By accident I came upon this site:
Tech Edge by Furitechnics
It has a number of articles on knife edges that were pretty informative to me. Here's a sample article:
Knife edges under the microscope (or, Füritechnics de-mystifies knife edges)
There are a lot of funny ideas in Australia about knife sharpening, because few have spoken to knife engineers about the subject. Füritechnics is Australias only knife engineering company, and part of our mission is to de-mystify a lot of the 'wild knife stories' we hear constantly. Many of the fallacies really are very basic, and easy to explain in a metallurgical/physical sense!
Füritechnics designer, Mark Henry, analysing the cutting edges of knives with a Scanning Electron Microscope (SEM). Ongoing research includes the analysis of cutting edges of different knife materials, at different stages of wear, with different edge preparation techniques (including coarse and fine Steels). Some micrographs from Füritechnics SEM analysis are shown below.
This micrograph shows a Füri knife edge at 200x magnification. This edge has the standard factory grind, finished with 6 strokes on the oval diamond-coated Füri Steel. Note the sharp gouges produced by the diamond facets, which meet at the edge to form sharp 'saw teeth'. A standard smooth hard-chrome Steel will not produce such strong and sharp teeth.
The same edge at 2000x magnification: a closer look at the 'gouges' produced by the diamond facets. The steep sides of these gouges also act as cutting teeth (not all the cutting is done by the very edge). The gouges and ridges are stronger than the teeth on the very edge, and add to the retention (life) of a sharp edge.
This micrograph (200x) shows the cutting edge after the equivalent of 3000 cutting strokes on a PE cutting board (worn in the Füri wear simulation apparatus). Note the wear marks parallel to the cutting edge, and slight 'rounding' of the ridges.
A closer view of the wear marks (2000x): the wear can be seen on the tops of the ridges. This wear is quite localised, and is confined to the very tip of each ridge. The edge will take a lot more wear before the ridges are 'rounded' enough to seriously affect cutting performance.
As a result of our research, we have found that coarser-honed knife edges cut more efficiently because the small saw teeth increase cutting efficiency whenever a forward motion is used (the most common cutting action used by professionals, particularly with Cooks knives). CATRA (UK-based knife testing organisation) has also found that coarse-honed edges retain their sharpness for longer than fine-honed edges. The Füri knife material is uniquely suited to this coarse hone because it is tougher material than the more common CrMoV knives: the small saw-teeth dont break off as easily as the more brittle knife materials.
Because Füritechnics is a knife and kitchen tool engineering/design company, a very high level of expertise can be applied to finding new solutions to old problems. Such knowledge has led to the production of the revolutionary Füri knife range and Füri accessories.
The development of higher performance cook's tools is part of our mission. Producing those innovations to a very reasonable cost, and making them easily available to our customers, worldwide, is also crucial. Füritechnics is successfully achieving this mission, largely due to our design expertise. This design ability and focus is what makes Füritechnics so different to its competitors.
Some common knife sharpening fallacies include
A Steel does not sharpen a knife, it hones it
Well, I haven't yet met a person telling this story who can actually describe the physical difference between 'sharpening' and 'honing'! It seems to me that if a knife is 'blunt', then you Steel it until it becomes 'sharp', then you have just used a Steel to 'sharpen' the knife! This fallacy is partly driven by the old theory of 'sharpening' a knife on a stone (or grinding belt/wheel), then 'honing' it as fine as possible on a smooth Steel. Times change: it has been found that a fine-honed edge is not as efficient at most cutting operations (all cutting operations that involve a forward or backward motion of the blade, such as most cook's knife work) as a coarser- honed (sharpened) edge. A coarser-honed (sharpened) edge will also hold its edge for longer, particularly with a knife material that is tough (as described in the text above).
A Steel is used to 're-align the molecules' of the knife edge
Actually, molecules are much smaller than these story tellers think! A collection of atoms of various elements make the molecule of a compound, and one or more atoms of one element make a molecule of that element. A single scratch from a Steel may measure 1/100th of a millimetre across, and this may span thousands of molecules! A Steel simply makes scratches in the knife material which form many small cutting edges and 'teeth'.
A Steel 'straightens' the knife edge and 're-aligns' it
We think this is partly true, even if the story teller doesn't often understand why! It is true that Steels are useful for removing any 'burr' formed during grinding or 'stoning' a knife edge. However, once the knife has been used for some time, with or without a burr present, it is simply mechanical abrasion (with some interplay of corrosion) that erodes the sharp gouges and 'teeth' produced by the Steel (or stone, etc).
Some Steels are magnetised to 're-set' the polarity of a knife
Not all Steels are magnetised. If a knife has some magnetic polarity from using a magnetised Steel, it has absolutely no effect on the cutting of foods! This one should require no further explanation!
Hopefully the more 'scientific' and factual content here has helped dispel some of the myths you may have encountered!
