You have to sharpen a new knife a few times to get it cutting well. Right? Or do you? Are knife manufacturers improperly sharpening their knives?
knifesteelnerds.com
Thanks for posting that article because its a textbook example of how and why "links" and articles should at best be read with a degree of skepticism because even though the abstract points in the article are generally somewhat correct, the author and to a degree the "expert source" regarding sharpening either don't know themselves or are promoting an agenda and product at the expense of accuracy.
As a baseline for data;
ALL machining generates heat and stress ( and often magnetism) in the work- knives are no different.
On the "roughing" side, whether its a laser cut with a HAZ (Heat Affected Zone), a mill ( metal fatigue from the cutter teeth) or a profile grinder ( heat) all form metal and induce factors into the part- its an unavoidable part of the physics of part making.
That's what heat/cold treatment is for ( peening etc.) which normalizes all those things and makes them whatever the design is.
Heat treating ALWAYS induces a degree of deformation and dimension change in every metal part and with things like edges there is post treatment finishing when needed because of that distortion ( grinding/polishing)- again normal, expected and routine ( and easily dealt with)
Those grinding/polishing operations almost universally are on precision machines with balanced wheels with precision angles taking cuts with MICRON sized depths per pass and they wither have FLOODED or high pressure INJECTED coolant. That means a cold part and no sparks and thus no metal change other than a microscopic amount of negligible work hardening. There are often thermal imagers looking for heat.
The article doesn't directly draw the distinction with a difference between a correctly designed manufacturing process and a hand held manual "eyeball" thing. ( and this is not to say small manufacturers don't use modern or even proper methods but they are not the accepted standard)
But notice the article uses "hand grinding" as the example but doesn't say if it was "free hand" or in a precision jig with coolant nor does it give either a pressure ( how hard the stone is against the work) or the speed of the feed or the depth of the grind.
It leave the reader with a false impression on grinding based on a series of comments LACKING ALL NECESSARY INFORMATION required to justify the comments in the first place. ( ask any machinist about what effect speeds, feeds, jigs have to do with finished produce and induced stresses)
Then the author talks about edge retention and all kinds of stuff.
The term "edge" is a descriptive term for a FUNCTION. The "edge" is an ANGLE (geometry) so you don't "sharpen an edge"- you recut an angle.
That's pointed out because "sharpness" is a marketing term and snake oil reference that cannot be defined in any measurable way as a constant- an angle can.
The author buries that point like a "mystery" as to why a "ground blade" which may be ""duller" on that "cut scale" has a higher rating. The answer is simple and known throughout industry.
Grinding ( when done properly) is a precision operation resulting in a precision angle (primary and secondary)- a belt is whatever you wind up with even changing overall angles and moving off center of the centerline. ( that's why one may get a "sharp" edge but it doesn't wear well or last long)
The author talks about drawing the blade for "sharpness values" ( whatever that is) but without an optical comparator, precision metrology equipment (GD&T) and even a profilometer to run the edge- you are just using a Rube Goldberg device to get a worthless value.
Even with a good edge, if the edge is not centered to the run datum and tapered to the run with proper surface profile ( offset or angles changed and maybe dips along the run of the angle or taper) then the edge life is going to be very short lived and will dull or break easily.
The authors attempt to put some "technobabble" in the end of the article to appear to sound "sciency" or give credibility is pretty useless because the end user in most cases doesn't have the awareness to ask such questions or the knowledge of what it means if he did know. All he wants to do is "go ginsu" on an overripe tomato.
The summary is misleading and should be specifically changed similar to... ( for accuracy)
Knife edges are easily overheated during powered grinding due to the small volume of the edge and the friction buildup from grinding.
Knife edges are easily overheated during powered grinding when done by a human hand and eye because proper grinding requires training and subject matter knowledge, correct balanced trued wheels, proper stone for the metal, proper rigid jig, and depending on feeds/speeds and grind depth- coolant as well to produce a quality finished edge.
This softens the edge and worsens edge retention.
Excessive grinding load combined with improper techniques affects the blade metallurgy/geometry in random ways resulting in an improperly angled or otherwise damaged edge which will have a very short service life. ( If you are grinding with a heat build up that softens hardened steel- you have worse problems)
The use of steels capable of high temperature tempering treatments help to some extent since they can withstand more heat.
This is ridiculous on its face. What exactly does it help and what extent does it?
Hand sharpening or water cooled sharpening are the best methods for preventing overheating of edges.
Hand sharpening ( without all the aforementioned criteria) is the
FASTEST method to
ENSURE overheating and improper angles for edges.
Again, this is why links and articles are at best read with a critical discerning eye and by themselves "prove" little to nothing and are often simply wrong. ( obviously not all but just because somethings written doesn't make it true, correct or directly applicable in a given situation)
