If there were a Hippocratic Oath for knife sharpeners it would be the same as a doctor – “First, do no harm.” With proper use, cleaning and maintenance a high quality knife can last you the rest of your life.
Those of us who sharpen knives for a living come across some pretty beat up knives from time to time. When a knife arrives in rough shape I can’t resist the temptation to ask the customer “What on earth happened to this knife.” There are a wide variety of answers and most customers are usually a little embarrassed to admit what happened. A couple of the more common and comical uses for knives are using them as replacements for a can opener or a screwdriver. There are also those who use their knife to separate frozen hamburger patties or cut into a frozen chicken. Using the wrong type of cutting board is another common culprit. Some customers won’t give any thought to using a cutting board made from glass, marble or granite and they wonder why their knife won’t hold an edge. These materials will flatten the edge of your knife in a heartbeat. The best alternative is a wooden cutting board. There is nothing kinder to the cutting edge of your knife and research shows that when cleaned with warm soapy water and dried, bacteria are not an issue. Second best would be a plastic cutting board but only a plastic board where a knife will leave a visible groove. A plastic cutting board that doesn’t show any marks is too hard on the knife edge. You might not think so, but some home knife sharpening machines can do more harm than good. I’m referring to the machines where you pull the knife through the little motorized grinding wheels. For knives with a bolster, these machines will only allow you to sharpen the edge up to within about a half an inch from the bolster. As a result, after repeated sharpening the blade creeps up and bolster hangs down below the edge and the back half of the knife can’t contact the board and cut through anything. The other problem that can develop with these machines is uneven sharpening. This deforms the curve of the edge that allows the knife to rock properly on the cutting surface. Believe it or not you can damage a knife by using too much force when steeling. The feathered edge is microscopic so it doesn’t take much persuasion to coax it back into line. When too much force is applied it can roll the edge over past center. When this happens repeatedly the metal at the edge will fatigue, break off in small bits and turn a smooth cutting edge into more of a saw with uneven teeth. Finally, if you ever got your knife back from sharpening and noticed that it seemed smaller and the sides were all scratched up your knife was probably the victim of a belt grinder. There are professional knife sharpeners out there that use this technique and they remove way more material from your knife than is necessary for sharpening plus the heat generated right at the edge may get high enough to weaken the temper of its steel.