There is no “right” way to sharpen hand tools, but there are a lot of wrong ways. My own sharpening regimen has developed serendipitously, but it fulfills the essential requirements of a good sharpening routine:
- It is simple.
- It is fast.
- It is easily repeatable.
- It results in a keen edge.
I offer the following not as a tutorial on how you should sharpen, but as an example of the essential elements of a good sharpening routine. I’ve tried to keep my explanations very simple, but I’ve added some footnotes for anybody who really wants the nit-picky details.
Aside from my bench grinder, which I use only for repairing damaged edges, I have three pieces of sharpening equipment: a DMT coarse diamond stone, a soft Arkansas stone, and a strop. I’ve been using the diamond stone for about eight years now, and it still cuts quickly.(1) The strop is a piece of leather glued to a flat piece of hardwood and rubbed with honing compound.(2)
Let’s begin with this chisel, whose edge I chipped the last time I used it. Here is the edge as it came from the bench grinder. I ground it at about 25 degrees. Most of the time, I’m sharpening tools that are merely dull from use, but either way, I take the edge through three essential steps.(3)
Beginning on the coarse diamond stone lubricated with mineral spirits,(4) I rub the bevel side to side. Normally I use two hands, but I needed one of my hands to hold the camera.
The coarse stone has removed metal all the way to the edge. You can see where the stone was cutting at both the top and bottom of the bevel. Because the grinder leaves a hollow, it will take several more sharpenings before the entire bevel is flat.(5)
More important is the part you can’t see, but that my finger can feel. There is a substantial burr on the back of the edge.(6) This burr tells me that it’s time to move on to the next stage.(7)
I now move to a finer abrasive, this time a soft Arkansas stone, also lubricated with WD-40.(8) I rub the bevel on it side to side, just enough to remove the scratches left by the previous, coarser abrasive.
The burr is still there on the back, but the bevel is shinier now.
Now I flip the blade over and rub the back over the stone. This flips the burr over to the bevel side of the edge. Just a few circular strokes is all I need before moving on to the final stage.(9)
I now strop the bevel (only pull, never push!), taking perhaps 30-40 quick strokes. This flips the burr over again, and it also polishes the cutting edge.
Finally, I turn it over once more and strop the back. Usually this removes the burr entirely, leaving a very keen edge.(10) Sometimes with a really stubborn burr, I have to go back and forth between bevel and back a couple of times until the burr is completely gone and the edge is brightly polished.
There are as many ways to test the sharpness of an edge as there are ways to sharpen it.(11) I like to test on wood.
An edge that will easily pare the end-grain of soft pine and leave a smooth surface will cut other woods just fine.
This whole process doesn’t take long–two or three minutes from start to finish.(12) A bigger cutting edge, such as a hewing hatchet or a drawknife, might take a little longer, but not much.
- Diamond stones have a reputation for wearing out quickly. I have had one diamond stone, a cheap off-brand, wear out very quickly, but good ones do not. They do, however, lose their initial aggressiveness quickly. (It says so in the instructions that come with the stone, but who reads those?) Don’t be shocked when this happens. A diamond stone isn’t really dull until the nickel matrix holding the diamonds on the steel plate has worn off. It’s pretty obvious when it happens.
- I use the green honing compound from Lee Valley. You don’t need much. I still have most of the bar I bought eight years ago.
- I have Chris Schwarz to thank for the “coarse-medium-fine” phrase, though he applies it primarily to hand planes. It applies to a lot of processes in woodworking.
- Diamond stones can be used without lubrication, but I prefer some liquid. It prevents the swarf from building up under the surface being abraded, and I think the stone works more smoothly with lubrication. I prefer mineral spirits over water because it won’t rust the tool if I neglect to wipe it perfectly clean.
- Some woodworkers prefer to maintain a hollow grind on their edge tools, so they must grind more frequently. It may be helpful, but it’s not necessary. In an ideal world, an edge tool of mine would be ground only once in its lifetime–before it leaves the factory–and I wouldn’t need a grinder. But the world is not ideal, and edges get chipped or otherwise damaged. Therefore, I own a grinder.
- Some people call this a “wire edge,” while others call it a “feather edge,” even though we’re all talking about the same “burr.” If you hate nomenclature that is confusing, please choose a hobby other than woodworking.
- This applies only to single-beveled tools, such as chisels, gouges, and plane irons. Double-beveled tools are sharpened on the coarse abrasive on both sides alternately until a burr develops. I then proceed as follows.
- I’ve tried several lubricants on my natural Arkansas stones, and WD-40 works fairly well. It’s cheap, widely available, and easy to apply.
- Some tools, such as carving gouges, require a more polished edge, so usually I insert a second “Medium” step here: a hard Arkansas stone, also lubricated with mineral spirits. I hone the concave backs of carving gouges with a black Arkansas slip stone, which takes the place of a strop.
- Sometimes, if you watch closely, the burr will detach all in one piece, and suddenly you’ll see what looks like a bit of extremely fine wire laying on the strop. Do let the strop remove the burr. Never break it off with your fingers, or it will leave a jagged edge that won’t cut as well as it should.
- Thanks to the Internet, the “arm hair test” has now become the ultimate test of sharpness–if your edge tool can pop hairs off the back of your hand or arm, it’s sharp. That may well be true, but it doesn’t tell me what I really want to know: will it cut wood? Besides, by the time I’ve sharpened a few chisels, usually the back of my hand is a bit sweaty, not to mention gummed up with sawdust, so the arm hair test is usually impractical for me.
- When I was first learning to sharpen, I took longer, but once I established an effective routine, I sped up a lot. If your standard sharpening routine takes more than five minutes per edge on the average, then you probably need to simplify somewhere.