How do you sharpen a knife?

Question

Just got done sharpening a few knives, and thought it could be useful to post a question about it here.

So lets say I have one of these guys.

With a coarse stone, a medium stone, and a fine stone.

• What is the proper way to sharpen a knife with a stone like this?
• Do I need any other tools?
• Do I need any protective equipment?
• Do I have to use some type of oil?
• Is it better to go fast, or slow?
• Is the procedure different with a knife that has never been sharpened before?
• Do I have to do anything different if the blade has rust on it?
• How do I know when the knife is sharp?

Answer 1

It is very hard to describe knife sharpening in text. I'd recommend searching out a few Youtube videos for tips on technique. That said, I'll add my 2 cents worth. Everyone has a different idea of the "correct" way to sharpen a knife; below is just how I was taught.

What is the proper way to sharpen a knife with a stone like this?

If the knife is already sharp and you're touching up, start with one of the fine stones. If not, start with the coarsest. Work your way from coarser to finer. Put some oil on the stone, put the edge of the knife on the stone at the angle you want (try to match the existing angle), then stroke the knife along the stone as if you're trying to remove a fine shaving of stone. Pull the knife as you do it to sharpen the entire edge.

Do I need any other tools?

No. A jig for keeping the sharpening angle can help, but most likely wouldn't be usable with a stone like this.

Do I need any protective equipment?

No, but be very wary of where your fingers are, and where the edge can go if you slip. Keep your fingers out of that area.

Do I have to use some type of oil?

Yes, to carry away the swarf, or metal particles. For cooking knives I use a vegetable oil. Yes, veggie oil can go rancid, but cooking knives are used and washed often enough that it's not an issue.

Is it better to go fast, or slow?

Slow. I like to take long strokes along the whole edge, concentrating on keeping my angle consistent. I use about a 20 degree angle on kitchen knives.

Is the procedure different with a knife that has never been sharpened before?

Only that you would probably start on a coarser stone.

Do I have to do anything different if the blade has rust on it?

Remove the rust first with fine sandpaper.

How do I know when the knife is sharp?

There are many ways to test. The old newspaper test, where you hold a piece of newsprint in one hand and cut it with the other is a good one. You can try shaving your arm hair until you run out :)

But really, watch some videos and just practice.

Answer 2

The way I have always sharpened my knives is to turn an old cup upside down and run the blade across the bottom of it first one side then the other. You will be surprised at how sharp it gets. I learned this from my granny. It's quick, easy and cheap.

The technique can be seen in this video. Turn an old coffee mug upside down and use the unglazed edge of the porcelain

Answer 3

Sharp tools and knives are a joy to work with and produce better results, faster, and more safely.

The best book on the subject is The Complete Guide to Sharpening. My library has a copy, so check there first.

With good practice, anyone can learn to sharpen well. But you'll need to be able to recognize a sharp edge, correct honing angles, and how long to hone at each step. Developing those skills with tools you're trying to work with is very frustrating. Consider paying someone to sharpen for you to give you something to compare to, and pick one tool or knife to learn on as you go.

I once took my kitchen knives to the grocery store, where the meat department will sharpen for free. They came back sharp but the edges were not straight. There was a wave that I had to grind away before I could sharpen again. Uggh.

Today I take my knives to a sharpening service. He's very good, and it's easy and quick.

Kitchen knives are generally difficult to sharpen because they have a changing-radius curve. Getting the right angle across that is hard. I'm going to write about woodworking tools because kitchen knives are a natural progression after woodworking tools.

If you want to learn to sharpen, probably the easiest blade type is a hand plane. The edge is straight and the iron is size gives you a lot of control. However, the large amount of material also requires more patience. A 1" chisel is the same idea but a bit faster. If you grind the tip on a 6" bench grinder, it will get a concave shape that makes it easier to feel if the blade is on the stone at the right angle. Go slowly so you don't burn the metal. A simple jig helps you get a consistent angle.

To hone blades on a stone without honing your skill, add tools and jigs. For a plane or chisel, there are simple honing gides that give you a consistent angle without too much work.

My friend has a Tormek and loves it. He says that after many years of struggling, he now has sharp tools. There are accessories for just about anything you might want to sharpen. If money is no object, and you're not interested in learning a new skill, this might be the way to go.

Once your knives are sharp, take care to keep them that way. Make sure the food is supported by a surface that is softer than the knife, like a bamboo cutting board. Use a honing steel to touch up the edge often. Avoid pushing a knife through food (like an axe) instead draw it back and forth (like a saw). Don't let the sharp edge bump in to other dishes when washing it. Protect it from rust by drying it quickly and oiling it if you won't use it for a while. Be careful about where you store sharp edges - knives don't belong in drawers.

Answer 4

I like Japanese water stones, which use water as a lubricant. Those look like oil stones, but I'd check with the manual that came with them to see what to use as a lubricant. I'm not familiar with oil stones, but the technique should be the same.

For a knife that has never been sharpened before, (not talking about a new knife here; a commercially-made knife will already be sharpened when you buy it), you'll need to grind an edge on it. That's a bit more involved, basically you need a coarser grit on a moving wheel. This shouldn't be necessary unless you're making knives or restoring a knife that is so dull and rusty it doesn't have an edge anymore.

I think the hardest part is to get the right angle in the first place. Maintaining it isn't so hard once you get used to it. Once you have some experience, you'll be able to tell by the sound and feel of the edge sliding across the stone.

If you place the knife at a shallower angle than the edge, and slowly tilt it to a steeper angle, you can see your oil or water squeeze out from under the edge and form a thin line along the edge just as you reach the correct angle.

Another trick is to run a Sharpie or other permanent marker along the edge. As you remove material, keep checking to see if you're removing all of the black from the edge. If there's still some marker along the "blade side" of the edge, your angle is too steep. If there's still some along the "air side" of the edge, your angle is too shallow.

I usually start with either my coarse or medium stone, depending on how dull the knife is to begin with. I do five strokes on each side, then four, then three, two, and one. If I started with the coarse stone, I move to the medium stone at this point and repeat the process. To see if it's sharp, I use my fingernail. I run my thumbnail perpendicular to the edge of the blade. If it catches, I know it's sharp enough to move on to my finest stone. If not, I do another ten strokes (switching sides between each stroke) on the medium stone and test again.

The fine stone I have is something insane like 20,000 grit. It feels very smooth, and all it really does is polish the edge. It's probably overkill for kitchen knives but it's great for razors and chisels.

Answer 5

I can tell you one thing. In my opinion - sharpening knives very easy to understand but hard to do.

The hardest part is to maintain proper angle when sharpening. Japanese knives like smaller angle, german knives like bigger angle and your hunting knive is even bigger angle.

You need to look for a sharpening system that takes care of angles for you. Here is 2 choices that were recommended to me by knife maker-hobbyist (I'm not affiliated with any of those)

This sharpener system supposed to work very well but I watched video and still wasn't sure I can maintain angle :)

After I got this set - I sharpen knives in no time and I never was able to do it before with just a stone. Angle is perfect. I bought simple set but I got yellow stone later. With yellow stone - it just makes it perfect. I use 17 degree for my Shun knive, I had to make new edge because I think factory is 16 degrees for those. And I use 20 degree for German knives

Answer 6

A few odds and ends...

Another good test for sharpness of a knife is to hold the edge straight up so you can look along it. With a light above you (a point source of light would be best), look for any reflected light from the edge. A dull knife will show a visible reflection. Only once my knife passes the reflection test do I bother to test cutting paper with it.

For coarse sharpening, I like diamond stones, in two different grits depending on how much sharpening must be done. These are nice because water is a good lubricant. Once I get past that point, I use a ceramic stone to touch up the edge. If the knife is close to being sharp, I'll skip the diamond stones completely.

Of course, always take care when sharpening a knife. Hold the edge in a way so you will not carelessly slice your hands while sharpening.