Knife Encyclopedia
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Blade shapes
- Clip Point
A blade format where the top of the blade has a cut-out -- or "clip" -- at the top of the blade. The cutout is either concave or straight. Clipping the blade brings the point of the knife lower, for control; it also makes the tip sharper. Since the sharp point is one of the goals of this format, you will often see the clip accompanied by a false edge. This format is also often accompanied by a good-sized curving belly, for slicing ability. The combination of a controllable, sharp point and plenty of belly makes the clip point an excellent all-around format, and is used on such widely-differing knives as hunters, military knives, utility knives, and bowies.
- Drop Point
A drop-point blade is characterized by a slow convex-curved drop in the point. The classic Loveless-style hunter is a drop-point pattern. The drop-point format lowers the point for control, but leaves the point extremely strong. Usually coupled with plenty of belly for slicing, this format is often used for hunting knives. This is also an extremely good all-around format, and like the clip-point, the drop-point is seen in a wide range of knives from hunters to military knives to utility knives and beyond.
- Tanto
The classic Japanese tanto shape has the point exactly inline with the spine of the blade, and has a graceful belly curve. Most tantos seen on the American cutlery market are the Americanized-tantos formats. Like the Japanese tanto, the Americanized tanto has a high-point in-line with the spine. A flat grind is applied to the point, leaving it very thick and massively strong. The front edge meets the bottom edge at an obtuse angle, rather than curving to meet it as in the Japanese tanto. There is a separate grind applied to the bottom edge, often a hollow grind to leave this edge extremely sharp. Other tanto formats have become popular also, and modifications such as clipping the point or applying a chisel-grind are often seen.
- Sheepsfoot
A format in which the spine of the blade curves down to meet the edge. This format has no point, and very little or no belly. It is used in applications where slicing is the main requirement, and a point is either not needed or would actively get in the way. For example, emergency rescue blades are of this format, and the lack of a point prevents a rescuer from accidently poking a victim who is being cut out of a seat belt. Mariner knives are usually this format as well.
- Trailing Point
A trailing point blade has the point higher than the spine, and a lot of curving belly. Most popular on skinning knives, this format leaves the point high and out of the way, while providing an abundant belly for slicing jobs.
- Hookblade
Hookblades have long been popular as gardening knives, and have recently undergone a resurgence in the tactical market as well. The format forces the material towards the sweet spot of the curve, where a lot of slicing power is available.
Blade Grinds
- Hollow
For a hollow grind, the edge is made by two concave scoops. If done right, this leaves the edge extremely thin and sharp, for exceptionally-good slicing ability. This type of edge works best when high-performance cutting is needed. It is less suitable for chopping tasks, because the same thinness that gives the edge such great slicing performance also makes this format more prone to chipping or rolling during high-impact activities. That makes this edge especially good for chores that emphasize cutting over impact uses.
- Convex
This grind has the sides of the blade arcing down in a convex curve to the edge. The edge on this format is often very sharp, because the convex curves run all the way to the edge without a secondary bevel. It is also a strong edge format, because the thin edge thickens quickly enough to have plenty of metal behind it. The main drawback of this format is that it is extraordinarily difficult to re-sharpen. Knifemakers today tend to use a slack-belt grinder to apply this edge format. You can sharpen the edge in a normal bevelled manner, but then you'll end up with just a regular bevelled edge that thickens quickly, a format that will be strong but won't be the best cutting format.
- Flat
The flat grind is a format that combines most of the cutting ability of the hollow grind, with most of the strength of a sabre grind. Flat bevels run all the way from spine to the edge bevels. This can leave the edge thin for high-performance. However, the edge thickens linearly as it moves up, so it ends up stronger than a hollow grind. This grind is also expensive to make, as the maker is required to remove a lot of metal. The combination of cutting ability and strength makes this a great all-around grind. From kitchen knives (which require thin, hi-performance cutting edges) to kukris (which require strong, shearing edges), and all uses in between, the flat grind is often an excellent choice.
- Sabre
The sabre grind has flat edge bevels that normally start around the middle of the blade, and run to the edge bevel. The kabar and many other military knives show this grind. The emphasis on this grind is strength, as the edge is often left thick, and thickens dramatically and quickly past the edge. Cutting ability is sacrificed to some extent for durability. This is a format you'll often see on knives that will take prying, digging, and chopping abuse, such as the "sharpened prybar" type knives. This grind does show up for other uses as well, such as utility use.
- Chisel
The chisel grind is ground on one side only. One side of the blade has an edge bevel on it, the other side is completely flat. Because of this, the edge on a chisel-ground knife is usually extremely thin and sharp and cuts very well. On the downside, the asymmetrical grind causes the knife to veer off course during cutting chores; it also thickens dramatically. This format has become popular on tactical knives, often coupled with a clip-point Americanized-tanto blade.
- Scandanavian Single-Bevel
Scandanavian knives, such as the puukko, often sport a grind that looks like a sabre grind. However, there are no secondary edge bevels, which leaves the edge extremely thin and incredibly sharp. Due to the sharpness of the edge, these knives will often outcut just about anything.
Knife Anatomy
- False Edge
Many knives have bevels not just along the bottom edge of the knife, but along the top as well. When present, bevels on the top edge are referred to as a "false edge". The false edge can be either sharpened or not. Whether or not the false edge is sharp, it serves to take metal away from the point, and thus enhance penetration. But taking away metal at the point also weakens the point, so this is a compromise between penetration ability and strength.
- Belly
The belly is the curving part of the edge. Bellies enhance slicing ability, and you'll often find yourself doing much of your cutting on the belly. When the belly gets larger, design considerations often dictate that the point become less sharp, so in looking at knife designs you'll often see a trade-off of belly or point depending on how important slicing vs. penetration is.
- Bevel
Imagine the knife when it's just a rectangular stock. The knifemaker puts the bar on the grinder at an angle and starts grinding in an edge. This is a bevel -- any plane taken out of the rectangular bar, along either side. Creating the primary grind, the edge itself, and the false edge are all often done with bevels.
- Guard
The guard is a barrier between your hand and the sharp edge. It will project out of the handle, to stop forward motion of your hand. The guard can be a separate component that is soldered or pinned on the blade, or an "integral" guard can be formed by including a project on the blade blank itself. On some fighters, the guards are meant not just to protect your hand from sliding up on the blade, but also to provide protection from the opponent's blade sliding down your blade and onto your hand.
- Choil
The choil is an unsharpened section of the blade. If a guard is present, the choil will be in front of the guard on the blade itself. The choil is often used as a way to choke up on the blade for close-in work. The index finger is placed in the choil, and this close proximity to the edge allows for greater control. In addition, the choil is just in front of where the blade itself becomes part of the handle, an area often prone to breakage due to the blade-handle juncture. The choil leaves this area at full thickness and thus stronger.
- Tang (Full vs Hidden etc.)
The tang is the part of the knife where the blade stops and the handle starts. There are many different terms used to describe what kind of tang a knife has, because the strength and other characteristics of the knife depend on the tang format. A full tang knife has a tang that goes the length of the handle at full width, and you can see the tang spine itself because the handle slabs are afixed to each side. This is the strongest tang format. To save weight, the maker can taper the tang so it gets thinner as it goes back into the handle; this is appropriately enough called a tapered tang. If the tang disappears into the handle itself, it's called a hidden tang. If the tang thins out considerably once it goes into the handle, it's called a stick tang.
- Butt Cap/Pommel
The pommel refers to the end of the handle of a knife. Many knives have a metal cap over the pommel, called a butt cap. Often the pommel is interesting because of a decoration; however, there are different forms of working pommels. The classic kabar features a flat metal pommel, useful for hammering jobs such as pounding in tent pegs. Other knives have pointed metal pommels known as "bonecrusher pommels", ostensibly to hit someone during combat usage. Some of these working pommels can be uncomfortable when carried, so evaluate your needs here wisely.
- Blade Spine
The blade spine typically refers to the full thickness portion of the blade. On a single-edge flat-ground knife, blade spine always refers to the outermost back of the blade. On a classic dagger, the spine refers to the fullest-thickness part of the blade running straight down the middle. On knives with false edges, the term "spine" is used inconsistently. Technically, the spine would be the fullest thickness part of the blade where the main bevel meets the false edge bevel; however, blade spine is often used to describe the back of the blade instead, right over the false edge.
- Escutcheon
The escutcheon is a medallion, often seen on the classic-style pocket knife handles to identify the brand or model of the knife, or to distinguish between model years.
Folding Knife Lock Types
- Slip Joint
A slip joint doesn't have a lock at all. The blade has a spring acting against it, to give some resistance to opening and closing. But there is no lock proper, and a slip joint closes merely by putting pressure on the spine of the blade. This format is used on a wide variety of pocket knives, from swiss army knives to the classic stockman pattern.
- Liner Lock
A liner lock has a leaf cut out of the handle's liner. When the blade is fully open, the leaf springs open and blocks the back of the blade, preventing it from closing. The liner locks has no spring pushing against the blade, so it is characterized by incredibly smooth action. To unlock the knife you thumb the leaf out of the way, so the knife can be unlocked and closed with one hand. Due to the lack of spring pressure on the blade, the blade must be kept closed another way. The blade has a detent in it, and a small ball bearing embedded in the leaf drops into the detent when the blade is fully closed, keeping the knife from open accidently (different knives will be more or less successful in this regard, depending on the quality of the ball-detent matchup). This lock format is extremely strong when done correctly, but is difficult to do correctly.
- Lock Back
A lockback, like a slip joint, has a spring operating against the blade. When the knife is fully open, a tooth at the end of the spring drops into a cut-out in the blade. Once the tooth drops in, the blade is locked open. Pushing on a cutout on the handle spine lifts the tooth out of the cutout, allowing the knife to close. Pressure from the spring keeps the blade from accidently opening.
Finishing
- Jeweled Metal or Engine Turned
Jeweling is often found on the interior frame of folders. Round patterns in the metal reflect light with eye-catching beauty. Lightly abrading the metal creates the jeweling.
- File Work
Just as it sounds, file work is a decorative pattern usually filed into the metal of a knife by the maker. Typical places for filework are on the blade spine, and perhaps on the locking bar of a lockback folder.
Heat Treating Terms
- Annealing
Annealing is the process of softening steel, usually done in preparation for working and grinding the steel. Annealing is done by heating up the steel past the critical temperature (the austenizing temperature) and then letting it cool slowly.
- Hardening
Hardenizing consists of two steps, austenizing and quenching. First, to austenize, the steel is heated to its critical temperature. To harden, the steel has to cool down more quickly than in the annealing step describe previously. So the steel is quenched -- allowed to cool -- in some medium such as oil, water, air, or molten salt, depending on the steel.
- Tempering
Once the blade has been hardened, tempering is done to reduce the hardness and relieve internal stresses in the steel.
Steels
- Stainless
The exact definition of when a steel becomes "stainless" is not rigidly defined, but most describe any steel with >13% chromium in it as "stainless". Of course, steels aren't completely stainless -- they will rust if given the chance -- but stainless steels resist rust much longer by virtue of their high chromium content.
Many stainless steels are used for cutlery. The low-carbon high-chromium steels, such as the 3xx series and 420 stainless are usually seen in applications such as dive knives, where rust resistance is much more important than edge holding. The next step up in edge holding is to go to steels with more carbon, such as 425M, 12C27, 440A, and AUS-6. As you go up in carbon, you are getting less rust resistance, but typically you're adding hardenability and thus edge holding. We can step up again to GIN-1, 440-B, 440-C, and AUS-8. AUS-10, ATS-34, ATS-55, and 154-CM have better edge-holding still. Some steels that aren't seen as often but show great promise are BG-42 (close to ATS-34 but with added vanadium) and CPM's 440V and 420V steels. All those steels have excellent edge holding, with 440V and 420V being just incredible.
- Non-Stainless (carbon and alloy steels)
There are a wide variety of non-stainless steels used in knifemaking. These steels do not focus their alloy mix on being rust-resistant, which means they are instead focussed on edge retention, superior toughness, or both. As a result, provided you're willing to put up with a little extra maintenance, you can see great performance results with these steels. Among the steels you'll see are the 10-series (1095 for knives, 1084, 1070, 1060, 1050 for swords), O-1, W-2, A-2, L-6, D-2, and 5160. You'll also see the great edge-holding 52100 steel, in knives made by those who forge their steel.
- Damascus
Damascus is made from two or more metals welded together. Most damascus has a striking beauty, obtained when the final product is acid etched. The two different metals in the damascus etch at a different rate, leaving a striking pattern. Many damascus steel knives are forged strictly with the objective of obtaining a beautiful pattern. However, there are many makers forging damascus with an eye towards performance. Such damascus might be made from O-1 and L-6, for example. Stainless damascus has also become available.
- Non-steels Used For Knives
A number of materials are used to replace steel in knife blades, with varying success. At the lowest end are the cheap CIA Letter Openers, with zytel-like blades. These knives aren't really a serious contender against steel, performance-wise.
Some of the tough high-tech handle materials, like G-10 and carbon fiber, are being used in knives today. They don't take an edge like steel, but are completely undetectable and non-magnetic, and some can make passable last-ditch weapons. Some makers are binding a very thin layer of steel to thicker layers of carbon fiber. The steel provides a working edge and the carbon fiber reinforces the steel for strength. The knife remains very lightweight due to the small amount of metal used, but the edge remains steel and so performs better than a synthetic edge.
Ceramic composites are being used by several manufacturers and makers. Their primary benefits are that they hold an edge much longer than any steel, and that they are completely non-corrosive. On the down side, they are much more brittle than steel. The worst of them can easily break by just a small drop to a hard table; however, the best of the ceramics is reasonably tough, tough enough for hard chopping and the like.
Cobalt-based alloys also show a lot of promise. They hold an edge for a very long time, and non-corrosive, and are much tougher than ceramics. These alloys -- such as Stellite 6K, Boye Dendridic Cobalt, and Talonite -- are much more expensive to work than steel, but tests are showing excellent results.
Titanium is also used as a blade material. Non-corrosive and much lighter than steel, it can take a reasonable edge and holds it okay. The cheaper titanium alloys in inexpensive dive knives are vastly overshadowed by the best titanium alloys.
