A Primer on Pocket Knives - Work in Progress!

EDC Gear for Flashlight Carriers
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Hey all, since I've got some time over the next month or so, I thought I'd start writing up a primer on knives (as it seems to be a pretty popular topic 'round these parts). This primer will be in multiple sections and I'll do my best to find useful diagrams and pictures to illustrate points. Alright? Let's get started.

Part 1: Types and Styles of Knives

Before we get started, just a little bit of vocabulary:

Tang: When you use the word "tang" with a knife, it generally means the unsharpened portion of the knife that extends beyond the sharpened blade area.

Fixed Blade Knives:

Fixed blade knives are just what the title would suggest. The knife is a single piece, generally a piece of steel with either a partial or full tang. Fixed blades are stronger than folding knives, but are generally heavier and larger. They're used when in the following cases:

1. Absolute strength is paramount (such as in a survival knife)

2. Portability or weight concerns are not an issue. (such as in a chef's knife)

3. Speed and simplicity of access is important for self-defense (such as in a soldier's or policeman's fighting knife)

There are two main styles of fixed blade knives.

Full-Tang Knives

When a fixed blade knife has a single piece of steel that extends from the tip of the blade all the way to end of the handle, it is considered to have a "full tang". Full tang fixed blade knives are the strongest type of knife, but also the heaviest and most expensive to produce. A classic example of a full tang knife is the Ka-Bar USMC Fighting knife, a soldier's knife designed for World War 2 and sold to this day.

Example of a full-tang knife, courtesy of cgrif42

Partial or Hidden Tang Knife

A fixed blade knife is considered to have a partial or "hidden" tang when the blade tang does not extend all the way to the end of the handle. This is generally a weight-saving measure, but also makes the knife less expensive to produce. Mora survival knives from Sweden tend to have partial tangs.

Xray of various Mora knives showing the partial tang. Courtesy of wordtrekker.blogspot.com

Folding Knives

Folding knives come in many different shapes and forms, but the common thread to all of them is this: Folding knives generally have a hinge or pivot system that allows the blade to somehow fold in to the handle. How this hinge is executed and how the knife is kept from collapsing when deployed is handled in any number of ways.

The major advantage that folding knives have over fixed blade knives is that of blade size: for a given weight and length, a folding knife can carry a much larger blade than a comparable fixed blade knife. The major detriment to folding knives over fixed blade knives is that they cannot be as strong as a fixed blade knife due to physical restraints.

Generally folding knives are used in the following situations:

1. Where weight or size are of a paramount concern (hiking, camping, general soldier duty knives)

2. Where absolute strength is not required (every day usage or utility knives)

3. Issues of legal restraints (fixed blade knives are often automatically considered offensive weapons)

There are many different types of folding knives, so I'm just going to go over the basic types here.

Slip Joint Knife

The most common, best selling and most popular type of folding knife is the slip joint knife. The slip joint knife uses a piece of spring steel on the back of the knife that rests on a flattened portion of the blade tang to provide some resistance to closure during use. Slip joint knives do not employ a locking mechanism of any type, and enough pressure on the top of the blade is enough to close it.

In countries that have legal issues surrounding locking blade knives, slip joint knives are often a legal alternative (the UK and Germany are classic examples).

The vast majority of Swiss Army Knives made by Victorinox/Wenger are of the slip joint style, and it is a classic style of working knife made the world over. Some famous slip joint knife makers include Sheffield Tools, Schrade Cutlery, Queen Cutley, Case XX, Victorinox/Wenger, Taylor's Eye Witness and many others.

An exploded view of a multi-blade slipjoint Case Knife, courtesy of Custom Tacticals.

Lock Blade Knife

As the name would imply, a lock blade knife employes a locking mechanism when opened to prevent closure of the knife during usage. This requires a secondary step by the user to close the blade, and exists to prevent accidents under heavy usage. It should be noted that there are no blade locks proven to be immune to failure under heavy usage. There are a very large number of different locking mechanisms currently available on the market today, and as such I'll be dedicating a full article on them alone. Some classic lock styles include the collar lock, back or spine lock, liner lock, frame lock and axis lock.

The classic example and probably best known locking knife is the Buck 110 Folding Hunter. This knife employs a back lock.

Buck 110 Folding Hunter showing the back lock. Courtesy of Waka Waka

There are three subsets of locking knives to be aware of:

1. Two Handed Opening (THO): As the title implies, this type of folding locking knife requires two hands to open. The Buck 110 pictured above is a THO knife.

2. One Handed Opening (OHO): As the title implies, this type of knife can be opened with one hand, utilizing a thumb disk, thumb stud, flipper tang or hole in the blade. Spyderco is generally credited with creating the first production OHO pocket knife.

3. Assisted Opening Knife: This knife employs a spring or torsion bar to provide an assist to the opening of the knife. This style of knife differs from a switchblade in that the opening mechanism is attached to the blade, rather than a button or switch on the handle. This is an important legal distinction in many place.

Friction Folders

A somewhat rarer type of folding knife, the friction folder uses neither a back spring or a locking mechanism to keep the blade open. Instead, the friction of the handle halves around the back of the blade keep the blade open. Friction folders often have an extended tang "spoon" that goes under the palm when the knife is open, providing extra security. Many traditional folding knives are a type of friction folder - these include the New Zealand Peasant Svord, the French Douk-Douk and the Japanese Higonokami.

A peasant Svord knife, showing the extended tang "spoon". Picture courtesy of Dirty Bob of the EDCForums.com

A traditional Higonokami, showing a smaller tang "spoon". Picture courtesy of Alexander Blecker.

The Balisong or Butterfly Knife

Featured in many films of the 80s and 90s as a gang knife, the Balisong (or butterfly knife) of the Phillipines is in fact one of the first true one handed opening pocket knives ever created. The balisong is unique among folding knives in that instead of a blade being attached to the handle via a single pivot, the handle is split in half and swings freely on two pivots. The handles can be folded forward to protect the blade, or folded back to create the knife handle. This particular system is 100% stable against folding during use, but it should be noted that this style of folding knife, like all others, can fail on heavy usage. The failure point in this case is the pivot between handle and knife. Generally used as a self-defense/weapon knife in North America, the balisong is an every day usage knife in it's native Phillipines.

The traditional Balisong, picture courtesy of www.varietyartsclubdirectory.com

Switchblades and Automatic Knives

The last major category of folding knife is that of the switchblade or automatic knife. Generally when one thinks of a switchblade, the first image is that of the classic Italian stilleto switchblade - very thin, with a button on the handle that shoots the blade out of the front. In North America, this particular knife is the iconic 50s "greaser" knife, replaced in movies and TV shows with a switchblade comb.

However, there is much more to know about this particular style of knife. Legally, the category of switchblades and automatic knives includes any knife that uses a spring or torsion bar to provide an opening assistance mechanism, and said mechanism is actuated by a switch or button not attached to the knife blade. This switch or button is generally attached to the knife handle instead. This is different compared to the assisted locking knife, which uses a spring or torsion bar for opening assistance, but the opening mechanism is attached to the knife blade, either through an extended flipper tang or with the thumbstud. This distinction is very important as it forms the legal difference between assisted opening knives (which are generally legal in most parts of North America and other Western nations), and switchblades or automatic knives (which are generally not legal for the public).

Button-actuation automatic knives find most widespread use in either military or law enforcement hands in North America. Considered a close-quarters weapon of last resort, the automatic knife is considered an excellent "under duress" knife as the button actuation is extremely simple, even under stress. The largest maker of military-grade automatic knives is Microtech knives.

For comparison's sake, we have on the top the Kershaw OSO sweet, and on the bottom, the Microtech Socom Elite Military Automatic knife. When closed, the extended "flipper" tang on the Kershaw OSO sweet is plainy visible sticking up through the top of the handle. This is the feature that puts the Kershaw in to the assisted knife category, an importang legal distinction. On the right, we can clearly see the actuation button on the handle of the Microtech knife, which categorizes it as an automatic knife. Pictures courtesy of kershaw-knives.net and CustomTacticals.com.

A picture of a classic Italian stilleto-style switchblade. Note the button on the handle used for actuation. Picture courtesy of nicnac.net

Here ends primer section number 1 on pocket knives. Next week: Locks!

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Nice! Sticky'd. Thanks for your hard work jekostas.

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Nice work so far, jekostas.

I own a Buck 110 like you show in the photo above. Nice, hefty knife, solid build.

Can't wait till tomorrow, my favorite knives are assisted-opening ones, especially ones with partial serrated blades.

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Awesome work jekostas!

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Excellent! I like learning the right terminology.

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Note: Since Photobucket seems to be having issues right now, I'll be updating this post with pictures when I can.

Part 2: Locking Mechanisms

Alright, part 2 of my pocket knife primer, locking mechanisms. There are as many locking mechanisms and variations on them as there are days in a year, so I'm going to focus on only the most common styles, those being the collar lock, back lock, liner lock, frame lock and axis/piston lock. I'll be going over some of the positives and negatives of each locking style.

Again, before we get too far in let's get a little bit of vocabulary out of the way.

Positive Pressure: When cutting with a knife, any pressure placed up against the edge of the blade is called "positive pressure". This is the most common form of stress placed on a knife, and any cutting task involves this stress. Chopping with a kitchen knife would be considered positive pressure.

Negative Pressure: When stress occurs against the top spine of the blade opposite to the cutting area, this is called "negative pressure". Negative pressure most often occurs when digging, picking or prying with the tip of a knife blade.

Lateral Pressure: When stress occurs either laterally or rotationally to the blade, it is considered "lateral pressure". This most often happens with stabbing, twisting or prying actions with the flat of the blade.

Stop/Anvil Pin: In may types of locking knives, there is a small pin set in to the handle that performs two functions. First of all, it proscribes the maximum opening angle of the blade around the pivot, providing a "stop" on the blade tang. Secondly, it transfers stress from positive pressure in to the knife handle and away from the pivot holding the blade.

The stop/anvil pin on a Spyderco Paramilitary, courtesy of Frapiscide.

What do Blade Locks Do?

While the idea of keeping the blade locked in the open position in use is the more easily understood function of a blade lock, all knife blade locks actually perform a second, equally important function.

Blade locks also provide blade retention: that is, when the knife is folded for storage or carry, the blade lock provides some locking force to keep the knife in the handle so it won't open on it's own. If you stop and think that most pocket knife are carried in the front pants pocket, you can understand how important this function is!

Types of Blade Locks

Collar Lock

A type of lock first produced and used almost exclusively by Opinel knives of France, the Collar lock is a simple rotating metal collar with a slot in it. When the slot in the collar lines up with the pivot of the knife blade, the knife can be opened or closed. When the collar is twisted to either side, the blade is securely locked in to place against the stop pin.

Pros: Extremely stable, inexpensive to manufacture and machine.

Cons: Slow, not possible to open or close with one hand. Can be easily damaged from abuse to the collar or the handle material.

An Opinel #8 Knife showing the the Collar Lock

Liner Lock

The most common and widely produce blade lock in existence, the liner lock uses a piece of spring steel that pops in to place behind the blade tang when the knife is completely opened. This wedges the blade between a stop pin set in to the handle of the knife, and the back of the blade tang. To close the knife the liner needs to be moved off to one side, at which time the blade can be folded back in to the handle. As the name implies, the piece of spring steel is generally a liner, with a secondary material placed outside of the liner to form the handle of the knife. The blade tang is generally machined on a slight angle, allowing for metal on metal wear and still providing a secure locking force without blade movement.

Often, there is a small ball bearing set in to the lock spring - when the blade is closed in to the handle, it slots in to a small groove machined in to the blade, providing enough force to keep the blade from opening on its own.

Liner locks are considered light-medium duty locks. While extraordinarily stable against positive pressure stress due to have a built in stop pin, they are susceptible to failure from negative pressure.

Custom knifemaker Michael Walker is credited with creating the Liner Lock in 1980

Pros: Simple to machine and manufacture. Self-wearing lock. Reliable under positive pressure. Can be opened and closed extremely quickly.

Cons: Can be fouled by dirt, mud or other contaminants. Can be defeated by negative blade pressure.

Frame Lock

The Frame Lock is a modification of the liner lock. Instead of the locking spring being formed by a steel liner inside the handle of the knife, the knife handle itself is machined in to the lock, requiring some sort of metal handle (generally 400 series stainless steel or titanium). Otherwise the mechanics of the Frame Lock are generally similar to the Liner Lock, though some manufacturers add a lock stop to prevent the locking bar from being bent to far outward when disengaging the lock.

Frame locks are generally considered heavier duty locks than liner locks. The reason for this is that when a frame lock his held in the hand, the grip of the hand on the handle will actually provide extra security against the lockbar disengaging under force. They are as stable against positive pressure stress as liner locks are doing to having a stop pin. The major negative point is that since the handle must now be made of metal, it increases the overall weight of the knife.

Custom knifemaker Chris Reeve is credited with creating the Frame Lock, also called the Reeve Integral Lock.

Pros: Simple to machine and manufacture. Self-wearing lock. Reliable under positive and negative pressure. Can be opened and closed extremely quickly.

Cons: Requirement for a metal handle can significantly increase the weight and cost of a knife. Lock can be stressed if opened too far.

Back Lock

One of the first production locks ever made, the back lock remains one of the most popular locking mechanisms on the market today. The back lock (or spine lock as it's sometimes known) is made of three parts. The blade has a notch cut out near the tang, just above the pivot. The locking spine has a key portion cut out that slots in to the notch on the spine, providing a holding force for the blade, and there's a small spring (either leaf or coil, but leaf is more common) that provides the pressure necessary to keep all the parts of the lock in place when opened.

When the blade is closed, the downward pressure exerted by the fore part of the back lock keeps the blade held in the handle.

Back locks are considered one of the strongest types of lock as they are highly resistant to negative pressure. This is due to the key-lock slot design of the lock - for the blade to fold under negative pressure the entire lock needs to be disengaged. Back locks are popular on heavy duty hunting knives and heavy use military knives where stabbing (either in a defensive action or to penetrate skin for skinning) is a normal need. Conversely, back locks do not use a stop in their design and as such they can be susceptible to failure from continual positive pressure usage. This is especially true if the lock up is not well machined, as the movement in the blade puts stress on the spring system.

Buck Knives is credited with producing the first back lock knife with the Buck 110 Folding Hunter

Pros: Very strong lock, highly resistant to negative pressure. Resistant to dirt or fouling. Simple lock to manufacture. Fully ambidextrous.

Cons: Spring can be stressed by positive pressure, causing lock failure. Not easy easy to open or close as a liner or frame lock.

Axis Lock/Piston Lock

The term "Axis" was originally coined by Benchmade Knives in the late 1990s, and they currently hold a trademark on the term as it deals with knife locking mechanisms. However, the Axis lock is but one lock of an entire family of locks called piston locks that function in a very similar way. The Axis lock and other locks of this type function all in the same way: When the knife is opened, the blade butts up against a stop pin set in the handle, and an axis, bearing, sliding piston or locking button attached to a spring in the handle rests on the top of the extended blade tang, holding the blade up against the stop pin.

Axis type locks use the same forward spring pressure from the locking bar to keep the blade closed.

Axis and piston type locks have a significant number of advantages to them. They are easy to make fully ambidextrous. They can be opened and closed easily. The lock mechanism is generally self cleaning and thus resistant to contamination from dirt or debris. The lock mechanism is highly resistant to both positive and negative blade pressure in cutting, creating a very safe lock up. The major con to Axis or Piston type locks is that the machining required to make an effective lock is very precise - this generally increases the overall cost of a knife. Axis locks also rely on spring pressure to keep the blade open more than other locks, and springs can wear out over time.

While Benchmade has the most famous interation of this lock, there are many, many types of Axis or Piston locks on the market. They include:

Sog Arc-Lock

Sog Piston Lock

Spyderco Ball Bearing Lock

Gerber SAF-T-LOK

Gerber FAST Lock

Gerber Slide Lock

Cold Steel Ultra Lock

Victorinox Slide Lock (used exclusively on pliers-based multitools)

Pros: Self-cleaning and resistant to contamination. Ambidextrous. Resistant to positive and negative blade pressure. Easily opened and closed with one hand.

Cons: Expensive and time consuming to machine. Relies on spring tension for blade lockup.

A SanRenMu 763, showing the Axis bar resting on top the extended blade tang, and the locking bar.

That's about it for this section. There are many other types of locks on the market, including button locks, various types of thumb stud locks, and many variations on the above, but they command very little of the market.

The question you may ask is "What's the best lock?" The straight answer to this question is there isn't one. You need to ascertain your needs, your price point and what you're willing to pay for. While a liner lock is generally considered the weakest of the locking mechanisms, the honest truth is that in regular usage the pivot on a knife (the point where the blade and handle are joined) is much more likely to fail than ANY locking mechanism. My personal preference is the liner lock, due to the speed with which it can be opened and closed.

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Part 3: Knife Steels

Alright folks, time for part 3, knife steels and their important qualities. Please note that I'm not going to be doing an indepth comparison of all the literally hundreds of different knife steels on the market or their chemical components. If you're interested in that sort of information, I would highly suggest the following site: http://zknives.com/knives/steels/index.shtml

ZKnives has been around for a very long time, and is updated on a pretty regular basis.

I should warn you now, there's going to be lots of words and very little in the way of pictures in this post, so feel free to skim to the bits that interest you the most.

First, some vocabulary:

Heat Treatment: The heat treatment is the process by which a knife is heated and cooled to give it it's basic properties (those listed below). This is generally a two step process from raw steel, which is hardening (brining a knife to an acceptable hardness level) and tempering (removing brittleness and setting the grain properties).

Edge Retention: How long a blade is able to keep a safe cutting edge.

CPM: Composite Powder Metallurgy. A process where by a steel is ground in to a microscopic powder and then reformed under intense heat and pressure. Extremely expensive and relatively rare, but the refined grain structure provided by this process significantly increases a steel's edge retention and sharpenability.

The Important Qualities of Steel

Hardness: Probably the first aspect talked about with any knife steel, hardness is exactly what it sounds like - how hard a steel is. Hardness is measured in Rockwell Units of Hardness (HRC), and knives for sustained cutting usage generally fall in the 48-65 HRC range. It should be noted that Rockwell Hardness is a logarithmic scale, and as such the the difference in even 2-3 points in the hardness scale is an enormous amount. Most knifemakers say that a 2 point difference in HRC is noticeable in cutting performance. The harder a steel is, the longer it will hold an edge and to some degree high hardness also makes a knife difficult to sharpen (as sharpening involves removing steel). Without some clever alloying, high hardness steels can also become brittle - more likely to break or chip with abuse. Hardness is a primary factor in determining how long a knife can hold an edge.

Hardness is important for every day carry knives, specialized skinning knives, whittling knives and knives used for detail work. This type of knife is generally not used for heavy work, and values absolute edge retention over sharpenability.

The amount of carbon in a blade generally determines its absolute peak hardness (though this is not a hard and fast rule).

Toughness: The flip side to hardness is toughness - how likely a knife is to break under pressure. Toughness is also called tensile strength or ductability. Steels that are tougher tend to be softer (ie. not as much hardness), but are more likely to roll or bend rather than chip or break. A rolled edge or bent knife is repairable without lasting consequences - chipping or breakage is not. A good comparison for hardness and toughness is the difference between glass and lexan. Glass is very hard, so much so that it can actually be used for structural support. However, glass is prone to breakage from sharp blows and abuse. Lexan, while not nearly as structurually hard, is much tougher, and much more resistant to abuse without breakage.

Toughess is important for work site knives, camping knives, heavy usage knives and specialized self-defense knives. These knives are generally used for hard work, and thus value easy sharpenability above absolute edge retention. There is often a trade-off between hardness and toughness in a knife, but to some degree this trade-off is being minimized through alloying and advances in metallurgy.

Corrosion Resistance: Corrosion resistance is the ability for a steel to resist corrosion, either from constant exposure to chemical contaminants, salt water or sweat. Corrosion resistance is generally controlled by the amount of chromium in the steel's composition. The higher the chromium, the higher the corrosion resistance. This balance must be carefully controlled as chromium has a secondary effect of weakening steel - bringing down the hardness without increasing the toughness. So-called "stainless" steels have a minimum chromium content of 12%.

Corrosion resistance has a secondary effect on edge retention. Since the knife edge is the thinnest part of the blade and the most in contact with possible contaminants, it's the part most likely to corrode. High corrosion resistance can help minimize this problem.

High corrosion resistance is important for knives meant for working around water and chemical contaminants. Up until about 5 years ago, knives meant for water work tended to be made of very soft alloys, as they could not have a lot of carbon in them as carbon is the major catalyst for corrosion.

Wear Resistance: Wear resistance is a secondary characteristic of steel, and generally denotes a steel's ability to resist scratching and damage from use. Wear resistance has a secondary effect on edge retention, as high-wear steels will have their edges worn away faster.

Wear resistance is a secondary characteristic among steels and isn't generally the major selling point for a knife.

Sharpenability: The one constant among all materials used for cutting is that they will eventually dull, and need to be resharpened. To a major extent, how easy a knife is to sharpen is the trade-off between hardness and toughness chosen in alloying the steel. Knives with harder steels are generally tougher to resharpen but hold an edge longer, knives with tougher steels are easier to sharpen but don't hold an edge as long.

However, this is not a hard and fast rule - there are some elements (notably molybdenum and vanadium) that will will refine the grain structure of steel alloys, making sharpening much easier even for very hard steels.

Types of Steels

Stainless Steels

The most prominent type of steel on the market today, so called "stainless steels" have a minimum chromium content of 12%. Free chromium in alloy reacts with oxygen and creates chromium oxide molecules on the surface of the steel, preventing oxidization of the iron in the alloy. Chromium also has the secondary effect of weakening steel alloys, and as such stainless steels are often considered second to carbon or tool steels in terms of absolute strength and hardness, though this is starting to change over time. Common stainless steels include:

420HC: A low-carbon stainless steel, generally valued for it's toughness rather than it's edge retention. Commonly used by Buck Knives and Leatherman Multitools

440A/440B/440C: Stainless cutlery steels, not often used any more. Roughly correspond to .4%/.6%/.8% in carbon content, with 440C making a very reliable knife blade. When you see a steel labelled as "440 stainless", it will generally be some form of 440A steel. Gerber's "mystery steel" is 440A stainless steel

AUS-4/AUS-6/AUS-8/AUS-10: Japanese-developed stainless steels made to compete with the 440 series. The number in the steel denotes the amount of carbon present in 1/10th of a percentages. Was considered a high-end steel a decade ago, but AUS-8 is the only variation that continues to see regular usage, mostly from Cold Steel knives.

3Cr13, 5Cr13Mo, 8Cr13MoV: Chinese-developed stainless steels, developed to be comparable to the Japanese AUS series. Becoming very popular. 8Cr13MoV is a solid, midrange steel that combines good edge retention, high toughness, and easy sharpenability with moderate corrosion resistance. Used by many knifemakers, including Spyderco, Kershaw, CRKT, SanRenMu, Bee, etc.

VG-10: A high-end Japanese developed cutlery steel, VG-10 is one of the current darlings of the knife world. VG-10 combines moderate toughness with very high hardness, very high edge retention and very high corrosion resistance. Due to an export restriction, all knives made using VG-10 are made and finished in Japan.

154CM: An American-made cutlery steel, 154CM was developed as a tool steel, but modified for usage in knives. It is very similar in day to day usage to VG-10, with higher toughness but is considered more difficult to sharpen. 154CM is widely used by Benchmade and Leatherman. Available in both standard alloyed and CPM versions.

S30V: One of the current darlings of the knife world, S30V combines extremely high toughness with very high wear resistance to provide excellent edge retention. Mostly available in CPM versions.

DIN 1.4116: An incredibly common, low-cost stainless steel developed in Germany, DIN 1.4116 is the steel used in Swiss Army Knives produced by Victorinox and Wenger. It combines high toughness, moderate hardness, easy sharpening and very high corrosion resistance. This steel is starting to gain favour with other manufacturers as a low-cost alternative to Carbon or Tool steels in outdoor usage knives (notably Cold Steel).

Carbon or Tool Steels

The term "carbon" steel used to mean a steel with a minimum alloying of .6% carbon by volume, but with the increase in marketing, this term really doesn't mean much any more. It has mostly been replaced by the term "tool" steel. Carbon or tool steels have less than 12% chromium. As such they have relatively poor by corrosion resistance but can have better hardness and toughness than stainless steels. Carbon or tool steels generally have some sort of factory coating to prevent corrosion. Common carbon or tool steels include:

1075/1085/1095: A very basic steel alloy, but easily sharpenable and very tough. The last two numbers represent the amount of carbon present in the alloy in 1/10ths of a percentage. Often used in high-end survival knives. Corrosion can be a problem and 10xx steels tend to have some sort of paint or electrolytic coating for protection.

D2: A high-end steel developed for use in ball-bearings for high-speed machining. Very hard (in the 61-62 range) and surprisingly tough, D2 has a reputation for being difficult to sharpen. Used in some high-end survival knives and folding pocket knives

BG-42: Originally a high-tensile spring steel, BG-42 was developed as a knife steel by changing the heat treatment. BG-42 has very high hardness and toughness combined with reasonable corrosion resistance, but is known as very difficult to sharpen. Generally used in survival knives.

Water Knives

Water knives tend to have very low amounts of carbon to prevent oxidization, and as such are generally very soft steels. Designed mostly to work on fishing boats, as dive knives or as kayaking/canoeing knives, water knives are generally highly specialized and not found much in the generally public. However, in the last 5 years or so with the development of H1 steel by Spyderco, water knives are becoming much more popular as H1 has comparable edge retention to good stainless steels. Some common water knife steels include:

Dendritic Cobalt/Tallonite/Stellite: These metals (not technically steels) used cobalt as an alloying element instead of carbon. Due to the lack of carbon, they tended to be extremely soft (max of 51HRC), and as such never found much use in the general public. Some custom made Boye water knives still use these materials, but as they aren't produced any more it is extremely rare.

Titanium: Titanium and a few of it's alloys can be hardened in to the 51-53HRC range, which puts them at the very bottom of the hardness threshold for usable knives. However, titanium does not rust. Titanium is popular for backup diving knives and river rafting knives.

H1: A relatively new material (not technically a steel, technically a "metallic ceramic"), H1 steel was developed by Spyderco to be the ultimate water knife. H1 uses Nitrogen instead of Carbon as it's hardening element, and as such is impervious to corrosion. It is otherwise chemically similar to other stainless steels. H1 also has a couple of notable distinctions: it's one of the very few work-hardening steels available in knives, and as such gets harder the more you use it. Secondly, H1 has extraordinary toughness qualities, and as such even under incredible stress will not break. The downside to H1 is that it has very low wear resistance and thus only moderate edge-holding capabilities. It is still far superior to Titanium or Cobalt-based knives, however. H1 is only used by Spyderco knives.

Damascus Steel

Damascus steel is generally a very hard, high-carbon steel core covered by many layers of softer, low-carbon steels. Damasacus was originally developed out of necessity - the best steels for cutting were very brittle and had poor corrosion resistance, limiting their overall use. Covering the steels in tougher, corrosion resistant layers corrected both of these problems. However, Damascus steels are expensive and time consuming to produce, and with the advent of stainless steel the need for them has decreased. Damascus steels are generally an asthetic, rather than a functional choice.

Other Materials

There are other materials used to make knife blades, including various zirconium ceramics and obsidian. While being extremely hard and capable of taking an extraordinary edge (obsidian is often used for fine surgical blades), these materials are also extremely brittle and prone to breakage with very little use. They are generally considered conversational pieces and nothing more.

Alright, that's it for steels - next section, blades and blade shapes!

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Part 4: Handle Materials

Alright, we're up to part 4 - handles and handle materials. Besides providing decorative touches, handle materials can also contribute significantly to the stiffness and overall build of a knife. Some materials like carbon fiber and bone are only used as decorative handles on top of steel liners for strength reasons, while other materials, such as G10, FRN and Micarta can be used with or without steel reinforcement.

Again, before we start just some vocabulary:

Liners: When we call a handle "lined" or "unlined" it means whether or not there are reinforcing steel liners have been placed in the knife handle. In some case they provide structure to prevent the force of the lock from torquing the knife, in other cases they provide ductile strength to prevent handle materials from cracking under stress. Nested liners are hidden, generally in cutouts in the handle. Unnested liners are generally not hidden. All slipjoint knives employe steel liners to prevent the backsprings from moving out of place.

Nylon and Nylon Composite Handles

Nylon/Thermoplastic: A basic, heat-formed hardened plastic, pure nylon or thermoplastic handles are rarely if ever used. They tend to lack any kind of toughness or wear resistance, and as such are easily damaged through abuse. Only found on the very cheapest of knives, or, paradoxically, on some high-end survival knives where handle strength is of limited concern.

Fibreglass Reinforced Nylon (AKA FRN, Glass-Reinforced Nylon, Zytel, Grivory, Valox): Probably the most popular handle material used for making pocket knives, FRN uses fibreglass reinforcement to add strength and wear resistance to nylon. This type of handles material has some very significant advantages: It's inexpensive to make and machine, it's highly resistant to wear, shock, acid, damage and abrasion, as well as being extremely resistant to temperature changes.

There are a couple of downsides to FRN, however. The major issue with most forms of FRN (though specific formulations may change this) is that they lack hardness - they're tough, but extremely flexible. As such, FRN often needs some sort of stiffening element such as aluminium or steel liners to support the stresses of the lock. FRN is also diffcult to texture for grip and in many people's minds, feels cheap. FRN remains one of the most popular handle materials for knives.

G10: G10 is another extremely popular handle material use to make knife handles. G10 is actually an epoxy resin laminate of fibreglass reinforced nylon, and as such has many of the major advantages, including resistance to wear, temperature, abrasion and acid. G10, being a layered material, is also much easier to texture using CNC machining techniques. G10 also has signficantly more structural hardness than FRN. In essence, G10 is FRN that's been cut in to extremly thin strips, and then laminated together using an epoxy. G10 IS nominally FRN, but with an extra manufacturing process.

There are some negatives to G10, however. G10 can be extremely brittle and as such generally requires some sort of strengthening element to prevent cracking with use (not always the case - some Cold Steel knives have G10-only handles). Since G10 doesn't flex, it can also create "hot spots" in grip if not designed properly - spots in the grip that become painful after prolonged usage.

Metal Handles

Stainless Steel: Generally made from 410-series or 300 series stainless steel, stainless steel handles are a popular choice for knives that are made to be extremely thin, use frame locks, or for gentleman's knives. Properly hardened steel has many useful properties, including high wear resistance, structural strength, toughness and looks. Stainless steel also rarely has the "hot spot" problem inherent with G10.

There are many negatives with stainless steel handles, however. Weight is a prime concern. Grip is also a major issue, as texturing stainless steel to provide grip often leads to corrosion issues. This problem is generally fixed with some sort of rubber handle insert. Stainless steel are also sensitive to temperature changes and can warp.

Titanium: Used on higher-end production knives and custom folders, titanium is generally used in place of stainless steel in making handles. It has many of the benefits of stainless steel, with the major improved benefit is that titanium (and many of it's alloys) are impervious to corrosion.

Titanium also has many of the major negative issues of stainless steel, including decreased grip, sensitivity to temperature chances and warping. Titanium, due to it's flexibility, also generally needs to be much thicker than a comparable stainless steel handle to provide the same strength, which generally does away with any desired weight gains. Last but certianly not least, titanium does not have the wear resistance of stainless steel, so lock components made of titanium will wear and fail MUCH faster than those made of steel.

Aluminum: Aluminum has again many of the major benefits of stainless steel, but is considerably lighter.

The major negative point to aluminum is that it does not have the structural strength to make a lock out of the material. Generally knives that use aluminum handles will use nested steel liners to create the lock components. Aluminum also scratches extremely easily.

Other Composite Handles

Micarta: A trademarked name, micarta actually refers to an exposy resin composite made of fibrous, natural materials in sheet form. As such, it's possible to have paper micarta, denim micarta, canvas micarta or any number of other choices, including rarer forms such as silk micarta (normally made of parachute silk) or carbon fiber micarta. Micarta is generally used for looks in a handle material and generally includes some sort of strengthening liner. It otherwise has many of the benefits of FRN, including resistance to acid, abrasion and temperature changes.

There are many negative points to micarta, however. Because of the difference in materials used, micarta is difficult to form and machine. The material is extremely finicky in machining and generally requires some sort of final polishing stage done by hand (which significantly increases cost). Micarta tends to be brittle and will crack if great care is not taken in production (such as drilling holes for screws), and is susceptible to breakage from normal wear and tear.

Pakkawood (aka Dymondwood): Pakkawood, not a real wood, is in fact a compressed expoxy mixed with sawdust to create a machinable handle. Pakkawood can be "brushed" during production to create the appearance of wood grain, and takes dyes extremely easily. Generally pakkawood is machined and then finished with some sort of lacquer after dying. Pakkawood can also be laminated to create a multicolor effect. Pakkawood is an extremely strong, extremely stable material the can be used alone to create knife handles without strengthening liners. Pakkawood is so stable in usage that it's an acceptable handle material the world over for creating chef's knives for working in restaurants.

The major negative point to pakkawood is that like real wood, it can be damaged with enough force and as such is rarely used in hard working knives. Some people also find it really cheesy looking. Dymondwood, a trademarked form of pakkawood, adds thermoplastic elements to the sawdust to increase the tensile strength of the material.

Carbon Fiber: Carbon fiber is generally used for looks alone, as it lacks the requisite structural strength to form a handle material on it's own. It is also extremely difficult to texture for grip and can be prohibitively expensive. Carbon Fiber dust is also poisonous, making the material difficult to work with.

Natural Materials

Wood: Wood's been used a knife handle for many, many hundreds of years, and that practice continues today. Mostly wood is used for looks, or wear significant handle strenght is not a huge concern (mostly used on fixed blade knives and not folders). When wood is used on folding knives it's always attached to some sort of metal liner. Wood is extremely tough, easily found and easily shapable, and finished properly it can be very beautiful.

Wood can also crack or rot, or dry out if not cared for properly. Just about all wood-handled knives on the market are pre-finished to help prevent these types of problems.

There are two types of wood handles on the market, stabilized and unstabilized. Stabilized wooden handles are generally soaked in water to remove the oils, and then soaked or injected with some sort of stabilizing resin for long-term wear resistance. This is extremely popular for knives used in bushcrafting or survival work. Unstabilized wood handles use kiln-dried wood covered in a lacquer, and is common on custom made knives.

Bone: Another material that's been used for many years to make knife handles, bone is generally used to makes scales (decorative or grip elements) rather than the entire handle as bone tends to dry up and lose tensile strength over time. Jigged or burnt bone handles are common on slipjoint knives and custom made knives.

Antler: Generally made from the antlers of the Indian Sambar, antler handles are another classic knife scale material. Like bone they tend to lose tensile strength as they age and as such are used only for decorative elements. Antler handles are also made from reindeer, white-tailed deer and other more common species of deer. In Africa it's common to make knife handles from antelopes such as Kudu or Rhebok.

And here ends part 4!

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Reserved.

10

Nice work!

11

Great illustrations and your writing style uses a nice relaxed tone.

I had a set of those Italian switch blades confiscated at the border when I emigrated to the USA at the tender age of 14! I bought them via mail order and didn't know they were verboten. When we crossed the border with our luggage someone asked me if I had anything other than clothing in my luggage. I innocently volunteered that I had some knives. They were very nice about it, but that was the last I saw of my knives.

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Hey all, just to let you know I will be getting back to this in a few weeks - life's been kinda crazy the last little while.

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No problem, take your time. This is nothing, that can be "rushed" out.

14

Thanks for the explaination of the different types of Knives

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This is a thread I will visit often, great job jekostas!

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Alright, part 2: locking mechanisms posted.

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It's great for me, to get so much information about knives. Thank you.

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Jekostas, please see photo and my most recent post in this thread

What do you make of that double-lock mechanism? I've never seen anything like it before.

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There are a couple different versions of double-locking mechanisms. The CRKT has a couple called LAWKS (Lake and Walker Knife Safety) and LBS (Lock Back Safety), Gerber has one called the Rotolock, and Lionsteel has one called the Rotoblock. They're supposed to provide an extra bit of security against lock failure, especially with liner locks. The problem is that any force great enough to cause a liner lock to fail will often break those secondary locks as well, or break the knife in such as way as to make the secondary lock useless (such as the pivot failing rather than the liner disengaging). Mostly a marketing thing.

Put it this way - if you expect to put a great enough to force on a liner lock where you think you'll need a secondary safety, it's much better just get a knife with a stronger lock, like a frame lock or back lock.

Edit: Just remembered, SanRenMu actually has a secondary lock on a couple of their knives as well.

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Good information, thanks. It's just not a one-handed closer.