The Razor's Edge
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Nothing beats a knife in the bush. You use it to bleed your kudu, skin it, cut biltong, trim riempies and clear away branches for your shooting lane. In the bush you need a knife that is efficient - and it can only be at peak performance when it is really sharp
Your knife will get dull with use, so you need to sharpen it so we tried a whole bunch of sharpeners, many of them junk or not just not made for Africa.
We quickly eliminated electrical sharpeners, the drag-through type (which removes a small sliver of steel and various other devices that can not create a double bevel.
Our criteria was a razor’s edge - functional, consistent and easy to repair - in the African bush, far away from electricity and paid sharpening services. We did not want a super-fragile shaving edge - you are here to hunt, not to make a advertisement for men’s cologne. We also wanted a system that you can use at the Mopani fire at night while quietly chatting and sipping your Cabernet Sauvignon, something that was easy to use, reliable and did not weigh our daypacks down.
We eliminated all but 2: The Lanski Sharpening System and the locally manufactured Warthog Classic II Sharpening system.
First, some basics
Several things - blade thickness, blade shape, edge angle, edge thickness and edge smoothness will determine the cutting ability of your favourite hunting knife.
Blade thickness has a great effect of slicing ability. Because of the thickness of the blade, your hunting knife will never slice like a the thin blade of a filet knife - no matter what you do to the edge.
Blade shape is determined by the function. More belly or curve is typical of a skinning knife and the straighter edge of filet knives are designed for slicing.
We wanted to choose the correct to choose the correct edge type for a hunting knife.
Here are the options:
The simplest and most widespread in factory knives. The edge tapers from both sides of the blade. Sharp but sacrifices durability. The sharp transition point induces extra drag.
Provides the most durable edge at a given angle and has less drag compared to other edge grind types due to smooth transition lines.
Instead of tapering in a straight line, the edge is slightly curved outwards. The famous Japanese Samurai katana used this type of the edge.
3. Asymmetrical Semi Convex
Combines durability of the convex edge and ease of sharpening of the flat edge, until the edge gets real dull.
4. Asymmetrical Flat
The edge tapers on the straight line from both sides, but the angles are uneven. Used for more durable edges but sharpness is sacrificed.
5. Compound or Double Bevel
Cuts better than a flat edge at the same angle as the secondary bevel, yet lasts longer than a flat edge if ground at the same angle as the primary bevel.
Provides a strong, durable edge but sacrifices a degree of sharpness.
The edge contours are concave, resulting in a very sharp edge with low durability. Extra drag is induced due to the shoulders and sharp transition points.
The edge is flat from one side, tapers on the straight line from the other side of the blade. This is the sharpest edge, found mainly on chisels in western world.
The Japanese use the chisel edge widely in their kitchen knives.
8. Chisel with Back Bevel
This variation of the Chisel edge. Back side has a micro bevel, usually at a very low angle of 3°-5°. Some sharpness is sacrificed for increased edge durability.
9. Chisel with Urasuki
Urasuki is traditionally found on Japanese single beveled knives. Back side of the blade is concave to reduce the drag during cutting.
Serrations help with cutting by letting the edge attack repeatedly from different angles with varying pressure.
Serrated edges are useful for cutting food and rope – but for a hunting knife you need a plain edge.
The Best edge in the bush
In the bush you need:
A method to quickly and easily resharpen: that means precise replication of blunted cutting edges
The compound bevel is the only edge which provides all that is required.
Factors that affect efficient cutting
Edge angle is measured between the center of the blade and the bevel or flat cut by the sharpening surface. Most Western knives are double bevel.
Asian knives and woodworking tools are single bevel, and the resulting smaller angle can make them aggressive cutters. That is why sashimi knifes seem so sharp.
Any edge thickness under a few thousandths of an inch may be considered sharp. Paper is about 2 to 3 thousands of an inch thick - but it and will cut you if conditions are right.
Edge thickness naturally increases with wear.
Ideally, the cutting edge would come together to make a perfect edge with zero edge thickness, but edge thickness is limited by several factors.
First is malleability, or the tendency for steel to move when it is pushed. The yield strength of steel is thousands of pounds per square inch, but as the edge thickness approaches zero, it takes only a fraction of an ounce to move it. The force of your hand with a stone or steel can move enough steel to create or smooth a burr.
The second limit to edge thickness is edge smoothness. You can’t have a 1/10,000-inch edge if you have scratches 1/1000 inch deep. The grit of the cutting stone determines scratch pattern or smoothness. Good edge smoothness requires careful work with your finest stone
To be sure you are improving your sharpening; you need an objective way to test the results. Tests evaluating sharpness range from cutting silk to chopping trees. What you need is a test method that is useful for you.
Most people test an edge by rubbing their thumb lightly across the edge and feeling how the edge grabs as it tries to cut into the thumb pad. To keep your thumb calibrated, test a known sharp edge like a new razor blade periodically.
Shaving hair on your hand or arm is another common sharpness test. Shaving sharpness can be achieved even on heavy hunting knives or an axe. Razor sharpness is only possible with both a polished edge and a small edge angle.
Although you will look as cool as Crocodile Dundee, testing by shaving can be misleading if the blade has a burr or wire edge. Steel naturally forms a burr - a thin bendable projection on the edge - during the sharpening process. A blade with a burr will shave but will not stand up to hard use. To test for a burr, slide your fingertips lightly from the side of the blade over the edge. You will feel the burr drag against your fingers. Test from both sides, because burrs are usually bent over one way or the other.
Another test for sharpness is to press the edge lightly on your thumbnail at about a 30-degree angle. If it cuts into your nail it is sharp and if it slips it is dull.
The sharper the blade, the smaller you can make the angle before it slips. Try this with a new razor blade to see how a really sharp blade feels. The down side of thumbnail testing is that the little cuts in your nail get dirty and look bad until the nail grows out. For this reason some people do this test using a plastic pen or pencil.
As your sharpening improves you will be looking for smaller and smaller burrs.
The glint along the cutting edge means a dull blade. Many good sharpeners have learned to see a dull edge. Hold the blade in front of you with the edge in line with a bright light. Move the blade around a bit. A dull edge will reflect a glint as do nicks and burrs.
A sharp edge does not reflect glints.
The only tool available for edge testing is the Edge Tester from Razor Edge Systems. The Edge Tester evaluates edges on a 100 point scale for sharpness and smoothness. The principle is similar to the thumbnail test, but the Edge Tester has a special material and shape for repeatable testing.
If you’re serious about sharp knives, get an Edge Tester.
The most effective test?
All these tests (apart from the Edge Tester) are very subjective.
We use another way to test sharpness.
A better test
We measure the amount of force it takes to cut through a loop of thread. Repeated tests of this type give data that can be evaluated using statistical methods.
For each test a loop of thread is tied and suspended from a small scale. The blade is placed inside the loop and pressure is applied against the thread.
The maximum force before the thread is cut indicates the sharpness of the blade, with smaller numbers reflecting a sharper blade.
Steeling and Stropping
Steeling is swiping the cutting edge against a steel rod - also called a steel or a butcher’s steel – to realign the cutting edge.
How to do it
Hold the rod vertically and swipe the knife along it, as if you are making a cut. They key is to try to match the angle you are holding the knife at to the same angle as the edge angle.
Using a magic marker will help. Cover the cutting edge with the marker and make a swipe or two. Wherever the marker is gone that’s where you are hitting the edge.
If you are doing everything right, then all you need is 3-5 passes per side to realign the edge.
Stropping is a necessary and effective step after any sharpening.
Stropping serves the same purpose: aligning the cutting edge by it on a piece leather. Stropping normally is done on the plain leather, however coating the leather with an abrasive compound such as diamond paste or chromium oxide powder will make a fine sharpener.
Hard steel (above 62-63HRC) doesn’t respond well to stropping on the plain leather. Borosilicate or ceramic rods are effective on very hard steels.
How to do it
Stropping is done in the opposite way of steeling: the edge is dragged backwards, not pushed forward. Use very light pressure and try to match the edge angle. Again, a magic marker will help with the correct angle.
If you have not done it before, try it: your sharpening results will dramatically improve.
The Ultimate Sharpening Method
Your new knife is sharp, but ...
Your new knife will be sharp, but you need to be able to keep it sharp.
The best sharpening system in the world won’t give you a sharp edge until you create a relief, which is the base edge for a sharp blade.
All sharp knives and razor blades have at least two edges, the relief and the secondary edge. Failure to put both of these edges on a knife is a major reason for sharpening failure.
Figure 1 shows an exaggerated cross-section of a typical knife as it comes from the factory. There is no relief and a secondary edge is ground into the edge of the knife. Each time you sharpen the secondary edge the knife will become blunter.
What is required is to create a relief. It should have a minimum width of 1/16" but it can be much wider. You can hone the relief all the way back to the edge of the knife if you want to remove that much metal. Start with a relief angle of 13°.
Since your relief has such a small angle, the edge of the blade will be weak and become blunt easily. We will take care of that later when we add the secondary edge.
Step 1: Create the relief
Set the angle at 20°
Use the 280 grit hone (green)
Hone until you feel a burr as shown in figure 2. You probably won’t be able to see the burr but you will be able to feel it on the side opposite from the side you are busy honing as it bends in the opposite direction. You can feel the burr by dragging your finger across the bottom edge of the knife blade. Steel naturally forms a burr - a thin bendable projection on the edge - during the sharpening process.
Make sure you have a burr running the entire length of the blade. Don’t continue to the next step until you have the burr.
Continually wash the honing device with plenty of water to remove the sludge. Sludge will dull the knife while you are trying to sharpen it.
Flip the knife over and grind until the burr
runs the entire length of the opposite side.
Turn the knife over and choose a medium grit.
Hone until you get the burr.
Flip the knife over and hone the burr away on the other side.
Set the angle at 20°
Hone until the angles meet at the cutting edge. Check for the telltale shiny edge at the cutting edge which shows that the edges do not yet meet.
With the Warthog System, both sides of the blade are honed at the same time and burrs are much smaller.
Step 2: Create the Primary Edge
Change to a 600 grit (green) and set the angle at 25°
Hone until the angles meet at the cutting edge - about 20 times.
With the Warthog System, both sides of the blade are honed at the same time and burrs are much smaller.
Step 3: Strop or steel
Lightly stroke the knife edge approximately 5-19 times on each side using a ceramic steel rod or a leather strop.
Unclip and flip the rods so that the finishing steels are facing upward and increase the angle of attack to 30°. Pull your blade through another 10-50 strokes.
You have just created a durable, sharp, bevel knife edge - and it is probably sharper than any knife you have ever handled.
Also, the angle of the primary edge will insure that the knife will remain sharp long after most knives have become dull
The face off
We tested 2 great devices which work in African hunting conditions: the proven Lanski system and the newer Warthog Sharpening system.
Here is what we found:
Lansky has been making various sharpening systems for years. We tested the Standard 3-Stone System with Alumina Oxide & Ceramic which includes coarse (120 grit), medium (280 grit) and fine hones (600 grit)
Angles of attack are 17, 20, 25 and 30 degrees.
Light and small
Relatively quick and easy to use
The standard kit is not supplied with a mount as standard equipment (a $5-$20 option), so you must sharpen your knife while awkwardly holding the clamp in one hand.
Because of the clamping mechanism being set so far back on the blade, it is possible to apply too much pressure on the hone and pushing the blade edge down . This results in a change of the honing angle without you knowing about it - the result is unintentionally using a different sharpening angle.
The clamping system has a very small lip one tenth of an inch (2.5 mm). In thicker blades the clamp tends to be unstable.
On long blades, the clamp has to be moved closer to the point to maintain the same angle of attack on the edge. Angle change can be 1.16° over 3.5" (9 cm). The clamping system tends to let the knife slide out on longer blades
As stones wear, they become hollow and the altering the angle of attack changes constantly during every sharpening stroke
The V-Sharp Classic II is a well designed product that is very quick, accurate and easy to use. A constant angle can be maintained while sharpening freehand and the blade guide is easily adjustable. Angles of attack are 17, 20, and 25 degrees.
Coarse (325grit) and medium (600) diamond hones are standard. Fine (1000grit) diamond honing pads are optional.
Included as standard issue are high carbon steel wire forms used to steel the edge.
Easy angle of attack adjustment
Angle of attack remains constant whatever blade length
Both sides of the blade is sharpened at the same time
Burrs are smaller or nonexistent
Heavier than the Lansky
A close-run thing between two excellent sharpening devices with Lansky at 114 and Warthog at 124, but the results show the best sharpener for Africa is the Warthog. Visit their web site atwww.warthogsharpeners.co.za
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