Browsing: Hunting Knives

Blade Edges

Testing for Sharpness

First, I checked for sharpness. It is commonly known that some ultra-0smooth edges will slice through non-fibrous materials better than fibrous ones. But if you think about it, even a piece of meat has fibrous tendons in it. Many vegetables can also be quite fibrous. I needed to find a test material that would be fibrous in nature but still require an extremely sharp edge to cut cleanly. There are many different ideas on the best was to check for sharpness. Some are better than others. At the fore font of sharpness checking demonstrate the sharpness of edges. The main problem is determining and quantifying how easily the edge shaves. Also you end up using more of a shearing cut than a slicing one. Remember, all the edges in the photos will shave hair easily. Slicing paper is also used as a test of sharpness. Most papers are very easy to slice smoothly, but a few delicate papers such as cigarette and onionskin papers are much more difficult.

Several of these papers also seem to be directional in the orientation of the fibers, making them easier to cut in one direction than the other. I tried several brands of paper and found that Zig Zag seemed to be the most consistent and the most difficult to cut across the short dimension.
As I started slicing paper, my misconceptions started surfacing. I had always thought that the smoother that edge was, the better it would cut- period. At a hardness of 58.5 HRC all the edges except D and F would slice the cigarette paper across the short dimension. Just as I had expected, it was most difficult with A, easier with B, easier yet with C and E, but been impossible to verify that all the teeth had been polished off without a microscope. The few teeth left on the edge would allow the blade to start the cut in the paper. That in turn, would mislead me into thinking that the stopped edges both sheared a sliced better than those having a tooth. The real problem with my theories started to come out when I started to look at how the edges wore. Here things can get very complicated.

Testing for Edge Wear

I sliced through corrugated cardboard for my wear tests. I used it because it was cheap, consistent, and available and dulls edges fairly quickly. I used a slicing type action to get through the cardboard instead of shearing it. Slicing is how most knives are used in the real world and dulls a knife faster than shearing. I sliced up 1x 2 squares with each edge finish and then examined them under the microscope. As I expected, edge A cut with the most difficulty while wearing to a larger sharply-toothed edge. It would still shave with difficulty but not cut the paper. B wore to something resembling A, after the same amount of cutting. The larger teeth had sharp edges and were not rounded off. Shaving was quite easy and it would still barely cut the paper. Then it happened. Edge C wore to something resembling edge D and would barely shave at all. Trying to cut the paper was like a bad joke. Remember, this was all done with the same blade.

Then, edge D wore to an edge that still looked like D but with a slightly rounded edge and no shaving at all. Something had happened between edges B and C. So now I had a problem. I thought the problem might be hardness, so I re hardened the blade and left it at 60.0 HRC. Then, the edges performed more like I would have expected. All the edges wore to a coarser tooth, except for D, which still rounded off. Edge C cut so well that I had slice up two additional pieces of cardboard before I started to notice any significant wear. When it did wear this time, it went to a coarser tooth with sharp edges. I was surprised that a hardness difference of only 1.5 HRC would make such a change.


I also did a little testing with a factory stainless. The tests were performed quickly as I was running out of time and only wanted to get a general idea of what was happening. The most important result was that all the edge finishes seemed to wear to a round smooth edge instead of a sharp, larger tooth. Another variable not even considered here is the actual angle at the edge. I am sure that varying the angle will affect the changeover point between the edges that wears to one having sharp teeth or one that becomes smooth. As you can well guess, my lecture at the seminar was a little fragmented and without a great deal of detail. The good part was that I learned a lot and have a completely new direction to explore.

Current Practice

Currently I am sharpening all of my blades to the finest tooth edge I can get that will not wear smooth. If the edge is continually wearing to a coarser tooth having sharp edges, the effective useful life of the edge is increased. If the edge is just rounding off, the useful life will be very short. For most of my steels and Damascus I am finishing with an Ultra Fine grit Spyderco stone. The blade hardness is usually about 60.0 HRC. You might think that 60.0 HRC is too hard and brittle for a blade. I salt bath mar temper and freeze my blades in liquid nitrogen, thus reducing the brittleness problem greatly but, that is the subject for another article. I have eliminated all leather stropping with compound.

A light strop on denim is used to clean the junk out of the teeth formed by the stones, but I want to leave the micro teeth in place. If I have the opportunity to make a knife that will only cut fleshy materials and never anything fibrous, I will consider stropping and polishing the edge. Please remember that these results are only preliminary. Different knives on a different day might show entirely different results. I have a great number of samples to make and tests to run now. This winter I will be running tests to try and figure out exactly what is going on. I will be including samples to investigate how steel choice, heat, treating, edge geometry and surface finish all affect sharpness and edge holding. If you have any comments or suggestions I would be glad to hear them. I am in many ways learning to sharpen all over again.

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Combat rifle (Knife)

The AK-47

The Ak-47 and its variations, arguably the world’s most popular military rifle with an estimated 70-milion manufactured, has recently inspired at least three heavy-duty folding knives. In “rifles of the world” John Walter states that, the Kalashnikov is simple, solid, reliable and surprisingly effective. The knives it inspired share those same characteristics. The knives include: Cold Steel’s Ak-47, Ernest Emerson’s Comrade M.F. and Boker’s Kalashnikov, which comes in three versions, old Steel registered the trademark “Ak-47 years ago. So that there would be no confusion, Boker, in October 2003, told its dealers that the name Ak-47 is trade marked by another cutlery company and cannot be used in the promotion of the Boker Kalashnikov line of knives. They asked that they not use Ak-47 in any promotions, advertising Web site use, or in any way to promote the sale of the Boker kalashnikov line. They also package an insert stating this with their Kalashnikov products. All three of these knives are beefy, and a real handful. Your father’s folding hunter they are not. The Cold Steel Ak-47 has a broad 4 inch clip-point blade and a 6 inch handle. Cold Steel literature states the weight is 7.6 ounces, the postal scales at my office state 7.2 ounces.

The Emerson Comrade M.F has a 3.9-inch clip point blade and a 5-inch handle. The weight is 5.2 ounces, making it the lightest of the trio. The size of the knife makes it seem lighter than it is. The Boker Kalashnikov has a 3 7/8 inch blade and a 5 inch handle. Weight is 5.9 ounces. The Cold Steel Ak-47’s large handle is crafted from thick bead-blasted air craft- aluminum scales that are bolted to steel liners mentioned in this article, and the scales are grooved to provide an even better grip. There is an ambidextrous pocket clip, and a unique feature is the pommelwith two lanyard holes. Cold Steel states that it is designed to be used as a less than lethal percussion tool for self-defense.

The Ak-47 has a Cold Steel’s Ultra Lock locking mechanism. A spring loaded sliding volt makes the knife as a bout as rigid as a fixed blade when open and also holds the blade shut when the knife is closed. I found the lock to be smooth secure and easy to operate one handed. Another feature is a thumb plate, which can be used for conversional one handed opening, or to snag the edge of a pocket for even quicker deployment. The knife is manufactured to Cold Steel’s rigid specifications in Taiwan, using carefully tempered and sub-zero quenched Japanese 8A steel. It was designed for Cold Steel by Andrew Demko. The Emerson Comrade M.F. uses a unique construction one handle slab is of 0.125 inch thick G10. The other, which provides a frame lock is of 1.8 inch thick titanium. On mine, the frame lock is by far the stiffest of that type I’ve encountered, no matter what the frame lock was constructed from. I’d say there’s no chance of accidental closure here. Ernest Emerson told me that the Comrade M.F. also known as CQC-12 was inspired, not by the Ak-47 rifle directly, but by the Ak-47 bayonet.

In Emerson’s 2006 catalog he elaborates “I have always admired the Ak-47 bayonet. I have used them for years in the field, usually to smash something open or pry something apart. Well, I final got around to designing a folding version.” One reason for his admiration may be that the Ak-47 bayonet has a practical clip-point blade that can server many purposes, rather than the slim spear point of most other bayonets. The 3.9 inch blade has a Bowie style clip point. It resembles the blade on Emerson’s CQC-13 Combat Bowie folder. One of the major differences I found between the Comrade M.F and the Combat Bowie was that the Bowie is a liner lock. Then there’s the price the Bowie is $239 retail, while the Comrade M.F lists at $395. Most Emerson knives have the Emerson Wave feature, a notch at the top rear of the blade that can be snagged on the edge of a pocket to pull the blade open. Once the knife is out of the pocket, it’s open and ready for use. Emerson was the first to come up with this method of opening, although I realized the same results several times by accidentally snagging an opening tab as I was pulling a knife from my pocket.

The Emerson Wave feature is now officially required on all knives Emerson’s company supplies to military combat units, military search and rescue units and law-enforcement agencies. Emerson uses 154 CM heat-treated to 57-59 RC, in his knives. The Emerson line is made in the U.S.A. Emerson uses the slogan “America’s Knife Company.” We are truly one of the last companies where the knives are 100 percent made in America. That means everything, including materials.

The Boker comes in three versions. While all are serial numbered, the top grade, with snake-wood inserts in the aircraft aluminum handle, is limited to 2003 pieces and evidently is aimed at collectors. Boker says they have exclusive rights from famed firearms designer Mikhail Kalashnikov to use his name on a knife line. As mentioned earlier, there are three versions in this series. The KALTD contains snake-wood inlays in the gray aircraft aluminum handle. The KALB is all black, with a black 6062-T6 aircraft aluminum handle and cocobolo wood inlays. The blade is coated with black PVD, a sapphire like material. Blades are clip-point, more elongated and therefore traditional than on the Ak-47 and Comrad M.F.

Best for users might be the basic KAL. It shares the same handle contours as the other Boker Kalashnikov knives. Designer Dietmar Pohl said that the contours as the other Boker Kalashnikov knives. Designer Dietmar Pohl said that the contours follow that of the Automat Kalashnikov-47 rifle. Inserts in the aircraft- aluminum handle are of black G10. A liner lock maintains blade rigidity when open. All the series feature blades of 440C. A ”Red star” with Kalashnikov’s name in both Western and Cyrillic covers the pivot area. The knives have pocket clips. The gift box has the appearance of a Kalashnikov clip. All there Bokers are made in Solingen, Germany.

 

I carried the Cold Steel Ak-37 and the Emerson Comrade M.F. for several days each. Both worked well in the bottom right pocket of cargo pants. Gowever, due its massiveness, tha Ak-47 rode most comfortably in a large nylon sheath I scavenged from the Tuckerman Knife by Colonial cutlery. I hope Cold Steel decides to offer an optional belt sheath for it. When it comes to price, the Cold Steel Ak-47 is by far the most cost-effective. Retail is $100. Emerson’s Comrade M.F. is the most-expensive at $395 retail. The three versions of the Boker Kalashnikov are $365(snake-wood), $265 (cocobolo) and $215 (G-10).

These three massive folding knives, while all different in, price appearance and locking mechanisms, have a common inspiration. And all promise to be as rugged and reliable as the gun that inspired them.

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