Sharpening a knife is not difficult to do, but some practice is required to obtain the very sharpest edge your knife is capable of. Putting a keen edge on a knife is a process affected by a number of variables. Some of these variables include the sharpening system being used, the blade steel, the condition of the knife and the experience of the user.

Personally, I recommend using one of the sharpening systems that clamps and holds the knife blade in a fixed position while a hone is moved across the blade at a predefined angle. The Lansky sharpener is the most well known of these systems, although there are numerous variations available. The benefit of this system is in the consistent angle that may be obtained for each stroke of the hone and allows a novice to sharpen a blade to a very fine edge.

Typically these systems will have at least 3 angles of cut to choose from. Your choice would depend on the type of knife or tool being sharpened. The Blade Master system I use has 4 angles: 15, 19, 24 and 29 degrees. As the number increases the angle becomes more shallow and cuts a finer, although thinner, edge. The thinner the edge the sharper the blade will be. However an angle of 29 degrees is so shallow that it should be used only for fine kitchen knives with very thin blades. As the number decreases the angle becomes steeper and sharpens the blade to more of a chopping point. Obviously a thin edge will not stand up to rough use such as chopping or aggressive cutting and the smaller angles should be used here. In general, a daily carry knife will be best sharpened at a 19 degree angle or thereabouts.

To sharpen, the user clamps the knife in the holding device and beginning with a coarse hone, strokes are made on each side of the blade to remove enough material to reset the edge. Finer hones are then used in the same way to refine and polish the edge.

Another popular knife sharpener is exemplified in the many "pocket sharpeners" that are on the market today. These sharpeners will often have a pair of sharpening rods, usually made of ceramic or similar material, that are fixed into a handle at a predetermined angle to form a "V". There is no angle selection possible with these systems. To sharpen, the user simply holds the sharpener in one hand, puts the knife blade into the "V" shaped slot made at the cross section of the two sharpening rods and pulls rearward in a reverse stroke. As the blade moves along the bottom of the V, the rods sharpen the blade to the angle at which they are set. These systems are useful for a quick touch up in the field, but I would not use them as a mainstay for blade care as the angle can change according to how the knife is held while stroking, the sharpening rods cannot be adjusted, nor is there any choice in the grit of the hone.

Wetstones have been used longer than any other method and do work well, although they require practice if sharpening freehand. In this method there is no assist with the cutting angle or maintaining the angle through the sharpening motion, the sharpening surface is the only offering. Here, a user must hold the blade at an angle believed to be correct and moves the blade across the hone in a forward shaving motion, as if trying to shave off a thin slice of the stone. Swirling movements are sometimes employed and once sharpened the blade is turned over to repeat the process for the other side. The danger here is twofold. First, the angle being sharpened may not be the ideal angle, nor is it likely this angle can be consistently maintained through the freehand movements of sharpening. In the end, the knife will usually be sharper, but will not have the consistency of a clamp system. Doing a poor job with a wetstone can actually make the blade worse, which is why this method is best reserved for experienced users. Sometimes a wetstone system will come with a clamp device that holds the blade at a consistent angle while moving across the stone. This helps greatly in achieving a proper edge.

The blade steel will also have an impact on the edge sharpness and retention. As a general rule of thumb, chromium is added to steel to increase the stainless properties but this can also have a detrimental effect on the ability to achieve a top flight edge. The higher the Carbon content of the steel, the better the edge it will take, but is also more susceptible to discoloration. Premium knife steels such as the Sandvik steel, ATS-34 and 154CM are formulated for the best of both worlds. Other lesser steels will experience trade off between these two extremes.

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