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Here’s How to Sharpen a Knife with a Rock

Here’s How to Sharpen a Knife with a Rock

Some adventurers believe a blunt knife is less useful than no knife at all. I believe them too – if you are trying to survive with next to nothing, your knife will be your gateway to food, shelter and protection.

Even if you are lucky enough to have a sharp knife with you, surviving in the wilderness will mean your knife will be exposed to a lot of wear and tear, and it will become blunt over time.

Luckily, those great outdoorsmen have figured it all out and have devised ways to sharpen knives without any equipment or a traditional whetting stone. Here are some tips on how to sharpen you knife on a regular stone.

To sharpen a knife on a stone you need to find a fine grained, rounded stone, with a flat surface from a water source such as a stream. Wet the stone properly and start rubbing the edge of the blade on the flat side of the stone in a circular motion for about 30 cycles. Repeat the same amount of cycles on the other side of the knife, while periodically wetting the stone. Once sharp, polish the blade by stropping it against a leather belt or some strong material.

The type of rock you choose will affect how well it sharpens you knife. In the section below, I look at what rocks are good sharpening candidates, and where to find them. We also explore how to make a primitive knife in a worst-case scenario – where you are lost in the wild with not equipment at all.

What types of rock are best for sharpening a knife?

There are three important factors you need to look for in a rock before you can use it as a knife sharpener (Source: Bush Camping Tools).

  • The texture or grit of the rock. When you are considering sharpening your knife on a rock, you have to be careful not to use a rock that is too rough as this will simply scratch and damage you blade even further. Igneous rocks can contain crystals that make them too rough for knife sharpening.

A rock surface that is too smooth will also not sharpen your knife and will simply waste your time. Quartz is a good example of a rock with too fine texture. Your best choice is a rock that has the texture of sandpaper such as sandstone, which is a sedimentary rock.

  • The size of the rock. The rock should be large enough so you can move your knife over it in a circle that covers the whole blade. It should not be too large, as the weight would make it uncomfortable to hold and carry.

Also, the larger the stone the more likely it is to have an uneven surface, which is not what you want either. Opt for something intermediate that feels easy to handle.

  • The shape of the rock. You want the surface of the rock that you are going to use to be as level or flat as possible. You can try to flatten the rock a little by rubbing it against another rock of the same material, in order to flatten the surface even further.

Rocks from rivers or riverbeds are a good option because the water tends to flatten the stones over time, and you are thus more likely to find a good workable stone here.

If all else fails, you can also try a couple stones that seem closest to what you want and see which one works best. Once you find a stone that sharpens your knife properly, make sure to hang on to it incase you need to use is again. Cutting vegetation, hides and other tough material will eventually dull your knife again.

If you have the perfect sharpening rock with you, all you need to do is wet it with some water and you are set!

Why should you hone your knife after sharpening?

Sharpening a knife takes a small amount of metal off the knife’s edge, as it is literally scratched off by the grinding stone. This will sharpen the edge of the knife but will not ensure it stays sharp. A knife goes blunt because the edge of the knife, where the steel is very thin, gets bumped, nicked, misshaped and bent through use.

The nicks and bumps will be removed by the sharpening action but honing or stropping is needed to straighten the blade edge. A straight blade will stay sharper for longer, so honing a blade is an important part of maintaining a knife.

Sometimes just honing a knife can make a huge difference, and sharpening is not always needed. Some things that you can use to strop or hone a blade include:

How to make a primitive knife

A stone knife may seem like a very primitive tool, but if you were caught in the wilderness with no way of protecting yourself or building a shelter, any knife offers an advantage. Therefore, while you may not want to cook a gourmet meal with this one – it is great to know how to make a stone knife in an emergency (Source: Outdoor Life).

Fortunately, making a primitive stone knife is easy. Most parts of the world have rocks that will break with a good cutting edge. Stones that work well include flint, chert, jasper, chalcedony, quartz and obsidian.

There are two methods you can employ to create a piece of stone with a sharp cutting edge. The first method is more likely to produce a sharp flint, but is more difficult to use. This is known as bi-polar percussion.

The second is known as direct percussion and is much easier to use, but you may have to repeat the process several times to produce a well sharpened flint.

In both cases, you will need to hit your target rock with a hammer stone that should be 4-5 times larger than your target stone for bi-polar percussion or small and round for direct percussion. Wear protective gear if possible as the stones can splinter and cut.

  • Bi-polar percussion is a bit more complex, but more likely to splinter off a sharp stone blade. This involves placing the target stone on its longest axis on a large piece of rock that will serve as an anvil. If you strike it hard with your hammer rock on this axis, the shock waves may just splinter off a sharp rock blade that you can use.
  • Direct percussion involves flaking off sharp shards of your target stone by hitting its edge with your smaller round hammer stone. Your target rock should be flat and about the width and thickness of a sandwich. Once you found it, place it on the ground, not an ‘anvil’ stone, and strike it hard near the edge to chip off a blade.

Once you have your sharp stone blades, you should keep all the useable ones with you as replacements. These can be used just as is to cut or scrape food, to prepare twigs and sticks for building a shelter and even for hunting. If you have rope or wire with you, you can tie it to a small stick to use as a handle.

To conclude, maintaining your knife is the wild is possible and, in an emergency, you can even construct a knife from the sharp flakes of a stone. Who would have thought that rocks and stones could be so useful in the wild? Nature has truly thought of everything, if we are only creative enough to explore it.