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Knife Blade Facts (Read Before Next Knife Purchase)
Below are some common high carbon steels used for knife blades:
A-2 and 0-1 Are tool steels with very high carbon content. They offer
excellent edge holding and these alloys must have frequent maintenance
to prevent rust.
D-2 is a high carbon tool steel that has a high chromium content. It has
better stain and rust resistance than A-2 and 0-1. One of the finest steels
made for edge retention.
Damascus Steel Is simply a high carbon steel that takes on a layered
appearance, because of certain methods used during the manufacturing
process. It is attractive, tough, flexible and holds an edge well.
Stainless Steels:
420 Lower carbon content than the 440 series makes this steel very soft,
and it doesn't hold an edge well. Normally used for cheaper knives.
440A - 440B - 440C All three resist rust well, with 440A being the most
resistant and 440C the least. If your knife is marked with just 440, it is
probably the less expensive 440A. In general the 440A is just good enough
for everyday use, 440B is a solid performer and 440C being excellent.
425M and 12C27 Both of these are very similar to 440A. 425M is used by
Buck Knives. 12C27 is a Scandanavian steel.
AUS-6 Japanese stainless steel, roughly compared to 440A.
AUS-8 Japanese stainless steel, roughly compared to 440B.
AUS-10 Japanese stainless steel, roughly compared to 440C.
GIN-1 A steel with slightly less carbon, a little more chromium, and alot
less moly than ATS-34. Used by Spyderco, a very good stainless steel.
ATS-34 Very high carbon content, giving it a very good edge retention.
154-CM Very similiar to ATS-34, premier high quality stainless, it isn't
manufactured much anymore.
ATS-55 Similiar to ATS-34, but without the moly and some other elements
added. Looks like the attempt to get the ATS-34 edge with increased
toughness. Spyderco is using this steel also.
BG-42 Similiar to the ATS-34, with two major differences. It has twice the
amount of manganese and has vanadium added. These additives make an
even better edge holding.
CPM T440V and CPM T420V Two steels that hold an edge better than
ATS-34, but difficult to get the edge there. Don't expect the toughness
of ATS-34.
Non-Steel knife blades
Cobalt - Stellite 6K A flexible material with wear resistance, is practically
corrosion resistant. Stellite 6K, sometimes seen in knives, is a cobalt alloy.
Titanium Is extremely rust resistant and is non-magnetic. Popular as
expensive used as dive knives with the Navy Seals.
Ceramics Numerous knives have been offered with ceramic blades. Usually,
those blades are very brittle, and can not be sharpened by the user. They do
hold an edge well and Boker and Kyocera make some knives with this material.
Boning Knife This type of knife generally has a blade of five to
six-and-one-half inches in length, and features a very thin blade. You'll
want a fairly stiff boning knife for boning big game, but a very flexible
boning knife is preferred for turkey or upland birds.
Fillet Knife Similar to a Boning Knife, these thin blades are
six-and-one-half to nine inches in length and should be quite flexible. Fillet
knives are ideal for removing a fishes meat from the bone in one piece and can
do double duty for dressing birds as well.
Skinning Knife These specialty designs are created to simplify the
delicate task of removing an animal's hide without nicking the skin. Blades
are generally short with a deep drop to limit the area of impact and work
in tight areas when caping an animal. Some skinning knives are designed
with T-handles for slip-free use and a more comfortable grip.
Slicing Knife This design has a very narrow, thinblade, usually eight
to twelve inches in overall length, and is very effective when cutting very
thin slices of meats for jerky. The more flexible it is, the easier it will be to
get a thin slice. Specialty slicers have a curving or scimitar-style tip to assist
in tight spots, like between wing and breast of birds. For applications such as
preparing sushi, slicing knives are sharpened on only one side, to lessen
resistance on the flat side, which produces a thinner slice.
Utility Knife This all-purpose knife is usually about six inches in overall length,
but can be as long as nine inches. As its name implies, it's an all-round useful blade
that will do some jobs better than others.
Serrated Blades Serrated blades could be considered a "semi-saw," providing a
more aggressive cutting surface. Although they produce "unrefined" cuts, serrated
blades retain their ability to cut long after straight blades have lost their edge.
Caping Knife This style of knife needs to be lightweight and comfortable
to hold for extended periods while doing fine detail work. Cutting around
a trophy's ears, eyes and nose is a delicate process requiring precise work,
control and a very sharp edge.
Cleaver Broad, thick blades distinguish this knife. Its hefty weight
makes quick work of cutting through bone, cutting tough gristle and
splitting ribs. Cleavers have a thick edge that will not chip easily. You
want a heavy cleaver. The heavier its weight, the easier it is to use and
control.
Knife Parts
Bolster - An integral part of most good knives, it is a thick piece of metal between
the handle and the blade, made to add weight to the knife, provide it with better
balance and a comfortable resting place for the hand. It is sometimes called the
shank.
Tang This is the part of the blade that runs from the bolster back into the handle.
The best knives have a full tang, and, except for some of the sealed-handled knives,
it is visible on the top, back and bottom of the handle, held securely by multiple
rivets. A half tang is the next preference, visible on top and back of the handle, but
not on the bottom.
Handle Usually made of wood, graphite fibers, plastic, bone, metal or
a combination of these materials, the handle envelops the tang, and is
usually fastened by rivets or encased in the plastic or metal.
Wood offers an excellent grip but requires regular care; keep it out of water
and rub occasionally with mineral oil.
Plastic may become somewhat brittle in time, and can be slippery in the hand
without a grip surface. Plastic-impregnated wood has properties similar to wood,
but requires less care and lasts longer.
Some of the new man-made materials, such as Kraton, Micarta or Polyamide offer
an excellent grip and comfort, plus they will virtually last forever.
Metal is fairly indestructible when use for handle material, adds extra heft, and can
be slippery or firm; try them first. And every manufacturer sports differing sizes and
ergonomic designs. A handle that is perpendicular to the blade can be very
comfortably used to overcome physical impairments.
Spine Opposite the sharp edge, the back, or spine, is thick on most good knives,
except for carvers and slicers, to provide strength to the blade. It can also be used to
scrape the cutting board after cutting. Note that, on forged knives, it tapers from the
bolster to the tip.
Flat This is the wide, flat part of the knife. It can be fully tapered from the back
down to the edge, a quality usually found in better knives. In lesser quality knives,
it is hollow-ground to form a distinct inward curve toward the edge.
Tip One third of a blade's tapered end is considered the tip.
Point At the tip of the knife, the point should be sharp and relatively thin. It is used,
in many knives, for incisions, for cutting small delicate items and for carving.
Edge The working part of the blade, from point to heel. This sharp part is either flat
ground, hollow ground or serrated. In better non-serrated knives you'll find mostly
flat ground edges, though a few still sport hollow ground ones with their thinner blade
easier to keep sharp. A good edge is made through a three-step process, ground at
three different angles to give them a sharper, longer-lasting edge.
Gut Hook This is a particularly handy feature when field dressing game. A special
round hone is required to keep this area of the knife properly sharpened.
Pommel The pommel or butt end of a fixed blade knife handle is generally finished
with a butt cap made of metal, stag horn or plastic.
Blade Material
Blades are made of a wide variety of materials and each has an inherent set of
properties that makes it desirable. Like all things in life, there is an upside and a
downside to every material. Alloy steels have been enhanced with other elements
such as chromium, molybdenum, vanadium or nickel. Vanadium is added to steel to
improve hardenability and give it a fine grain, which is an important factor in wear
resistance. Molybdenum is added to improve hardenability, tensile strength and
corrosion resistance, particularly pitting. Nickel is added to improve steel's
toughness, hardenability and corrosion resistance, as well, and is often used in
saltwater diving knives. Chromium is a major element in stainless steel. Stainless steel
is excellent if you want a blade that doesn't discolor, but it doesn't hold an edge very
well. Ceramic blades are phenomenal when it comes to sharpness, but drop them on
a hard floor or rock and this brittle blade will shatter. Here is a breakdown of the most
common materials that you will encounter in shopping for the perfect blade.
High-Carbon Steel holds an excellent edge and is easy to sharpen. This grade of
metal is also called Cutlery Steel, and although you can still find these high-quality
knives, high-carbon steel is no longer widely available. Carbon is an element present
in all steel, since steel is essentially made of iron and carbon. An increase in the carbon
content of steel increases its hardness. The down side to high-carbon steel is that it is
somewhat brittle, and has a tendency to rust if not dried thoroughly. For anyone who
appreciates a really sharp blade, taking care not to drop it and wiping off moisture is
a fair compromise. This grade of steel also has a high reaction to both acids and alkalis,
which causes it to discolor. The discoloration doesn't affect its performance and to
many this patina is attractive.
Stainless Steel Keep in mind that stainless is somewhat of a misnomer for the
knife industry. The only stainless steel that absolutely will not stain is used in high
quality sinks, restaurant or hospital fixtures. Any stainless steel that will hold an edge
should be more correctly referred to as "stain less."
This alloy is so hard that it is a real chore to sharpen once the blade loses it edge.
Initially, stainless steel blades are very sharp, and they will retain that sharpness longer,
but once it loses its edge it will more than likely find its way into a drawer where it will
stay for a long time. Although recent advances in technology have produced some
never-need-sharpening knives that will hold their edge for many years, knives in this
class almost always lack the quality, balance and feel of good tools. Their lack of
intensive maintenance makes them very appealing to some people, who don't want to
deal with a whetstone or sharpener.
High-Carbon Stainless Steel The rust and stain resistant properties of this alloy
have made it the most popular of metals for knife construction. It does not hold an edge
quite as well as pure high-carbon steel and is not as easy to sharpen. While the
high-carbon properties of this alloy mitigate the shortcomings of stainless steel, when
it comes to edge quality, the ease of care makes it popular.
Titanium Better quality titanium knives are made with a sintering process on a matrix
of titanium (Ti) and a combination of carbides, using powder metal technology instead of
metal casting. This sintering process smelts the elements and reconstitutes them under
intense pressure and heat. The carbide properties in this high-tech alloy allow the blades
to be heat-treated to cutlery-grade hardness. Titanium blades are very lightweight,
durable, and retain their sharpness longer than steel. Once a titanium blade loses its edge,
it is relatively easy to sharpen. Keep in mind that titanium coated, or knives with titanium
edges, do not have the same quality as those that are made exclusively of titanium or
titanium and alloys. Since sharpening removes metal, generally speaking, titanium coated
blades and have a shorter useful lifespan.
Ceramic Zirconium oxide, aluminum oxide and other ceramics, in the form of pellets,
are melted to form this very hard, very dense space-age material that is stronger than
steel, but far more brittle. The up side is that ceramic blades hold an uncommon edge.
This material can also be manufactured into blades that are remarkably thinner than steel,
which makes cutting considerably easier since you are pushing less bulk. In balance to its
brittleness, the edge can last significantly longer with proper care. Ceramic knives are best
used for slicing, and should never be used for chopping. Unlike steel, the hardness of ceramic
blades makes them impervious to chemical reaction with either acidic or alkaline foods.
Another excellent property of ceramic blades is their weight, or lack of it. Ceramic blades
are not as fragile as one might expect, with all of this talk about brittleness, nevertheless
care should be taken not to drop them. Diamond hones are used for sharpening and repairs
to chips.
Construction Various methods are used to form a knife blade and all will have varying
qualities, dependent upon the process that was used to create it. Ductility is a term that
refers to a blade's ability to deform or bend without breaking. Tensile strength refers to a
blade's ability to resist breaking. Ultimate Tensile Strength (UTS) is the maximum load per
square inch a blade can sustain before breaking.
A blade's hardness is an indicator of how well it will hold an edge, and you will often see
a reference to the Rockwell scale. A blade's hardness is determined by using a Rockwell
machine that forces a small penetrator into the metal's surface. The depth of penetration
is correlated to an A, B, or C scale reading, called the Rockwell scales. A higher number
is assigned to harder steel that allows less penetration. Blade steels are measured on the
"C" scale and range from Rc 55 - 60. In comparison, a diamond will range in the 80's on
the Rockwell "C" scale (Rc).
You will also encounter a number of designations that indicate the type of steel used to
make a knife. While not an exhaustive listing, here are a few of the types and the reason
behind their nomenclature. D2 is a common steel used for knife blades. The D designates
Damascus steel. This is a high-carbon, high-chrome tool steel that will take and retain a
really good edge in its better refinements. Keep in mind that the name Damascus only
indicates a process and not a quality, which varies widely from one manufacturer to
another.
Stainless steel bears a number of industry designations, generally with a number such
as 154 or 420, followed by alpha characters like CM or HC. The numerical value
indicates the amount of each element used and the letters reveal the alloys that were
used. 154CM is a high-carbon, high-alloy, stainless steel made with 1.05% Carbon, 0.5%
Manganese, 0.4 - 0.55% Molybdenum and 14.0% Chromium. Therefore, the 154 indicates
one percent Carbon, .5 percent Manganese, and .4% Molybdenum, and the CM indicates
Chromium. This grade of steel is widely used by top specialty knife makers.
Forged This is a process in which metal is treated, in various steps, to enhance its
hardness, density and flexibility. A prominent bolster between handle and blade will
usually identify a forged knife, although a few forged knives are made without a bolster.
Forged knives are often heavier and better balanced. They are easier to keep sharp, and,
with care, can last for generations.
Stamped As the term implies, these knives are cut or stamped out from flat metal stock.
They do not undergo the numerous steps associated with forging and are thus lighter in
weight, are usually not as well balanced. Since the metal is not as dense as a forged knife,
they won't hold their edge as well. However, stamped knives with a high carbon content
are usually easier to sharpen and to keep sharp than less expensive knives made of
stainless steel with high chromium content.
Other Ceramics and some metals are sintered, that is, melted separately and mixed
together to form a stronger alloy or component. Some forged knives have parts that are
manufactured separately and sintered together to form a knife of good quality at a lower
cost than forged knives, and which blades perform just as well as fully forged blades.
Sometimes the weight and handling of a particular knife outweigh the importance of other
considerations and make a stamped knife a better choice in a knife. For most applications,
forged knives are recommended, especially chef knives and straight edge slicers; perhaps
complemented by some stamped metal knives such as steak knives and other serrated
edge knives, as well as a spare paring knife or two. Ceramic knives are recommended for
delicate slicing and cutting tasks, and titanium knives for those who desire a good quality
all-purpose lightweight knife.
Sintering is an innovative process developed to cause metallic powder to form a coherent
mass by heating without melting. Sintered titanium blades are crafted by fusing titanium
powder and extremely hard carbide materials into one uniform blank of metal that boasts
all the durability, flexibility and light weight of titanium plus the incredible edge retention
of ceramic materials. Unlike ceramic blades, titanium knives can be resharpened with
standard sharpening stones. With titanium blades, the really good news is that you won't
have to hone them very often. In independent testing, some titanium blades have been
shown to retain their edge five times longer than traditional high-carbon steel.
Coating blades is another new process that is gaining popularity. Various processes coat
blade steel, with compounds such as titanium-boron, zirconium nitrate, TeflonŽ and
others. Coatings achieve a number of objectives. In the case of Teflon, the coated blade
is slicker and cuts easier because of reduced friction. Other metal coatings add to the
Rockwell hardness of a blade, but many are strictly for cosmetic purposes. Beyond their
increased functionality, coated blades have more eye appeal. When buying a knife, you'll
have to decide how much functionality you want included with the form.
Grinds The grinding process determines the blade's edge and usefulness. Today, most grinding is achieved by using robotics, which is more accurate
and consistent than traditional hand grinding. This diagram illustrates the four
most common grinds used for knife blades.
The grind of your blade will determine how it is sharpened, and the angle that must be
maintained when honing.
Many of the steels used in modern knife blades are too hard to sharpen with conventional
whetstones. To hone blades with a Rockwell of 45 or higher, diamond impregnated steel
"stones" are required. Multiple layers of micron-sized diamonds bonded in nickel to a flat
metal surface make up the best stones to sharpen today's hard steel blades such as 420HC
and others. Diamond impregnated steel can even sharpen ceramic blades.
The old adage that mandates a sharp knife is safer is true, because it requires less effort to
attain the desired effect. Accidents can occur with dull knives because of the extra effort
that it takes to push the blade through hide or sinew. Knife edges should be regularly
touched up using a sharpening steel, or similar tool, to maintain the edge. Learning to
maintain your new knife should be high on your priority list because anything that has
been sharpened will eventually become dull, even a keen wit.
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