Knife Sharpness, Sharpening Methods and Tools
By Gary Zinn
Tri-Hone knife sharpener. Illustration courtesy of Best Sharpening Stones.
How sharp should a knife be, that is the question. A bad parody of the opening line of the Hamlet soliloquy, perhaps, but a real question that garners a lot of attention among knife users.
In particular, there are many YouTube videos and Internet forums that focus on knife sharpness and sharpening. Topics range from which sharpening tools, techniques and gimmicks are best (in some sense) to whether knife A is better that knife B because the former allegedly can be sharpened to a keener edge than the latter. Then, there are the endless debates over which blade steels are hard to sharpen and which ones best retain their edge.
In my opinion, most of the contention over these topics is much ado about nothing. (No more Shakespeare references, I promise.) A knife should be sharp enough to efficiently and safely do the job at hand. Sharpening tools and techniques should be those that get adequate and consistent results for the person doing the sharpening.
Some popular blade steels are, to some degree, more difficult to sharpen than are others, but none are impossible. Some steels may take a slightly keener edge than others, or may be inherently more wear resistant (i.e., retain their edge better). These are natural facts and I do not understand why we get so wrought-up about them.
Degrees of knife sharpness
I have a qualitative ranking system for describing the sharpness of knives:
Here is a simple method I use to evaluate the sharpness of a knife and what I mean by these degrees of sharpness. I use a magazine or catalog with pages of thin coated paper. I pick up a page or two, punch the tip of the blade through the paper just below where I am holding it by the outside edge, and slice downward through the page(s). If the paper does not cut cleanly, then the knife is Not Sharp. If the cut is clean, but with noticeable resistance, then the blade is Sharp Enough. A clean, easy cut with little resistance indicates a Very Sharp blade, and if the knife zips through the paper with virtually no resistance it is Extremely Sharp.
This is a quick and consistent method of evaluating blade sharpness. In absence of a magazine or catalog, I can check a knife by lightly touching the ball of my thumb to the edge. Doing this, I can quickly tell if a blade is NS, but I cannot as clearly distinguish between SE, VS and ES as I can with the paper slicing test.
I do not shave body hair or do similar stunts to test or show off sharpness. I have seen people cut themselves doing such things.
NS means that some sharpening work is needed before the knife can be efficiently and safely used. SE means that the edge is acceptable for doing normal cutting tasks. When I sharpen a knife, I generally aim to get it to VS condition; then it will easily cut almost anything that should be cut with a knife and I will likely be able to use it for quite awhile before a touch-up is needed.
Extremely Sharp is my term for a knife that most people would call razor sharp or shaving sharp. I do not use these terms, because we are talking about knives, not razors. I do not normally sharpen knives to ES condition, mainly because it is extra work to get an edge to this keenness and it will usually dull back to VS condition very quickly. I will occasionally hone a special purpose blade, such as a Wharncliffe, to ES if I need to use it for fine work (e.g., cutting stencils or such).
In summary, my opinion is that generally a knife should be sharpened to VS condition. Then, whenever the edge falls back to SE condition, it should be touched up at the first opportunity. This makes for a much easier sharpening job than if one lets a knife dull to NS condition before resharpening.
Sharpening methods and tools
Sharpening methods and the tools suitable for each can be confusing. To sort things out, I divide sharpening methods into the following categories:
The first sharpening method listed is my way of doing the job. As I recounted in Knife Sharpening 101 - The EZ Method, I learned freehand sharpening at a young age and have refined my tools and techniques over the years. This method uses bench stones or a three stone unit, usually called a tri-hone, to cut and smooth a ground bevel on a knife.
Recently I invested in a Work Sharp Guided Sharpening System. This tool features two interchangeable diamond sharpening plates (320 and 600 grit) and a ceramic sharpening/honing module. An upgrade kit contains two additional diamond sharpening plates (220 and 800 grit) and a leather faced stropping plate.
This is a guided sharpening tool only in the sense that it includes a pair of wedges, mounted on the ends of the sharpener frame, to index the angle at which a blade is held before beginning to stroke it across the sharpening plate. It is not a guided sharpening tool in the same sense as those that use clamps and jigs to control the angle at which a blade is being sharpened.
Although I had used diamond sharpening plates a few times and had found them effective, I had not bought a set of diamond sharpeners, because I felt they were too expensive. The Work Sharp system breaks the price barrier, which encouraged me to take the plunge.
I still use my tri-hone (with silicon carbide, soft Arkansas and hard Arkansas stones) to sharpen "ordinary" steels, but I switch to the diamond plate tool when attacking high performance steels, such as ATS-34, D2 and S30V. Diamond sharpening stones or plates are quite effective on such steels.
For honing, I use the Lansky Master's Edge Sharpening System, a crock stick type sharpener, followed with a few strokes on a butchers steel. (See Knife Honing with Crock Sticks and a Butchers Steel.) Stropping is an alternative method for final honing of a blade.
Manual sharpening systems using guided sharpening tools (clamps, jigs and sharpening stones or plates mounted on guide rods) are quite popular. I have had enough experience with them to understand why. They yield quite precise and consistent bevel edges and can do everything from heavy grinding to fine polishing with the appropriate stones.
I do not prefer this system over freehand sharpening, because I find it to be slow and it takes some fussing to get the setup right for each blade being sharpened. However, I will not argue with anyone who likes this sharpening method.
For those who do, reasonably priced guided sharpening kits such as those made by DMT, GATCO and Lansky (image below) are widely available. Professional grade guided sharpening kits are offered by Edge Pro, KME, and Wicked Edge, but these are much more expensive.
Lansky guided sharpener. Illustration courtesy of Lanky Sharpeners.
I will dispense with manual and powered pull through sharpeners very quickly. I have tried several of these at one time or another and I distrust them all. My experience is that they get poor results and can damage blades, if not used very carefully. I do not use or recommend them and will not discuss them further.
Finally, power belt and wheel sharpeners merit mention. Most of these are professional grade machines and thus are unreasonably expensive for personal use. For instance, the Tormek T8 wheel machine costs almost $900 with a set of clamps, jigs and guides included for precise sharpening of knives. This is a heavy investment for a home use sharpening tool.
However, there is at least one power knife sharpening tool that is more reasonably priced for personal use. Knife designer Ken Onion has teamed with Work Sharp Tools to develop the Work Sharp Ken Onion Edition Knife Sharpener. This is a power sharpener that uses easily interchanged abrasive belts to sharpen knives, scissors and other edged tools. Besides easy belt interchange (five different grits), key features include a dial adjustable sharpening guide (15 to 30 degrees) and variable speed (1200 to 2800 SFM). Replacement belts and blade and tool grinding guide attachments are also available.
Each of the sharpening techniques I have listed has capabilities (advantages) and limitations (disadvantages). In addition, particular brands or designs of tools within each technique category may be better than others.
The stage is, therefore, set for the discussion and sometimes heated disagreement that I mentioned at the top of the article. Anyone thinking of trying a particular sharpening technique or buying particular tools should do enough research to understand the capabilities/advantages and limitations/disadvantages of the technique or tools in question.
In this age of the Internet video, I imagine that the majority of people wanting to learn about knife sharpening tools or techniques end up browsing YouTube. Internet videos are both a boon and a curse. A well done video that features factual information about the tool or technique in question can be quite enlightening, while a video that asserts, "this is the only good tool/technique for sharpening a knife" should be viewed with skepticism. Ultimately, videos can be sorted into the good, the bad and the ugly.
Videos produced by or on behalf of sharpening tool makers or marketers are mostly good, for much can be learned about the capabilities of the tool and how to use it properly. However, the viewer should assume that the video will stress the positive features of the tool and largely ignore its limitations. For instance, pull through sharpeners cut only one bevel angle on the blade, so anyone using these who needs a different bevel angle on some of their knives is out of luck. (This is only one of the reasons that I do not like pull through sharpeners.) In addition, product promotion videos will gloss over the fact that some sharpening tools (usually the more expensive ones) may require complicated adjustments to properly set up blade guides or jigs.
As a final example, the popular manual guided sharpening tools have limited reach, due to the length of the guide rods. Sharpening long knives on these tools becomes complicated, because one must sharpen the blade in two or more sections, due to the reach limits of the tool.
The best sharpening videos are those by experienced individuals who have no axe to grind (pun intended). These are folks who are trying to share objective, practical knowledge, rather than promoting a particular tool or technique.
Unfortunately, such videos are in the minority on the YouTube play list. Finding these objective videos can be a blind treasure hunt, but they do exist. One just has to develop a knack for distinguishing between the real thing and what is essentially promotional hype.
This said, I recommend a particular website that contains both a series of short videos on various sharpening topics, plus an excellent article on the basics of sharpening. These are on the A.G. Russell Knives website.
A.G. Russell started his long career in the cutlery business sourcing and marketing Arkansas sharpening stones. He has likely seen and tried every sharpening tool and technique devised within the last century, so he knows what does and does not work. He has made roughly an hours worth of video on sharpening techniques and tools, broken into fourteen short clips, each with a particular focus.
Russell has also written an article titled "How to Sharpen Using Stones," which can be invoked from the same web page where the videos are listed. Together, these resources are a trove of basic sharpening information. The direct link to the relevant web page is https://agrussell.com/KnifeSharpening .
Mr. Russell has his preferences and biases, like anyone else. For instance, he is very high on using ceramic rod sharpeners (crock sticks) for the final step in sharpening knives and for touchup sharpening. (So am I.)
He is not above subtly promoting some of the sharpening products he sells, but his videos and article are long on objective information and short on product promotion, so they are very useful. I recommend reading the article, even if one is not interested in sharpening on bench stones, per se. It contains a wealth of information on the basics of knife sharpening, whatever particular tools and techniques one might favor.
I do not totally agree with everything that Mr. Russell says or demonstrates, but our differences are mostly on minor points. My most notable criticism is that he sells tungsten carbide manual pull through sharpeners (I think of them as manglers) on his marketing website. I do not like these things, period.
Bad sharpening videos are sometimes the product of poor scripting or videography, but more often they are made by people who do not really know what they are doing. I believe those who post such stuff are more interested in playing with their video equipment and appearing on YouTube than they are in sharing their sparse knowledge. Examples abound, but one that sticks with me was a video that claimed to show how to sharpen a machete on a tri-hone sharpener.
The video ran for some ten minutes, with a young guy waving a machete around above the sharpener and expounding on how he would go about sharpening it. He never actually touched the blade to the tool.
Moreover, it was obvious he had never sharpened the machete at all. It was one of the low cost models that comes with a baked powder coating on the blade, including the factory ground bevel. These must be sharpened to a true cutting edge before they are usable, which of course takes the coating off of the bevel. The dude had not done this and I would bet that he had never used the tri-hone, either. I believe that both were fresh out of the box and he could not wait to show off his new toys. It was pathetic, really.
Perhaps even worse are those who hold that there is only one way to sharpen a knife, and that any alternative method is somehow incorrect or inferior. Here is an example I stumbled across recently.
Someone started a thread on an Internet forum, stating that he owned a specific brand and model of knife with a particular premium steel blade. He said he was having trouble getting a good edge on the blade (whatever he meant by that) and asked for advise. Needless to say, he got so much conflicting advise that he surely ended up more confused than he started. (Internet forums are notorious for generating confusion, conflict and outright bad information, whatever the subject.)
The most ridiculous response he got was from someone who asserted that the only way to get a good edge on a blade made from the specified steel was to hone it on an 8000 grit glass lapping stone. (The stone in question sells for over $100, I looked it up.)
I have news for the lapping stone freak. The manufacturer of the knife in question specifies that the blade is tempered to Rc 58-60. I have never sharpened that particular steel, but I am confident that I could, without undue strain, bring that blade to VS or ES condition using my diamond sharpening plate tool, crock sticks and butchers steel.
I say this, because Rc 58-60 is what it is. I have a number of knives tempered to that stated level and have not had any trouble sharpening them with the tools I mentioned. Sure, some steels are more wear resistant than others and a wear resistant steel may take more time and effort to sharpen than a more malleable one. However, if they are in the same Rc range they can both be sharpened using the same tools and techniques.
The ugly sharpening videos are those that show knives being sharpened with tools unsuited to the task. If you open a video and see a high speed bench grinder or belt sander being used to sharpen a knife, close it immediately and move on. Knives should NEVER be mistreated in this way.
A high speed grinder or sander will mess up a blade by changing the bevel angle, making the bevel uneven, nicking or gouging the edge, or overheating the blade enough to change the temper. Any of these disasters can happen in seconds on high speed power tools. Additionally, anyone who sharpens a knife on a high speed tool is running a high risk of personal injury if the blade slips or catches.
Finally, there are examples of bizarre sharpening techniques. Disregard any sharpening trick that seems weird. One that I saw recently involved a power drill, sandpaper, a hex bolt and nuts, and a hot glue gun.
The creator of this knife sharpening nightmare cut a strip of sandpaper and wrapped it around the chuck of his drill, securing it with hot glue. He turned on the drill and sharpened a knife on the rotating chuck. Next, he ran the hex nuts down on the bolt some distance, snugged them together and hot glued them in place. He chucked the bolt into his drill, fired it up again and ran the edge of the blade back and forth in the notch between the hex nut shoulders, presumably to hone the edge. I am not making this up, and I got chills writing a description of this farce.
Knife sharpening is not a black art. My father, who was legally blind for most of his adult life, could sharpen knives with the best of them, using nothing more than a simple bench stone, lamp oil for a grinding medium and a leather strop for honing. He taught me how to sharpen my first pocket knife before I was seven years old.
Neither does a good home sharpening setup require a thousand dollars worth of the latest gee whiz equipment. Select a sharpening method that suits your needs and capabilities, carefully select whatever tools are best suited to your method, and learn and apply the basics of effective sharpening. Then, enjoy the satisfaction of owning and using sharp knives.
Copyright 2017 by Gary Zinn and/or chuckhawks.com. All rights reserved.