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Sharpening

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Everyone who does so has their own way of doing this. Here's mine.


I sharpen for the following reasons

The blade behind the edge is too thick.
The shape of the edge itself is no longer optimum, it has flats, chips, or is rounded off.
The edge is weak and has bent over such that it will not cut well.


I use the following tools to sharpen

10 inch wet wheel grinder.
Carborundum dual grit, 8 inch, hand stone.
A strop or the palm of my hand.


Sharpening generally begins with an examination of the edge under a bright light or sunlight to determine the nature of the problem and arrive at a satisfactory decision as to the remedy. Any flats, dings or rounding out of the edge becomes immediately apparent as a truely sharp edge does not reflect light whereas a dull edge does.

I use the wet wheel to correct a thick edge or take out large chips and dings. I always sharpen against the direction of rotation as if I were trying to cut a slice off the stone. Kinda like I want to peel an orange. I don't pay much attention to the angle I am using. If I need to remove the material I just throw all caution to the wind and grind, so I use what ever angle is required. I don't use a whole lot of preasure but I do use more preasure than I ordinarily might. Bending the edge is not likely at this stage as its plenty thick and strong and besides, I'm really working behind the edge not on it. If my stone is not cutting fast enough then I need a coarser stone. I stay out of the ridgeline area unless absolutely necessary as large scratches up there will be hard to get out later. I don't worry about getting scratches on the lower part of the main bevels. If the knife needs it I grind away like no tomorrow and trust to polishing everything out later if need be. When I am done I go to the coarse handstone to clean up the scratches made by the wet wheel and refine the shape further, flattening amd smoothing as need be. I could use a coarse handstone to do the whole thing from start to finish but it takes longer.

Grinding primary bevels like this is more akin to stock removal than sharpening but is briefly included here because every now and then one comes across a knife that really needs it.

Lets assume that the blade is properly crossectioned for its intended task and that our examination of the edge reveals that it is simply very worn and unsharp or just a bit dinged up. For heavy work I will start on the coarse side of the stone. I hold the stone in my left hand and the knife in my right. Again I behave as if I am trying to take a slice out of the stone. The edge leads, the spine follows.

Generally I will hold the knife at something approaching a 10 degree angle to the stone, making for a 20 degree included angle at the edge. You can repeatedly fold a piece of paper to get an idea of what 11 (22 included) degrees looks like. Choice of angle will vary plus or minus a few degrees depending on the kind of knife and the materials I anticipate cutting with it. If I want to shave with it I sharpen with the knife flat on the stone. Around 7 (14 included) degrees works well for meat. Harder materials such as soft metals can be cut at around 15 (30 included) degrees and even thin sheet steel such as that found in tin cans, may be cut at 20 (40 included) degrees. However don't be surprised if you damage your knife edge, cutting steel or even soft metals.

The background sound on this page was made with a hand stone and a tanto. I work only in alternating strokes, first one side of the blade then the other, turning the knife over each time. I don't use a lot of preasure on the stone, if its a good sharp stone and its coarse enough I don't need to. Every now and then I stop and examine the edge under a bright light to see if my bevel's are running all the way up to it. The old edge gradually begins to disappear and soon I can not see any reflected light from it at all because a truely sharp edge is not visible to the human eye. This notion is not a new one, as William Shakespeare says in Loves Labor Lost, "Keen as is this razors edge invisible". When that happens I know that the edge is pretty sharp however it may not be cutting well yet. This is because I have done all the work so far with the coarse side of the stone.

Now I need to refine that edge so I turn the stone over to the fine side and continue as before. I do not change the angle and I continue to alternate. Gradually the coarse scratches made by the previous stone give way to a smoother satiny appearance indicating that the surface is more refined. By now the edge is on the verge of shaving arm hair so I begin to ease up on the pressure even more until only the weight of the knife is bearing on the stone and continue for a while longer. Soon the knife will shave.

You may notice I make no mention of lubricants when using handstones. Thats because I don't use them. Lubricants are designed to minimise wear which is somewhat counter productive to the desired outcome. Handstones generate insufficient heat to warrant coolant or lubrication.


I will strop a knife on the palm of my hand or a leather if I feel it warrants it. In this case the spine leads and the edge follows. At the end of each stroke the knife is rolled over on its spine and stropped in the opposite direction. Mostly I will skip stropping as the knife is already shaving sharp but some knives seem to like a polish to really make them perform at their best.The strop is a leather strip affixed to a wooden block and loaded with abrasive. Ideally a different strop is used for each grit size. If used in conjunction with a fine abrasive it is very usefull for maintaining an already sharp edge in optimum condition. Once it no longer effects an improvement the knife is returned to the fine grit stone for redressing. This is a very economical way to maintain an edge as the strop removes very little material at a time.

 

Sharpening
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