed in steel when carbon forms with iron or transition metals.
In depth: Carbides control greatly the level of wear resistance and toughness in a steel. Because carbides are extremely hard, a great volume of them will make a steel very brittle, especially if the carbides are large and unevenly distributed. Steels vary from nearly 0% all the way to 30% carbide volume.

Grain size – Simple explanation: Steel is made up of grains, smaller grains means greater toughness and strength.
In depth: Smiths can vary heat treatment and forging processes to yield a finer grain size, though different steels are more easily heat treated for a finer grain size than others, this generally has to do with the alloy added, carbides “pin��? the grain boundaries and prevent them from growing. The alloys with the highest melting point prevent grain growth the best. Vanadium and Niobium (Columbium) are often added to steels for finer grain. The reasons for grain size contributing to toughness and strength would require too much space to explain here.

“In solution��? and the “matrix��? – If alloy is “in solution��? that means it is part of the steel and not currently tied up in carbides. This can also be called the “matrix��?, e.g. there is 13% chromium in the matrix.

Wear resistance – Simple explanation: The ability to resist abrasive wear.
In depth: Important when slicing, especially when slicing abrasive materials like rope and cardboard. Wear resistance is important for edge holding in many types of knives, but less important in general when it comes to kitchen knives, because edge stability, strength, and toughness are more important for holding an acute, polished edge. If a cook uses a slicing cut and the edge is thick (compared to Japanese and other thin kitchen knives), then wear resistance is beneficial. Generally greater wear resistance means it is more difficult to sharpen, so even with a knife that will benefit from a steel of greater wear resistance, less wear resistance may be preferred for easier resharpening.

Strength - Simple description: To resist deformation or rolling.
In depth: Strength is most greatly controlled by the Rockwell hardness scale, abbreviated Rc, though different steels can have different yield or tensile strength even with the same Rockwell hardness. The things that factor into this are grain size and alloy in solution. According to Takefu steel (the makers of VG-10) Cobalt strengthens the matrix of steel, regardless of Rockwell hardness. Carpenter steel offers tensile and yield strength numbers of their steels at various hardnesses and the variety of strength numbers while at the same hardness for different steels can be observed. Generally strength and toughness are opposed to each other, raising the hardness lowers toughness. Only decreasing grain size increases both strength and toughness. Higher strength means the edge can be thinner, because the edge is less prone to rolling.

Toughness - Simple explanation: Ability to resist chipping or breakage.
In depth: Toughness is controlled by amount of carbon in solution, the hardness the steel is heat treated to, the carbide size and volume, and the other alloy in solution. High amounts of chromium weaken grain boundaries (though generally carbide size and volume is the limiting factor as far as toughness in stainless steels). Nickel and silicon in moderate amounts increase toughness without effecting strength. Carbide size and volume are probably the greatest controlling factor for toughness.

Edge Stability – Simple explanation: Ability to hold a fine, acute, polished edge.
In depth: Edge stability is controlled most by carbide size and volume. The finer the carbide structure, the better a steel is at holding sharpness when sharpened very acutely and at a high polish. Evidences of a steel with low edge stability are losing initial sharpness quickly or chipping either while cutting or while sharpening with an acute bevel. The finer the edge and the finer the polish the more this will be apparent. Edge stability and toughness are often connected, but not always the same. Sometimes a steel can have high edge stability with fairly low toughness, or a steel with low edge stability can have moderate toughness. Blue Super has fairly high edge stability but low toughness; D2 has low edge stability but moderate toughness. Generally wear resistance and edge stability are opposed to each other since a greater volume of carbides means greater wear resistance but less toughness and edge stability, meaning one of the most important factors for selecting a steel are how much slicing it will be doing and how thick the edge will be. As already said, usually edge stability is more important in kitchen knives.

Types of Steel:
Powder metallurgy steels: Because high alloy, high wear resistance steels usually have low toughness and large carbide structures, powder metallurgy was developed. The steel is rapidly solidified into a powder rather than slowly cooled in a large ingot. While the carbides are much smaller, this will not turn a steel that is high in wear resistance into one that has high wear resistance and high edge stability, because the carbide volume will still be high. This process does decrease the average carbide size and grain size, and raises the toughness, corrosion resistance, and edge stability.

Simple carbon and alloy steels - Carbon steels are the simplest and easiest to understand. Adding more carbon means greater potential hardness. Steel cannot hold more than about .77% carbon in solution, all carbon after that will be held in cementite, or iron carbides. Iron carbides are the softest carbide. Varying amounts of carbon can be in solution from different heat treatments, meaning even a carbon steel with .77% C will usually have carbides after heat treatment. Generally other alloy is added to simple carbon steels simply for greater hardenability, since 1095, with no alloy, must be quenched in water and has very little time in cooling to get full hardness. Alloy makes it so that there is more time cool it, and this is where oil hardening steels come in. Manganese is the main alloy that contributes to hardenability, though chromium and molybdenum also help. Though I will refer to the carbides as “iron carbides��?, they are actually M3C carbides, M meaning metal, and could be Fe3C, or other variations, such as Cr2FeC. Most carbon steels used in kitchen knives are capable of being heat treated to very high hardnesses. Carbon steels usually have good toughness and very high edge stability because iron carbide dissolves at fairly low temperatures, below typical forging temperatures. Because the carbides dissolve at low temperatures, they are easy to break up when forging into a fine and evenly distributed structure. These steels do not vary much when it comes to corrosion resistance, all have basically not resistance to corrosion. These steels are the choice of those that forge steels, because they respond to thermal treatments quickly, do not require electronically controlled equipment, and generally move easily under the hammer. Even small alloy additions make a steel more red hard and more difficult to forge. Though alloy steels are technically a different category than simple carbon steels they are similar enough that they will be in the same section here. Any steel with anything added other than manganese and carbon are alloy steels.

1095, W1, W2, Hitachi Yellow (Shigami): These steels are all similar, essentially 1.00% C and iron, with the minimum of manganese for hardenability and (hopefully) trace impurity. W2 has .2% vanadium added for grain refinement. These steels can be heat treated very hard, and respond very well to various thermal cycles because they are very simple. They have low wear resistance compared to many other steels, only surpassing steels used by forgers for high toughness like 5160 or 1075. Toughness is moderate and edge stability is very high.

Hitachi White (Shirogami) steel: Similar to 1095 and W1 but with even more carbon (1.45%), this steel gets very hard and has a moderate amount of small iron carbides. Higher wear resistance than 1095 or W1 but does not have great wear resistance. Has fairly poor toughness but very good edge stability.

O1: A modification of 1095 with high manganese so it is oil hardening, vanadium for grain refinement, and tungsten, chromium, and tungsten added for a little greater wear resistance. There probably isn’t enough tungsten, molybdenum or chromium added for actual tungsten, molybdenum, or chromium carbides, it is most likely still iron carbide with a higher percentage of alloy, making the cementite somewhat harder. O1 gets very hard, has high edge stability and good toughness.

52100 (SUJ2): 1% C and 1.5% Cr. The chromium makes it deeper hardening though it is still technically a water hardening steel. The chromium forms with the iron carbides to make them somewhat harder, also raises the overall carbide volume for greater wear resistance. O1 and 52100 are not far off from each other when it comes to wear resistance, 52100 is a little tougher and O1 is a little more wear resistant. 52100 has extremely fine carbides and so has very high edge stability.

Hitachi Blue (Aogami) #1 and #2: The major downfall of simple carbon steels is their comparatively low wear resistance because of the lower hardness of iron carbide. These steels have high tungsten to form the much harder tungsten carbides for wear resistance. They still have good edge stability because the tungsten carbides are still easily broken up in forging. Blue #1 and #2 have greater wear resistance than any of the previous steels as well as still having good toughness and edge stability. When two steels have the same carbide size and volume but the one steel has harder carbides, the steels will have similar toughness and edge stability but the one with harder carbides will have greater wear resistance. These harder carbides do make the steel somewhat more difficult to sharpen. Blue #1 and #2 are good general purpose steels because they have greater wear resistance than most other simple carbon steels while still having the high edge stability and toughness of most carbon steels. Blue #1 and #2 have less carbon, tungsten, and extra alloy than Blue Super, though in varying amounts, Blue #1 is more wear resistant and less tough than Blue #2.

Hitachi Blue (Aogami) Super: White steel modified with some alloy for greater hardenability and high tungsten for harder carbides. The highest in wear resistance of any of the simple carbon steels generally used in kitchen knives, and also the lowest in toughness. Does have good edge stability because the carbides are little bigger than those in other steels, but is a little bit lower because they are a little bit larger and in a greater volume. Still has much better edge stability than large carbide stainless steels. This steel has one of the highest combinations of wear resistance and edge stability, properties that are generally opposed to each other, which means it is suitable for a variety of cutting tasks or types of knives. Its main disadvantages are low toughness and of course no corrosion resistance.

Air hardening tool steels: Sometimes air hardening tool steels and simple carbon steels are grouped in the same category, but they are quite different. To be air hardening a large amount of chromium is added. True air hardening steels also have 1.00% Molybdenum added though steels can be successfully hardened in thin sections (such as a knife) without it. Air hardening is preferable, especially in industry, because they can be hardened without an oil or water quench. Because the quench is low in severity, cracking in quenching is not an issue either. Generally iron carbides are not formed in air hardening steels and the base carbide formed is chromium carbides. As with iron carbides, they are not usually pure chromium carbides, but are either M7C3 or M23C6. Chromium carbides are harder than iron carbides, but not as hard as tungsten or vanadium carbides (both MC carbides). Steels are initially cast in a large ingot and are heavily segregated, even simple carbon steels, the structures are refined through forging. Air hardening tool steels generally have lower edge stability than simple carbon or alloy steels because chromium carbides dissolve at higher temperatures, and these steels often have a greater volume of carbide. When the steels have a fairly low volume of carbide, it is manageable enough to still have a fine carbide structure if properly forged, examples are A2 or stainless steel 13C26. Air hardening steels have a certain amount of corrosion resistance because of the added chromium and molybdenum.

A2: A2 has 1.00% C with 5.25% Cr, and around 1.00% Molybdenum and .25% vanadium. A2 has a fairly low volume of chromium carbides for greater wear resistance than most simple carbon steels, but still has moderate to high wear resistance and high edge stability. A2 isn’t generally heat treated a very high hardness, with 61-62 Rc being about as hard as it is ever heat treated to.

SKD-11 / D2: D2 has high carbon (1.5%) and chromium (11-13%) with just under 1% of molybdenum and vanadium. D2 has a large volume of large carbides. It has very high wear resistance, low edge stability and moderate toughness. Also generally heat treated no harder than 62 Rc. D2 is often advertised as a “semi-stainless��? steel. Though it has 11-13% chromium, only 7% or less is in solution after heat treatment because so much chromium is taken up in carbides from the large amount of carbon. It probably has the highest corrosion resistance of the air hardening grades.

3V: 3V is a powder metallurgy steel that is designed to have very high toughness with moderate wear resistance. It has a similar carbide volume to A2 but the carbide structure is slightly smaller and more evenly distributed because it is a PM steel, also it forms only vanadium carbides for greater wear resistance. Though advertised as having greater wear resistance than D2, it is more realistically somewhat better than A2. It has edge stability. Generally not heat treated harder than 62 Rc.

10V: A PM steel with a similar carbide volume to D2 but much smaller and evenly distributed and has even greater wear resistance because it forms all vanadium carbides. Some makers heat treat it as high as 64 Rc. Toughness and edge stability slightly greater than D2 with extremely high wear resistance.

High Speed Steels: Air hardening steels that have a high amount of molybdenum and/or tungsten added for red hardness. Red hardness is not required for knives but there are a couple high speed steels used with knives. Because of the extreme amount of alloy these steels usually have a fine grain size, especially when heat treated in the ranges used for knives as opposed to when heat treated for maximum red hardness. High speed steels usually have a certain amount of corrosion resistance because of the added chromium and molybdenum.

M2: The base high speed steel that has a surprisingly fine carbide structure for good edge stability, toughness is also good. M2, like most high speed steels, is capable of very high hardness, 66 Rc or so. Wear resistance is very high.

CPM-M4: A PM version of M4 that has similar or better edge stability than M2, greater toughness, and even greater wear resistance and potential hardness. M4 has 4% vanadium instead of the 2% in M2.

Stainless steels: Similar to air hardening steels, but even more chromium is added for stain resistance. Though many say that “13% chromium is required to be stainless��?, in reality only the amount of chromium in solution after heat treatment is important. 440C, with 16-18% chromium only has around 12% chromium in solution after heat treatment, which is little different than 13C26 which only has 13% chromium. The difference is the amount of carbon in the steel which takes up chromium in carbides. To design a stainless steel is to balance the amount of carbon and chromium to have sufficient carbide volume, carbon in solution for hardness, and chromium in solution for corrosion resistance. These stainless steels do vary some in corrosion resistance, but won’t be ranked, most of these high carbon stainless steels are not particularly suited for the dishwasher, though can be used without detriment.

13C26/AEB-L: These are two steels made by competing Swedish companies and was designed in the early 1900s for razor blades. As you can imagine, being developed for razor blades means it has very high edge stability. The carbide structure is very fine, matching the size of even the finest carbon steels. The wear resistance isn’t impressive compared to other stainless steels, but still exceeds most carbon steels other than the Blue series, these steels have similar wear resistance to A2. 13C26 has the highest wear resistance of any stainless that has excellent edge stability. They are capable of being heat treated to 63-65 Rc. The toughness is high.

440C: Has moderate wear resistance, low toughness and low edge stability. Brittle when heat treated harder than 58-59 Rc.

ATS-34/154CM: The same steel, one made by Crucible, one made by Hitachi. Has moderate to high wear resistance, moderately low toughness, and low edge stability. Can be heat treated fairly hard, but because of toughness issues generally not taken harder than 61-62 Rc.

CPM-154: A PM version of 154CM, so it has somewhat greater edge stability, toughness, potential hardness, and corrosion resistance.

BG-42: A super-clean variation of 154CM for the aerospace industry, with a little more carbon and 1.25% vanadium added for greater wear resistance and even lower toughness and edge stability.

420/440A: Fairly different steels, but similar properties, both have a low potential hardness, but high edge stability, toughness, and corrosion resistance.

420HC/12C27M: Between 420 and 13C26, capable of 58-60 Rc, with high edge stability and toughness.

12C27: Between 12C27M and 13C26, sacrifices some hardness and wear resistance from 13C26 for greater toughness and corrosion resistance.

19C27/VG-1: Wear resistance close to 440C but with greater edge stability and toughness than 440C and 154 CM. Corrosion resistances is fairly low compared to other stainless steels. Has “good" edge stability. Capable of 65 Rc, probably shouldn’t be heat treated higher than 62-63 Rc. Composition = C - 0.95 to 1.05, Cr - 13.0 to 15.0, Mo - 0.2 to 0.4, Ni - 0.25 or lower.

VG-10: Wear resistance higher than VG-1 but not as good as 154CM, with toughness and edge stability greater than 154CM but not as good as VG-1, so it has good to moderately low edge stability. Has greater corrosion resistance than VG-1. Usually not heat treated higher than 60-62 Rc. Compositon = C - 1.0, Cr - 15.0, Mo - 1.0, V - 0.2, Co - 1.5

S30V: A PM grade that has very high wear resistance, higher than any of the previous grades listed, with greater edge stability than 154CM, but probably lower than VG-10. Good toughness, and can be used up to 62 Rc. Also has very good corrosion resistance. Has high enough wear resistance that it can be difficult to sharpen using waterstones, due in part to the vanadium carbide. Difficult to finish for a knifemaker.

SG2: A PM grade that is a variation on S30V, is capable of slightly greater hardness but otherwise has similar properties, a little lower in wear resistance and a little easier to sharpen.

S90V: A PM grade with even greater wear resistance than S30V, but has lower toughness, edge stability, and potential hardness, usually not heat treated above 58-60 Rc. Very difficult to sharpen, and very difficult to polish for a knifemaker.

ZDP-189/ Cowry-X: These two steels are very close, both PM steels with the odd composition of 3% C and 20% Cr, along with .5-1% molybdenum; one has a small amount of tungsten while the other has a small amount of vanadium. Has wear resistance to match S90V, with very low toughness and edge stability. The most interesting part of this steel is that it can be heat treated to extreme hardness, which is rare for a stainless steel. ZDP-189 is difficult to sharpen like the other high wear resistance steels. It has fairly low corrosion resistance.

The following are a series of micrographs of some of the steels discussed above:

White Steel:





Blue Super:











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Edited by watercrawl on 01-27-10 03:26.08. Reason for edit: No reason given.

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