Regardless of the quality of the cutlery when purchased, a knife is no better than its sharpness.  The factory edge on a knife represents less than one percent of that knife's life.  A knife gets dull when the edge, which is thinner than a human hair, folds over (see illustration).

     The secret to keeping knives sharp longer is to create an edge that resists folding as long as possible.  Chef'sChoice^® knives' edges are arch-shaped rather than "V"-shaped or hollow-ground.  An arch-shaped edge is symmetrical with more metal to support the fine cutting edge.  Typical hollow ground edges have less metal supporting them and thus readily fold over in use.  It is important that the sharpening method provide a symmetrical edge.  An edge that leans to one side will not cut straight and is prone to folding.  Creating an arch-shaped edge requires multiple-stage sharpening and precision angle control. 

     There are basically two types of sharpeners:  those that "straighten" the edge frequently (such as honing steels) in an effort to keep it from folding over and dulling quickly; and those that create a new edge by reshaping it (such as stones and precision angle-guided diamond abrasive sharpeners).  Traditional stones provide no angle guides and require effort, skill, patience and time.  The straightened edge is still weak and will quickly fold again.  Eventually the edge breaks off or folds so tightly that it can't be straightened with a steel and must be re-sharpened by other means.  Conventional high-speed sharpening wheels or grinders can remove metal excessively and detemper (overheat) the edge so that it is weak and will fold over quickly when used.

A Note on Detempering
     In one of the final steps of manufacturing, a knife is heated to precise temperatures, for prescribed periods of time in a process called "tempering."  Tempering strengthens the alloy by altering its structure.  If the knife is subsequently heated to a temperature above the temperature at which it was tempered, the alloy may become weaker and will not take or hold a good edge.  If sparks are produced during sharpening, the edge is extremely hot and it clearly is being detempered.  Sparks are actually bits of molten metal - evidence that the alloy along the edge is literally being melted by the sharpener.  Final "tempering" is done at very low temperatures such as 300ºF - not much above the temperature of boiling water.   To avoid detempering it is critical not to exceed that temperature at the edge itself during sharpening.  Sparks mean temperature is exceeding 1800ºF!!!

     Diamonds are nature's hardest known material.  They are uniquely suited to sharpening because they reshape an edge by efficient (cool) machining (somewhat like peeling off the skin of a fruit or vegetable) rather than inefficient abrading.   Conventional electric (and manual) grinding stones are made of mineral composites.   They remove metal by relatively inefficient abrasion.  Such abrasion produces excessive friction which can heat the edge hundreds of degrees or more and consequently detemper knives.  Most commercial grinders are no exception.

     The Chef'sChoice^® 120 Electric Sharpener creates a tri-beveled edge which gets sharper and stays sharper longer in a  three stage sharpening system.  The system consists of presharpening, honing, and stropping/polishing.  In the first two stages, conical disks coated with diamonds form two beveled layers and in the third, your knife is polished to a better than razor sharp edge using a special patented composite polymer material.  Stage one may be used for excessively dull or damaged knives or for maximum edge "bite"; stage two for routine sharpening and the final stage for polishing.  The whole time, the Chef'sChoice^® 120 customizes the hold and angle on your knife using high precision elastomeric angle guides, eliminating any guesswork on your part.  It is totally safe for all quality stainless, carbon and alloy steel knives with straight edge and serrated blades.  It has a fast and rugged 125 watt motor.  Comes with a three year warranty.   Made in the USA.