Sharpening – a basic intro

It took me forever to learn to sharpen. I recently learned there are many who have yet to learn. I thought I’d share what I learned.

First a note. With the exception of electric high-speed grinders and little pull-throughs, every system I’ve seen works — PROVIDED you pay attention to what you’re doing. A lot of people think the system will do the work so they don’t have to — and can’t understand why they’re not getting “SHARP”.

I finally learned to get sharp when I really, really realized that sharp is the result of two planes intersecting. Once I realized I need to try and get every single pass of the blade on the sharpener to exactly the same angle, and figured out how to do so, it started working.

I actually use a few different techniques depending on what I’m sharpening. I’m not going to share them all simply to avoid confusion. Instead I’m going to use one that works consistently to make good (though not scary) sharp blades. I’ll add a couple of brief notes about other systems at the end.

You want your blade (I’m going to assume it’s a knife), a coarse stone, a fine stone, and a leather strop. Ideally you want stones three or more inches wide and at least as long as your knife, but you can work with smaller. Water is optional, oil is optional, rouge is optional. Oh, and while learning you want a black marker.

Set your coarse stone on a flat surface, making sure it won’t skid around while you’re using it. Take a moment and blacken the edge of the blade – both sides, about an eighth of an inch wide. Pick up your knife, and grip it for sharpening. That is, grip it with thumb on one side of the blade and fingers on the other so the blade faces away from your hand. If you can (if the blade is long enough) use both hands. Now when you sharpen you’ll be pushing the blade along the stone. When it’s time to reverse you’ll regrip the blade so the handle is on the other side. Remember I’m teaching someone who does not know how – after you “get it” you can develop shortcuts.

Now here’s what you need to do. Put the tip of the blade and the thumb closest to that tip on the coarse stone. You’re going to push the blade down the stone, gradually turning it so your other thumb comes into contact with the stone and then sliding as you push it. Your goal with the slide is to make sure you’ve brought the entire blade in contact with the stone by the time you reach the stone’s end (you’ve pushed as far as you can).

While pushing, you don’t need to press heavily downward. The weight of your hands is plenty for this.

When you’ve completed a push, lift the blade up so you can see where you marked the edge. If the mark is still there, go again. Repeat till the mark is gone (or it becomes obvious you made too wide a mark, in which case you’re aiming for a line of bright steel at the edge which is about 1/16 to 1/8 inches wide.)

Digression: I mentioned that oil and water are optional. What they’ll do is help your stone grind your blade more efficiently. See, when you make your run the stone grinds off metal shavings. As should be obvious, the metal shavings wind up on your stone, and will fill the tiny ‘gaps’ in your stone. This makes the ‘tooth’ of your stone less prominent which means it grinds less efficiently. Water and oil help float the shavings away from the tooth. If you’re not using water or oil (as your stone maker recommends), blow firmly across the stone between each push. End of digression.

You now have a bright and shiny edge on one side of the blade. Take a moment to make sure your stone is clean, pick up the blade the same way you did before but this time with the handle pointing the other way, and back to the pushes.

When you’re done here you’ve got a nice clean line on both sides from the coarse stone. You can, if you’re in a hurry, stop. There are two problems, though. First, the blade is ragged, and second you’ve got a burr which is going to interfere with cutting.

The ragged part of the blade is due to the coarseness of your grinding stone. If you look under a microscope you’d see huge gashes and a very ragged edge. If you were to use it in this ragged state it would seem to cut very well for a bit. Actually it’d tear as much as it cut. The jagged projections would catch on things and bend over or tear, however, and you’d rapidly end up with a duller blade.

So you’re going to repeat the process you used with the coarse stone, this time using the fine stone. Yep, marking, placing the hands, pushing till the lines gone, clean stone, reverse grip, push till the black line is gone. Now you’ve got a lot smoother surface – something closer to truly flat. You could do more, but that’s headed toward the other techniques, so not for now. As of right now you have two very smooth edges coming to a very sharp angle. But you still have a burr.

The burr is an inevitable result of sharpening. It’s a paper-thin (or thinner) bit of metal that’s gotten shoved in front of the edge — in profile it’d look almost like a spike. Well, a bent spike. See, it’s so thin it bends easily. With this bent spike in front of your edge you can’t cut anything – it’s like having the blade protected by a round sheath. So what you want to do to finish the blade is use a strop.

Your strop can be a lot of things, but I recommend a fairly heavy leather belt. What you’re going to do is use it to pull that burr off the blade. Note, not slice it off, PULL it off. Do not mark your blade this time. Use the same grip you used before, but start at the far end of the belt and pull it toward you. This time you want to press more heavily – don’t try to break off your fingers, but do try to press enough your fingers get a little bit of workout. Do this ten times, then reverse the grip and do it again.

Now as it happens you really didn’t need to use that grip for stropping. You could have done it gripping by the handle. Because of the resilience of the leather and what you’re trying to do it’s very forgiving of the angle. That is, you don’t have to hit EXACTLY the SAME ANGLE every time. However, it helps. Making you use the sharpening grip gets you into the proper mindset.

I also want to point out you can use rouge on the strop. It helps pull the burr off a bit faster. It also smooths the sharpened edge a bit more – and smoother is (for your point of use) sharper.

If you’ve been using your blade a bit and want to touch up the edge but not go through the whole sharpening thing, you have two choices: the strop or a steel. Believe it or not both are going to do pretty much the same thing. They’re going to take the very far edge which has gotten pushed around enough it’s almost a burr and push it back to being an edge. The strop will pull off that which is too small to stay firm while using, while the steel will push it back into alignment. Each is better in its own time. If you’re going to do it “right”, I recommend a stropping before you use the blade, steel-work during the job, and another stropping at the end of the use — after cleaning and just before putting it away, for example.

I said I’d give some extra information at the end. I want to talk briefly of angles, micro-beveling, and the scary-sharp technique.

I have seen a great deal written on the ‘best’ angle for a blade. I’ve come to decide that there’s a great deal of personal preference involved. However there are some certainties. The most important certainty and the one I’ll mention here is the trade-off. See, the narrow the angle of the cutting edge the more cleanly it will cut. At the same time, the narrower angle gets bent and banged more easily. In general, then, your tradeoff is cutting better or cutting longer. Adjust to the purpose of the tool. An axe is better with a wider angle, while a filet knife should have a very, very narrow angle.

Micro-beveling is a ‘trick’ with a couple of goals. First, it attempts to partially solve the thin-thick issue. Second, it tries to escape the vacuum-seal tendency of cut materials. What happens is that you sharpen as normal. Then you ‘cut off’ the very end of the angle with a wider angle – wider by a couple of degrees. If you’re doing it on a chisel microbeveling one surface is fine, while a knife or axe does better with a couple of degrees on each side to maintain the balance. The material starts sliding up the slightly wider microbevel, and then the metal ‘drops away’ under it breaking the bit of vacuum seal. Also since the very edge is just a tiny bit wider angle it’s a tiny bit more resistant to the wear of thin angles.

If you’re lazy, microbeveling also lets you cheat later sharpening for a bit. Just grind and polish a bit more microbevel and go back to work. Eventually you have to do it all, of course, but it does work.

Finally, I want to mention scary-sharp. I personally have had great success using it for flat blades – chisels, planes, that sort of thing. My success with blades with curves (most of my knives) is less dramatic.

Scary-sharp is an attempt to bypass the need for stones – and more important the need to lap (make completely flat) the stone. Lapping is only important in certain cases – where you need the cut to be perfectly flat and even. Again, chisels and planes. Anyway, what you do is glue various grits of sandpaper to a thickish piece of glass which you place on your flat surface. By various grits I mean start with maybe 200 or 300 and go down to 4000 (or finer). To make it work effectively your thumbs aren’t good enough — you’ll want a hard jig, whether it’s a wedge of wood or something fancier (and more expensive). (If it’s a wedge you need to make sure the wood doesn’t run on the sandpaper. Think about it.) What you will get from the scary-sharp is something that is, well, scary sharp. Again, I’ve never managed to make it work on a curved blade. (Well, curved beyond the very small belly a good plane blade has, anyway.)

I hope this has been of use, and hope even more that you learn to sharpen sooner than I did and do it better than me.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s