Tuesday, August 09, 2005
Knife Sharpening
Sharpening
Knives are sharpened by grinding against a hard surface, typically stone. The smaller the angle between the blade and stone, the sharper the knife will be, but the faster it will dull. A guide is very helpful.
Very sharp knives sharpen at 12-15 degrees. Typical knives sharpen at 22 degrees. Knives that chop may sharpen at 25 degrees. In short, the harder the material to be cut the higher the angle of the edge.
The composition of the stone affects the sharpness of the blade (finer grain produces sharper blades), as does the composition of the blade (some metals take/keep an edge better than others).
Examples of sharpening tools are the clamp-style systems, which use a clamp with several holes with pre-defined angles. The stone is mounted on a rod and is pulled through these holes, so that the angle remains consistent.
Another variant is the crock stick setup, where two sticks are put into a plastic or wooden base to form a V shape. When you pull a knife up the V, the angle is held for you, as long as you hold the blade perpendicular to the base.
Remove a wire edge (burr) if one forms during sharpening. Use a slighly steeper angle with very light pressure to do so. If not removed, it will break off in use, and the knife will instantly become dull.
An alternate method of removing a wire edge is stroking from side to side on a very fine stone, using light strokes. This will flip the burr back and forth as it is ground off.
To feel for a wire edge, move your thumb lightly across the edge. It should come off with no resistance. If you feel a little bit of pull at the edge or the nail is sightly abraded, you may have a wire burr.
Honing stones (also called whetstones) come with coarse and fine grits and can be hard or soft describing whether the grit comes free. Arkansas is a traditional source for honing stones, which are traditionally (though a poor practice) used with water or honing oil. India is another traditional source for stones.
Ceramic hones are also common, especially for fine grit size.
Water stones (both artificial and natural) come in very fine grits. They are stored in water, and develop a layer of slurry which dulls the edge if you hone the blade as if honing into the stone. Generally, these are more costly than oilstones. Oil is not to be used on these.
Oil is sometimes used to lift the metal dust, called swarf, off the stone. This is generally bad to do during polishing. There are better ways than oil to clean a hone.
Coated hones, which have an abrasive, sometimes diamonds, on a base of plastic or metal are another kind of hone. Rather expensive, are sharpening blocks made with corundum.
Stropping a knife is sometimes a finishing step. This is traditionally done with a leather strap impregnated with abrasive compounds, but can be done on paper, cardstock, or even cloth in a pinch. It will not cut the edge significantly, but produces a very sharp edge with very little metal loss. It is useful when a knife is still sharp, but has lost that 'scary sharp' edge from use.
Other times the final step is done with a steel. This fine process can effect alignment of the edge. Realigning the edge goes a long way in keeping the knife sharp, as often times, a rolled edge will make an otherwise sharp knife dull.
I personally use a Diamond plate that is 2 inches x 6 inches in size and has a grit of 600. For my own personal application I have found this best and the quickest method.
Teddy
Knives are sharpened by grinding against a hard surface, typically stone. The smaller the angle between the blade and stone, the sharper the knife will be, but the faster it will dull. A guide is very helpful.
Very sharp knives sharpen at 12-15 degrees. Typical knives sharpen at 22 degrees. Knives that chop may sharpen at 25 degrees. In short, the harder the material to be cut the higher the angle of the edge.
The composition of the stone affects the sharpness of the blade (finer grain produces sharper blades), as does the composition of the blade (some metals take/keep an edge better than others).
Examples of sharpening tools are the clamp-style systems, which use a clamp with several holes with pre-defined angles. The stone is mounted on a rod and is pulled through these holes, so that the angle remains consistent.
Another variant is the crock stick setup, where two sticks are put into a plastic or wooden base to form a V shape. When you pull a knife up the V, the angle is held for you, as long as you hold the blade perpendicular to the base.
Remove a wire edge (burr) if one forms during sharpening. Use a slighly steeper angle with very light pressure to do so. If not removed, it will break off in use, and the knife will instantly become dull.
An alternate method of removing a wire edge is stroking from side to side on a very fine stone, using light strokes. This will flip the burr back and forth as it is ground off.
To feel for a wire edge, move your thumb lightly across the edge. It should come off with no resistance. If you feel a little bit of pull at the edge or the nail is sightly abraded, you may have a wire burr.
Honing stones (also called whetstones) come with coarse and fine grits and can be hard or soft describing whether the grit comes free. Arkansas is a traditional source for honing stones, which are traditionally (though a poor practice) used with water or honing oil. India is another traditional source for stones.
Ceramic hones are also common, especially for fine grit size.
Water stones (both artificial and natural) come in very fine grits. They are stored in water, and develop a layer of slurry which dulls the edge if you hone the blade as if honing into the stone. Generally, these are more costly than oilstones. Oil is not to be used on these.
Oil is sometimes used to lift the metal dust, called swarf, off the stone. This is generally bad to do during polishing. There are better ways than oil to clean a hone.
Coated hones, which have an abrasive, sometimes diamonds, on a base of plastic or metal are another kind of hone. Rather expensive, are sharpening blocks made with corundum.
Stropping a knife is sometimes a finishing step. This is traditionally done with a leather strap impregnated with abrasive compounds, but can be done on paper, cardstock, or even cloth in a pinch. It will not cut the edge significantly, but produces a very sharp edge with very little metal loss. It is useful when a knife is still sharp, but has lost that 'scary sharp' edge from use.
Other times the final step is done with a steel. This fine process can effect alignment of the edge. Realigning the edge goes a long way in keeping the knife sharp, as often times, a rolled edge will make an otherwise sharp knife dull.
I personally use a Diamond plate that is 2 inches x 6 inches in size and has a grit of 600. For my own personal application I have found this best and the quickest method.
Teddy
