Can You Sharpen a Knife With Sandpaper?


Sandpapers are the subject of debate in the knife making world for a long time. In most cases, knife makers have a similar opinion on each side. However, some people question the sandpaper’s ability to properly sharpen a knife. So, in this article, you will found out whether you should or should not use sandpaper to sharpen your knife. If a had to answer this as short as possible, it would go something like this.

You can use sandpaper for sharpening various kinds of knives. In fact, the sandpaper will sharpen a knife very well. Note that 200-400 grit sandpaper is generally used for rough sharpening. For finishing work, 600-2000 grit is typically recommended.

Ok, now you know that it can be done, but what sandpaper is the best for sharpening knives? Can you sharpen a kitchen knife with sandpaper? Can a knife be too dull to sharpen?

Let’s find out.

What is the best grit sandpaper for sharpening knives?

Ok, we have already established a knife can be sharpened by using sandpaper, the follow-up question is-Which one?

Typically, 200-400 grit sandpaper is used for major fixes like sharpening a very dull knife whereas 800-2000 grit is used for finer sanding. The higher the grit number, the finer sanding. In most cases choosing a range of 400-2000 grit sandpapers is ideal for knife sharpening.  

Note that the ideal grit size depends on the type of knife and what will be used for. For example, a grit of 200 removes a lot more material than grinding on a piece of 2000. If you have an extremely dull knife that you want to remove nicks from, 200-400 grit may be ideal for trying to bring it back to the desired sharpness. From my experience, I mostly use 600-1200 grit sandpaper. I have a sharpening kit that consists of 4-6 grits of sandpapers ranging from 400-2500.

However, if I am working with a kitchen knife that must be razor-sharp, I use 2000 grit. 2000 grit sandpaper gives a blade that you can shave your hairs off with. If you are sharpening a straight razor, you may want to consider using higher grit sandpaper, like 4000 for instance. 2000-4000 grit is a great spot for normal home use, especially when combined with 1000.

Even though that range may not polish your edge, you will notice the edge have a much smoother look. This is also an ideal place to spend some time on the flat section to remove scratches and leave with an even surface. After that, you can progress higher if you want a mirror finish on a blade. 6000-12 000 grits are for polishing the edge. The metal removal is so small that it is enough to start mirroring your material.

Few notes on knife sharpening with sandpaper

When it comes to sharpening a knife either with sandpaper or something else, the technique may be more important than your tool. Note that technique may vary from person to person, but everyone achieves the same goal, metal removal. To sharpen the edge, you want to remove excess metal and making it finer so you can achieve that razor-sharp edge.

If you look at your knife under a microscope, you would notice that the edge is serrated (microscopic teeth on the edge). The ideal edge would be finely polished that those teeth are as tiny as possible. Keep in mind that the finer the edge, the better edge retention. The smaller teeth are the harder it is for them to get chipped.

Another factor that plays a crucial role in sharpening is the type and quality of your steel. Basically, the primary goal for a blade is to have enough hardness to retain an edge and soft enough to take abuse. Note that there comes a point where you have to trade hardness for strength and vice versa. So, before you start sharpening any knife, you should know what the knife is used for and what steel is made from.

Keep in mind that different blades have different grinds. Some of them are flat ground where the entire blade is the bevel. Others may be a hollow grind, meaning it is a concave grind near the edge. Each type of grind has its own properties which should be taken into account when sharpening.

One of the common sharpening mistakes is pushing on a blade. I would recommend using two hands so you can have much better control over the pressure on the edge as well as to maintain the ideal angle.

You will know you have created a sharp edge when you developed a wire edge down the length of the blade. You should get your nail stuck on it. To make a balanced edge I recommend counting strokes and use a descending scale. When you feel the wire edge on a portion of the blade, you want to transfer your focus on the other parts of the blade so you don’t remove too much material.

Once you established the edge, it is time for using higher grits. This is where the angle of sharpening becomes crucial. If you don’t maintain your angles during the sharpening, you could easily refine the belly of the blade instead of the edge. Usually softer knives go from 20-25 degrees while the harder ones from 12-20. However, 20 degrees angle is generally accepted as a standard angle.

Which abrasive grains are best for knife sharpening?

Choosing the right type of abrasives is a key part of the sharpening process whether you are rough sanding or doing the polishing work. We know that each of these steps requires different sandpaper grits, but the grain type is also very important. But what should you pick? With so many different abrasives in today’s market, it can be overwhelming to make the right decision. There are two types of abrasives, knifemakers typically use for the sharpening process: silicon carbide and aluminum oxide.

Let’s take a closer look at each.

Silicon Carbide Sandpaper

When compared to aluminium oxide, silicon carbide sandpaper is sharper and harder grain. However, it is not durable due to its brittleness. Because of its razor-sharp grains, silicon carbides don’t have problems cutting metal under light pressure. A general rule of thumb for sanding with this type of sandpaper is to start out with lower grit numbers and progress to higher ones to add a finer touch.

Silicon carbide sandpaper is commonly used for finishing work because it is extremely consistent in terms of cutting. This one is also more expensive but the level of consistency justifies that price. It is usually black in color.

Aluminum Oxide Sandpaper

Aluminium oxide is actually a chemical compound consisting of aluminium and oxygen which are fused together and then sorted by grit size through various mesh screens. It is the most versatile type of abrasive grains. Aluminium oxide is also used in various types of sanding, including belt sanding, hand sanding and power sanding.

It is also known for its exceeding durability. The combination of durability and low cost is what makes it stand out over other types of sandpaper, including silicon carbide. Aluminium oxide sandpaper is suitable for both wood and metal sanding. When it comes to hard metals, such as stainless steel and titanium, this type of abrasive doesn’t have as long a life. And as for other metals, the aluminium oxide sandpaper will do just fine.

Aluminium has a “blocky†grain structure which makes it more durable than silicon carbide. However, it typically does not remove metal as quickly as silicon carbide sandpaper.

So, which one is better for knife sharpening?

Generally speaking, silicon carbide sandpaper is better for removing large amounts of metal quickly. On the other hand, aluminium oxide sandpaper is a little less aggressive which can be used for polishing. Due to the lower price of silicon carbide, it is far more popular for knife sharpening.

Recommended sandpapers for knife sharpening:

Anezus 90Pieces Sandpaper 400 to 3000 5000 7000 Grit (affiliate link)

AUSTOR 102 Pcs Wet Dry Sandpaper 60 to 3000 Grit (affiliate link)

Conclusion

While it may not be effective as whetstones, sharpening various kinds of blades can be done by using hand sandpaper. Sandpapers are an easily available and cheap option for all knife users to sharpen their edges. Choosing the right grit size is crucial before you start sharpening it. Otherwise, you could completely mess up your blade. In terms of abrasive types, both silicon carbide and aluminium oxide sandpapers can be used, although silicon carbide type may be superior for knife sharpening purposes.

Recommended reading:

How Thick Should a Knife Blade Be? (Detailed Analysis)

How to Test Steel for Knifemaking? – 3 Simple Tests

Albert from Wyoming

Hi, Albert here... Forging World is the place where I share everything I've learned (and still learning) in my 20ish years of experience in forging. Hope you like the blog and #keepforging #keeplearning

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