Knife information you might want to know-very long read

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CPM T440V - CPM T420V

Two steels that hold an edge superbly (better than ATS-34), but it's difficult to get the edge there in the first place. These steels are both high in vanadium. Spyderco offers at least one model in CPM T440V. Custom maker Sean McWilliams is a big fan of 440V, which he forges. Depending on heat treatment, expect to have to work a bit harder to sharpen these steels -- also, don't expect ATS-34 type toughness. 420V is CPM's follow-on to 440V, and with less chromium and almost double the vanadium, is more wear-resistant and may be tougher than 440V.

400 Series Stainless

Before Cold Steel switched to AUS-8, many of their stainless products were marketed as being of "400 Series Stainless". Other knife companies are beginning to use the same term. What exactly *is* 400 Series Stainless? I always imagined it was 440-A, but there's nothing to keep a company from using any 4xx steel, like 420 or 425M, and calling it 400 Series Stainless.

NON-STEELS USED BY KNIFEMAKERS

Cobalt - Stellite 6K
A flexible material with very good wear resistance, it is practically corrosion resistant. Stellite 6K, sometimes seen in knives, is a cobalt alloy. David Boye uses cobalt for his dive knives.

Titanium

Newer titanium alloys can be hardened near 50 Rc, and at that hardness seem to take something approaching a useful edge. It is extremely rust-resistant, and is non-magnetic. Popular as expensive dive knives these days, because the SEALs use it as their knife when working around magnetic-detonated mines. Mission knives uses titanium. Tygrys makes a knife with a steel edge sandwiched by titanium.

Ceramics

Numerous knives have been offered with ceramic blades. Usually, those blades are very very brittle, and cannot be sharpened by the user; however, they hold an edge well. Boker and Kyocera make knives from this type of ceramic. Kevin McClung recently came out with a ceramic composite knife blade that much tougher than the previous ceramics, tough enough to actually be useful as a knife blade for most jobs. It is also user-sharpenable, and holds an edge incredibly well.

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BLADE GRINDS

The Hollow Grind

The hollow grind is done by taking two concave scoops out of the side of the blade. Many production companies use this grind, because it's easier to design machines to do it. But many custom makers grind this way as well. Its great advantage is that the edge is extraordinarily thin, and thin edges slice better. The disadvantage is that the thinner the edge, the weaker it is. Hollow ground edges can chip or roll over in harder use. And the hollow ground edge can't penetrate too far for food-type chopping, because the edge gets non-linearly thicker as it nears the spine.

For designs where slicing is important, but the slice doesn't need to go too deep, this grind is an excellent choice. Many hunting knives are hollow ground, because field dressing is often best done with a knife that slices exceptionally well through soft tissues. Unfortunately, if you hit a bone, you can chip the edge, so the flat grind (see below) is also used often.
Another advantage of the hollow ground knife, at least at the beginning, is ease of sharpening. Most hollow grinds thicken slightly towards the edge. That means that as you sharpen (at least at first), the blade gets thinner and easier to sharpen. After this, however, the blade begins thickening non-linearly and sharpening will become more difficult. The ultimate push cutter, the straight razor, is usually hollow ground.

The Chisel Grind

The chisel grind is a knife which is not ground at all on one side. So it is completely flat on one side, and has a bevel on the other. It is simple to produce (the maker need only grind one side), and simple to sharpen (it is sharpened on one side only, then the burr is stropped off the other side). It is also typically very sharp, due to the single bevel design. Whereas a blade ground on both sides might be sharpened at 20 degrees per side, for a total of 40-degrees edge angle, a chisel ground blade is often ground at around 30 degrees, making for a thin (and thus sharp) edge. Accurate slices are very difficult with the chisel grind, due to the fact that the non-symmetrical design forces the knife to curve in the medium being cut.

The Sabre Grind

The sabre grind is a strong edge format. The bevel starts around the middle of the blade, and proceeds flatly towards the edge. This leaves a strong edge for chopping and other hard use. But it also means the edge will be fairly thick, so this design will not necessarily slice all that well. The sabre grind is found on many military classic designs such as the Randall #1 and the kabar.

The Flat Grind

The flat grind endeavors to provide an edge that is both thin and strong, and leaves a strong thick spine. The grind is completely flat, going from the spine to the edge. This grind is harder to make, because a lot of steel needs to be ground away. However, the edge ends up being fairly thin and so cutting very well. Because the bevels are flat, there is plenty of metal backing the edge, so it's much stronger than a hollow grind. It is not as strong as a sabre grind, but will outcut that grind.

The edge on this design also penetrates better for slicing and chopping. The hollow grind expands non-linearly as you go up the blade, the sabre grind expands linearly but very quickly. The flat grind expands linearly and slowly. Kitchen knives are usually flat ground, because when chopping/slicing food you need to push the blade all the way through the food. This grind is an outstanding compromise between strength and cutting ability, sacrificing little for either.

The Convex Grind

Also called the Moran grind, after Bill Moran. This grind is as you would expect, the grind arcs down in a convex curve down to the edge. This means the point can be very sharp, because there's no secondary bevels to create the edge itself, just two intersecting arcs. There is also a fair amount of steel behind the edge, because the convex arcs cause the edge to widen non-linearly. This is a strong-edge format, which won't penetrate like a flat grind but will be stronger. Knifemakers form this grind on a flat-belt grinder. A disadvantage of this grind is if you don't have a flat-belt grinder yourself, it is difficult to touch up the edge.

The Dual-Ground Reinforced Tanto

The Americanized tanto as executed by Cold Steel shows multiple grind types. Along the long flat, the knife is hollow ground, for a thin edge and incredible sharpness. However, along the front up to the point, the grind switches to a flat grind. This provides incredible tip strength. The result is a knife with a very keen bottom edge, but a strong profile towards the front where it pierces. Of course, the reinforced front edge is strong but doesn't pierce easily.

CUSTOM
VI. Putting It All Together

Okay, now we know the characteristics, grinds, and blade shapes, and what they are all good for. If you understand this, you can begin to see how to mix and match features to fine-tune a knife for the functions you want. For example, you may want a tanto, but are willing to sacrifice some of the point strength for control and piercing ability. Having read the FAQ, you know you can clip the point (controllability) and thin the edge via a false edge (piercing ability), which is exactly the approach Benchmade took with their Stryker. Or if you want your tanto to slice a bit better, you can make the straight edge slightly convex to simulate a belly -- the approach taken by Microtech on their SOCOM tanto. By mixing-n-matching, we can enhance a design's strengths or sacrifice a little to make up for a deficiency somewhere else.
With that in mind, let's briefly examine some popular knife designs, and see if we can figure out why the designers made the choices they did.

Combat/Utility Knives

The Marine Corps' kabar combat/utility knife is a classic. It's a clip point design, with a false edge that is sometimes sharpened. This makes the point very sharp, and easy to control in thrusts. As with most clip points, there is a nice belly for slicing. This makes it suitable for fighting and utility uses.
The grind chosen was a sabre grind. This makes the edge very strong, but sacrifices cutting ability (versus a flat grind). In theory, the sabre grind might have been chosen because of the very hard use and abuse this knife may go through, not just as a knife but as a pry bar or hole digger. At least as importantly, the sabre grind is faster and cheaper to produce than a flat grind, important when many knives have to be turned out.

The Mad Dog ATAK takes a different route, going with a thick spine and flat grind, but retaining the clip-point format. The flat grind means the edge will outcut the kabar, and the thick spine helps assure robustness for hard use (as does the differential heat treatment). A positive included angle (also discussed above) enhances chopping and slicing performance. Sort of a high-performance version of the standard combat/utility knife, more expensive to produce but outperforming the standard in just about every other category.

The Camp Knife

Camp knives are generally big, 8" or more. They're almost always flat ground, for good edge performance. The job of this kind of knife is to do camp chores, from chopping limbs to splitting kindling to food prep to anything else. The flat grind provides great performance, and the usual clip- or drop-point format provides point control when needed. Size and weight is needed for chopping effectiveness.

Three Folders

The tactical folder craze has spawned many folders with sabre grinds, and that emphasizes strength over cutting ability. But there are a few folders that consistently do very well in cutting tests.

The Sebenza had a straight clipped point, for excellent control, and plenty of belly. A very high hollow grind provides a thin edge, for great push-cutting and slicing.

The AFCK has a sabre grind, but still performs wonderfully. The blade is relatively thin, so even with the sabre grind the edge remains fairly thin and performs well. In addition, the blade is at an angle to the handle, providing even better slicing and slashing performance. The straight-clipped point is very sharp and controllable.

These two folder makers have made different design decisions, but both have achieved excellent results. The main objectives -- a working point, a belly, and a thin edge -- are achieved through different designs.

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The Microtech SOCOM tanto is another design worth examining. It is ostensibly an Americanized tanto. However, the designers have made a large number of interesting tweaks to enhance the design. First, for point control, the point is clipped slightly and the blade meets the handle at an angle -- both of these things bring the point in-line for control. To make the point a better piercer, the front bevel is at a much smaller angle to the point than is normally seen. The normally straight edge is slightly curved, and combined with the low-angle front edge, the secondary point ends up not very sharp. So this is a tanto with a bit of a belly, and combined with the blade/handle angle, functions well as a slasher/slicer. Lastly, Microtech ground in false edge bevels on the spine, which disappear near the point. This leaves the point full width for strength, but removes some weight (and adds good looks) along the spine.

A Hunter

A.G. Russell's Deerhunter is a drop-point format, and is flat ground like many hunters, to provide a thin edge that cuts exceptionally well. To improve the geometry even more, the spine is <.125", making the entire package extraordinarily thin. As a result, the knife wouldn't be a great choice for prying, but for slicing and push-cutting it is outstanding.

A Custom-Made Folder

To show the kind of tweaking that can be done, I will describe a custom folder I had made for me by Allen Elishewitz. The blade has the dual-grind of a tanto. That is, flat grind up front near the point, hollow grind along the straight edge. However, this knife is not a tanto, it is a drop point. So this knife has the tip strength of a tanto, but the useful belly of a drop point, and a dropped point for better control. In addition, the point has false edge bevels ground in, which makes it penetrate a bit better. In short, we took the massive point strength of a tanto, but ground it on the more useful utility shape like a drop point, then ground in bevels to make piercing ability a bit better. Tweak and tune!

LINERLOCK TESTS

Liner Lock Tests, by A.T. Barr and Joe Talmadge

A well-made liner lock is a beautiful thing. The action is smooth, the lock is very strong, and it can be opened and closed one-handed. However, it is easy for the knifemaker to make a mistake on a liner lock. Many common mistakes can result in the lock accidently unlocking, and this is a serious threat to fingers. Below are some of the tests we recommend a potential buyer try on a liner lock. Keep in mind that many of the factory knives easily pass all the tests below, while many knives from custom makers -- including those lauded in the knife rags -- often don't pass. Test your knives, don't assume the more expensive knife has the more secure lock-up!

One caveat is that the second of A.T.'s suggestions, the "palm-on-spine" and "whack-the-spine" tests, are a bit controversial. We both feel that a blade should never close due to palm pressure, and a moderate whack on the spine shouldn't make a blade fold up either. Some makes say that a knife in normal use does not ever get whacked on the spine, so this test is not real-world. You can decide for yourself how secure you think the lock should be.

A.T. Barr's tests

You don't want your blade to open except when you want it to. Always check for a good detent ball to blade tang contact. Open your liner lock normally and then close it very slowly. The blade *should* snap closed the last 1/16" or so.

Open your knife blade very slowly, until the lock engages. Do not snap it open. You want the tension of the liner lock to just snap to the tang of the knife. Then do two things. First turn the knife over, and using the palm of your hand try to close the blade. It should not close. Then strike the blade spine on the table. Not real hard, but it needs some pressure. It should not close.

Snap the blade open REAL FAST, then close it. If it takes a lot of pressure to unlock the blade, walk away from that knife. Open the knife blade real slow, and check for any movement. Sideways or up & down.

Great tip

Also, if your liner lock has a sloppy lock-up, sometimes you can help it by snapping the blade open and then half-way hard striking the blade (try to close it) on it's tang. That will help seat the Titanium liner to the tang of the blade. If that does not work, send it back to the maker. Be careful when you do this. If the blade does disengage, the blade will hit your knuckle. A number of rec.knife readers have reported good results using this tip.