It's the number one question any decent knife maker gets. How do you get a knife so sharp? If the artisan is honest, they will say something like practice and patients. Dang! Why do we always hear that about stuff that’s really hard? Truthfully, it is kind of so for hand sharpening a knife, but don’t despair. If you’re the kind of person who only takes three licks to get to the center of a tootsie roll pop, someone makes a sharpening system that even the wise old owl can use. If you’re patient and don’t mind practicing to learn what I call, The Zen Of A Well Sharpened Blade there are a few things to know about a fine hand hone. If you’re not, there is still ‘need to know’ info to make cutting tools safe, predictable and durable to use.
Some people picture a blacksmith setting in front of a big round treadle stone, rhythmically stomping the treadle as sparks fly from a blade. Others may envision their Grandpa sitting with a big gray whet rock rubbing his pocketknife in little circles, first one side then the other. When I think about hand sharpening, images of an ancient Japanese sword smith I saw as a kid have always stuck with me. Him sitting legs crossed on a mat with a wooden bucket by one knee and a little ornate bottle of sake by the other. I can envision the artesian sitting for hours gently rocking his newly forged blade in little circular motions on stone. The only stops are to ritualistically drip water on to the stone. Dozens of hours later he is ready to test his blade. Usually by hacking through a tightly bound bundle of bamboo. Though there are some gruesome stories of using corpses or enemy captives as targets. But I digress. Before we get to the wooden bucket there are a couple of things to consider. The first thing you need to do is to decide how you define sharp.
One definition of sharp is what feels sharp. You know what I mean. Either a quick flick of the thumb across or short pull along the edge and a pronouncement, “Yep, that’s sharp!" That little tug you feel notifying that first aid may be required is produced by the drag of a course edge grind. If you are satisfied with this definition you can buy any number of quick sharpening systems that make a knife feel sharp and cut. Edge geometry and job requirements are all you really need to consider to use these systems effectively.
You’ll need another definition if you want that "Oh, Damn" edge that leaves people with cut thumbs and astonished looks. Yeah, I know you aren’t suppose to rub you thumb along a blade to test it. But most people do. I’ve been making knives for nearly 30 years and I do it. Besides, most folks don’t carry a magnifying glass or bamboo bundles around with them for testing sharp. Anyway, a well-sharpened knife doesn’t feel sharp. A truly sharp blade cuts before you feel it! That’s the other kind of sharp. If you have ever had a run-in with a new single or double-edged razor you know what I mean. So I suggest you use a magnifying glass to inspect your blades. Dull sections will look kind of like something white or dull silver on the very edge of the blade under a magnifying glass. You might be able to see it with the naked eye in the proper light. Of course, if you have a well-stocked first aid kit or a ready supply of enemy captives…feel free.
After we define sharp, understanding Edge Geometry is a main component needed to accomplish an effective tool. If you research the subject you'll find a lot of blade tech pundits promoting 16 degrees, 32 in the overall, as the perfect angel for ultimate sharpness. The best I can determine, this belief probably dates back as far as ancient Japanese sword smiths and knife makers. Personally I don't know what the perfect angle is. I do know that the angle should be Job Specific. Any angel between 25 and 35 degrees in the overall will feel very sharp indeed. The question is, will it get the job done repeatedly? So you’ll need to pick edge geometry to fit the job your tool will be doing.
Just by way of definition, if you can picture a 30-degree art or drafting triangle shrunk down small enough to fit on a pin…that’s what a cross section of the edge should look like from handle to tip. The actual angle between the sharpening surface and centerline between edge and backbone of the blade would be 15 degrees. I know, clear as mud right? Just lay your hand on something flat. Now keep your fingertips on the surface and lift your palm to what you think is 15 degrees. If your hand were a knife blade and you did that to both sides, that would be 30 degrees in the overall, 15 per side. Also, as I express these angles as absolutes they are not. They are intended as reference or starting points. I don’t have a series of jigs or little triangles I use to check the angle. It’s just experience. You will have to decide the proper angle even if you use a sharpening system that allows you to adjust the angles precisely.
So, which geometry for which job? Shallow angles, that is angles that are around 35 degrees or less in the overall, are really good for work preformed on soft materials. Jobs like cutting leather, capping (removing pelts from game), filleting fish, dicing carrots or processing small game. A shallow angle combined with a hollow ground blade or a blade with a thin cross section glides easily through the work. Since there is little chance of hitting hard materials like heavy bone, there is little chance of chipping or rolling the edge. Oh yeah, rolled edge…a bad thing for durability. A rolled or wire edge is just what it sounds like. The edge rolls over to form a microscopic J shape. Rolled or wire edge is the most common cause for loss/lack of performance in cutting tools with shallow hone angles. A chip or nick can be lived with since it only affects a single spot on the blade. A rolled edge affects performance over a large section.
Rolled or wire edge is tricky because if it is not badly rolled it will actually make a knife feel sharp. If you have ever had a knife that you thought was really sharp and got dull after a couple of cuts, it probably had a wire edge. Barbers have used the tendency toward rolling in shallow angle edges for centuries to provide clean, pain free shaves with straight razors. Straight razors are job specific tools that have edge profiles kind of like a really thin wood chisels. They’re usually flat or even convex on one side with an extremely shallow grind and hone angle on the other, as little as 5-10 degrees. These edges are prone to flexing and rolling under use. The familiar leather strop is not meant to sharpen a razor. It simply controls the rolled edge of the blade so it contacts the face in a predictable manner and removes microscopic burs left by honing. Cool huh? However, just like knives, if the edge becomes blunted or chipped the barber has to resort to the honing tools. By the way, if you go into your local barber’s shop, notice one of those old timed big gray two-sided sharpening stones and there are no super fine/hard oilstones around… I’d suggest asking him, “How do you think I’d look with a beard?"
As the edge is stood up toward steeper angles, angles that approach 45 degrees or so, they become more durable. It also requires more force or pressure to do the work. Blades with edges approaching 45 degrees won’t be real good for shaving. They will hack out a new tent peg to replace the one your kids left in the back yard. That done they will still cut up the sirloin for your world famous campfire stew. The advantage to steeper angles is if the job requires a durable edge and there is a risk of contact with hard materials the edge will last long enough to finish the job. Sporting knives for large game like deer or elk fits this job description.
I said earlier that edge angles less than 35 degrees tend to blunt and roll. I prefer to sharpen the edge to around a 35 to 40 degree angle, plus or minus 5 or 6 degrees depending on the job. Choose an angle to provide the right combination of cutting ease and durability. A little practice and patients adjusting these angles will get you the perfect edge for the job your tool needs to do. For large sporting knives that are likely to be subjected to heavy pressures and hard materials I tend to stand the blade edge up closer to 40 degrees. No, most cutting boards would not be considered a hard material. Your counter top probably is. For smaller sporting and kitchen knives that will not be used as often for heavy or ‘hard use’ applications like your marble counter top I tend toward the plus or minus 35-degree angle. For blades intended for filleting fish I might lay the edge down even more to 10 degrees or so per side.
Of course all of this is somewhat dependent on the quality of steel the blade is made from. The less durable the steel, the more important choice of hone angle becomes. Edge retention, durability and sharpenability (I know it’s not a real word, but that’s how it’s usually referred to.) are functions of chemical composition and heat treatment of the steel. But that is and has been a subject for many entire books! Many knife makers and collectors have mystified the subject to the point of a sorcerer’s alchemy. It’s just simple physics, just like sharpening knives is simple geometry. The more the edge is stood up the harder it becomes to damage. It may require more pressure to cut, but you can help compensate for lack of performance due to less than desirable blade materials. That’s why I express angles as plus or minus 5 or 6 degrees. There can be some variation in performance between identical knives from the same maker. Blade tech is science, but not a perfect science! So try adjusting the angle to fit the job and steel to get optimum performance.
Choose a system that meets your definition of sharp. Researching sharpening equipment you will find a lot of discussion about microns of finish. This is important, but more than a little confusing. Frankly, how many zeros the particle size of a diamond hone has, just makes my eyes glaze over. So, unless you’re a closet engineer just know that even the finest of the easily available synthetic sharpeners is not as fine as the finest easily available natural stone sharpeners. No matter the system chosen, to get the best results...you must be patient!
Diamond, ceramic, steel and other common rods and stones are fine for course sharpening, adjusting edge angle or the first definition of sharp. Otherwise, they should only be used on extremely damaged or dull knives. If you’ve had your favorite hunting knife out back doing your best Les Stroud, Survivorman impersonation and find you can’t cut the tape on the wife’s newest eBay acquisition, you may need to resort to a more aggressive hone. These sharpeners work because they create a microscopic saw edge. Fine oil stones create microscopic saw edges too, but they are much finer. It is like the difference between a handsaw for wood and hacksaw for metal. Even if they’re made from the same metal and same hardness, the few large course teeth of a handsaw will dull more quickly in hard materials. The many finer teeth of a hacksaw will continue to cut consistently longer because there are more teeth to share the work. The sharpening system you choose will produce the same result in the blade edge.
For that first, feels sharp and cuts definition there is no shortage of systems to make the work quick and painless. Dozens of companies make devices that hold the knife and/or hone at a fixed angle so you can bear down and get at it. They usually involve diamond, ceramics or some similar honing rod or slab. They remove a lot of material quickly and work well for the purpose. If you just want to quick sharpen a kitchen knife I highly recommend systems that have a couple of ceramic rods or steels fixed at shallow angles in a V-shape. They are usually stuck in one end of a piece of wood so you can keep your hand out of the way and just pull the knife through the center of the V. Just a few light strokes and those potatoes are in trouble.
If your definition of sharp is the second “Oh, Damn" version, use the finest/hardest OIL STONE you can buy as the finisher. Yes they are a little more expensive and yes it takes a lot more work to get a very fine edge, but they are worth it. After deciding on geometry and establishing the hone angle with a course hone, super fine stone hones and patients are the only way I know to get the second definition of sharp.
To sum up, diamond, ceramic, steel and other common rods and stones are best saved for inexpensive or severely damaged tools. They remove a lot of blade steel quickly. They will change the blade profile quicker. These devices are the reason your grandmother’s old butcher’s knife is now shaped more like a pairing knife. This type of hone is best left for down and dirty quick edges, not your $200 custom. To prolong the life of that high priced knife only use the hardest or finest quality oilstone you can find. A few light strokes on a stone and a good cleaning after each use will insure you can pass that expensive blade on to the next generation of enthusiast.
The Zen Of A Well Sharpened Blade is what I call the act of hand sharpening to that second definition of sharp. Whatever the system and once you’ve established the hone angle geometry, the trick to a great edge is to apply the same number of strokes per side, have a light touch, smooth stroke and oh yeah, did I mention…be patient!
I actually start my first stroke toward me pulling into the edge, which is with the cutting edge coming at me. Count 1-10 alternating strokes with the edge toward and then away. Be sure to follow the edge contour and maintain a constant angle. At the end I start over with the first stroke away from me counting 1-10 again. It almost becomes a kind of Zen like meditative exercise. At least that's what I tell myself to relieve the tedium. To test that you have not produced a rolled or wire edge, simply lay the edge on your thumbnail just like you did on the sharpening stone and this time drag it away from the edge of the blade. If the edge is rolled the microscopic hook shape will scrape a little curl off of your fingernail. Simple huh? But please, be careful. If you've done it right you are holding a very sharp tool.
Applying too much pressure is a common mistake. It doesn’t matter if it is a diamond rod or oilstone, too much pressure will result in a rolled edge. Let the hone do its' job. You should only apply a couple of pounds of force to the tool. If your hand is cramping, you’re working it too hard. Loosen your grip and reduce the pressure you’re applying. The edge should slip evenly over the hone. If you begin to feel it grab or grit as you drag it you are probably not maintaining a constant angle.
Feeling a gritting sensation is usually from standing the angle up past the establish angle. The sharp edge is digging into the stone. Of course diamond, ceramic and other similar hones will have a gritty feel because of their larger abrasive particle size. Dang, there’s that phrase again. Anyway, with a little experience you will get a feel for the difference. A grabbing sensation is from laying the edge down below the established angle. The point where the back of the honed edge and the grind of the blade meet is dragging causing the honed edge to be lifted up. It slips and then grabs as it re contacts the stone. These are both signs that a consistent angle is not being maintained. I can actually feel a hone angle that may only be 10 or 20 thousands of an inch wide by rocking it up and down on the stone. With practice, you will be able to as well.
There are several sharpening systems to help hold the blade at a fixed angle on oilstones. They work and can free you to concentrate on those pressure and profile parts of the process. I recommend them. Systems that allow you to select any angle are best. They’re especially good for novices until they develop a feel for pressure and angle accuracy. If you’re concerned about scratching the finish as you sharpen, they will help with that as well. I don’t use them because a truly sharp knife requires a lot of time and I sharpen a lot of knives. Most of these systems slow down the process. This induces a loss of patients in me and in return a tendency to a courser stone. For that second definition of sharp this is not good! So, I suggest practicing on those knives you’ve stuck in the back of the drawer because they now just burse tomatoes. Since you can’t make ‘um worse, they’re perfect for learning the Zen of a well-sharpened blade.
JD is a 50+ year old knife maker with 25+ years experience. His work can be seen at www.jdbknives.com. He has a couple of Degrees. JD has been married since 1976. He says, "I didn't think I'd be alive for thirty years, little on think somebody would choose to live with me that long!" JD's favorite quote is from Kafka's letters to his father, "I am prepared to prove at any moment that I am not the man that my education has conspired to make of me."
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