Convex Grinds PDF Print E-mail
Written by BuzzBait   
Sunday, 22 January 2006
 

While the Swiss Army Knife provides an excellent amount of outdoor utility, it is good to also carry a larger fixed blade on longer outings. Some of the best outdoor knives have convex grinds. The following information should prove useful in deciding whether a convex ground knife is right for you. The convex grind varies greatly from the factory grinds found on most modern day knives. Most of todayís factory knives employ various primary grinds, and a v-grind edge bevel. A convex grind can either be created on the edge bevel only, or combined as the primary grind of the blade. If the entire blade is convex ground, it is usually referred to as a full convex grind. A convex grind produces a very high performance edge on a blade, while maintaining a good amount of strength. It is almost the best of both worlds.

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While convex grinds appear to be an exceptional choice over todayís modern grinds, there are a few downsides to be factored into the equation. First off, convex grinds are a bit of a lost art, and require more highly skilled labor to produce. The actual edge bevel of a mass-produced knife tends to be an afterthought, with very little attention paid to it. A convex grind, especially when it is a full convex grind, must be done correctly at the point of manufacture. This raises the price of the knife. Another drawback to the convex grind lies in the area of aesthetics. To properly sharpen a full convex grind, one must remove material from the entire blade. This can create scarring of the blade finish, vastly reducing the visual appeal of the knife. And typically, a full convex grind requires a thicker blade stock than other knives, so a convex grind can add extra weight to a knife.  Lastly, few people know how to properly sharpen a convex grind. And if a knife is allowed to go dull, it is of little use to anybody.

Now, with the bad stuff out of the way, letís get into the advantages of convex grinds. Full convex grinds are extraordinarily simple and inexpensive to maintain. This may not appeal to those who rejoice in todayís plethora of sharpening gadgets, and who enjoy spending hours sharpening their knives. If a fully convex ground blade is not allowed to get too dull, stropping will usually restore the edge to full sharpness. You can buy an expensive stropping system, with a ton of mysterious stropping compounds, and have a ball when stropping your knife with these exotic materials, but you are not required to. An old mouse pad and a couple pieces of wet/dry paper will do the trick nicely. Yes, you heard me correctly. You can assemble a near perfect maintenance system with stuff you have laying around the house, or for only a few dollars cost. And when you compare your convex ground knife and simpe sharpening system to your friendís v-grind knife and expensive edge guide sharpening system, you will probably find the cost to be about equal. The difference is that you put your money into the important thing, the knife. Your friend has been forced to compromise on the quality of the knife, in order to afford to sharpen it correctly. Thatís no way to run a railroad!!!

Another advantage of the convex ground blade is shear cutting efficiency. A convex grind tends to act as a wedge, parting the material being cut, thus reducing friction or drag created by the material. Convex ground knives will tend to be much more efficient at deep cuts than knives with v-grind secondary bevels of similar thickness, with less binding on the substrate.

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Full convex grinds also tend to have a longer usable life. As one sharpens a flat grind, the thickness of the blade at the edge bevel becomes thicker and thicker as more material is removed. This thicker edge bevel will result in greatly reduced cutting efficiency. Because material from the side of the blade is removed when sharpening a full convex grind, the thickness of the edge is a constant throughout the life of the knife. A full convex grind will cut just as well after years of use, as it will when brand new. This factor is especially important to people whose knives are primary tools of their jobs or survival, as their tools require constant maintenance.

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 Okay. So letís get into how a convex grind should be properly maintained. As I stated before, the key is not to let a convex edge become too dull. Minor touch-ups are easily accomplished through stropping. Stropping with an abrasive compound or paper should also keep a nice satin finish on the blade, without the scarring created by using a bench stone. The diagram below shows a proper stropping motion on a hard abrasive surface. I illustrate this, as we do not always have a mouse pad or soft leather when stropping in the field. We often have to rely on our pant leg, smooth rock or board. The key is to draw the knife toward you, keeping constant contact with the blade as it is rotated. You want to abrade the entire side of the knife equally, and stop rotating as you hit the edge of the blade. You should feel a slight change in friction as you hit the very edge of the blade, telling you to stop rotating. This diagram can also be used when the blade becomes extremely dull, and you are forced to sharpen your knife on a hard bench stone, although some people prefer to reverse this motion, pushing the blade into the bench stone.

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When you do have the convenience of a nice soft stropping surface, maintenance is much simpler. Place a piece of abrasive paper on top of an old mouse pad or two, and lay the side of the blade on top. By pressing down, the pad and paper should conform to the shape of the blade, allowing you to make smooth, straight stropping motions. This can also be accomplished with a soft leather strop and polishing compound, in place of the pad and paper. The key is to have a thick and soft enough base, so that you donít have to rotate the blade. Typically, the grit of paper or compound you use, depends on how much blade material needs to be removed, and how finely polished an edge you prefer. As a rule of thumb, I normally start with a 600 grit piece of wet/dry paper, and finish off with 2000 grit paper. This produces a nicely polished edge, which is wonderful for push cutting. If I completely dull the edge of the knife, I'll start with as low as 220 grit paper.

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This article was shamefully stolen from our good buddy BuzzBait's original SOSAK site and I hope he doesn't mind us using it here. 

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This page tends to disappear from the 'net, wherever it gets posted, and I have had to track it down several times so I can refer to it.  I have copied it and added it to my site on 02/17/10, in the hopes of conserving it.  I have not been able to contact the original author for permission, although I give credit for his work.  Should anyone be able to put me in contact with him, it would be appreciated.

-Bill