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How to Sharpen a Knife with a Grinder

Knives can wear over time and can soon lose their sharpness. If you want to have a razor sharp knife for your desired purpose, you are going to want to consider sharpening your knife blade using a grinder.

This article talks you through the steps that you can use to sharpen a knife effectively using a grinder.

knife and log of wood


What types of grinders can you use to sharpen knives?

Perhaps the two best types of grinder to sharpen a knife are belt grinders and disk grinders. The beauty of these machines is that they can sharpen a knife quickly in comparison to using a steel. You can also vary the angle of the grinder to sharpen to your required needs.

They're also much easier to use than a sharpening stone and can produce a consistent and most importantly sharp end result. These grinders also have the necessary power to work with steel as opposed to wood.

You can use bench grinders also to sharpen knives but they are highly powerful and can often remove a lot of steel very quickly. A tiny knick at the wrong angle can permanently ruin the edge or appearance of the blade. Just small errors in judgement can result in the need for extensive re-grinding, taking you a lot longer and wasting more energy and money.

It's best to take a lot of time and care over your blade, particularly if you have built and designed the blade yourself in the first place.

Further reading: A step by step guide to making a knife


Selecting the right grit

Choosing the right grit is an essential part of the process. 100 grit is probably the best grit to sharpen a knife. However, if you have a tougher material such as high carbon steel, you might want to consider a 50 grit.

The blade can also require different types of grit for different purposes. A hunting knife or similar requires a lower number grit to ensure a sharper finish. However, some blades have more defined areas that require a number of different grits.

hand holding knife outside


Step by step guide to sharpening a knife with a grinder

The first part of the process is to clean your knife. You can do this by using a gentle wire brush, gently polishing the knife with an oily rag to remove any rust or dirt.

You then need to assess how many sharp edges your knife has. Some knives have two sharp edges, whereas others have one sharp edge and one flat edge.

You should load your grinder with your desired grit belt or disk. If using a belt, make sure that it is not too tight or too loose. You should have some tension but also a bit of give. Too tight or too loose and you could easily ruin your blade.

Start running the grinder and at first gently apply pressure up and down the length of the belt or disk. Hold the blade with both hands, flipping the blade if the blade is double sided. Whilst you are honing your skills, you should probably have one hand on the hilt and one hand on the blades tip to exert maximum control.

To achieve your desired grind, you should be extremely careful with how far you go in terms of contact. Metal can quickly be removed but cannot be restored, so go light and gently!

Once you have achieved your desired sharpness, you should look to cool the blade. The process of grinding will have generated a lot of heat and so it is important to cool your steel in water. The water will cool it immediately and prevent the blade from damage.

Once you are satisfied with your work, you can also use a very fine sandpaper to carefully finish your work and create that extra smooth and sharp edge.

At this point you should test for sharpness. You can do this by holding a sheet of paper and resting the blade at the top edge. If the blade cuts the paper with relative ease, then your blade is sharp enough. Finally, wipe down your blade and store it in a dry place before your next use.


Considerations when you are sharpening a knife using a grinder

You should really try and hone your skills with a grinder if you are a novice. It is difficult to master control at first and you can inadvertently take too much metal off the surface of the blade, essentially ruining your blade. This will reduce the lifespan of your blades, so it's imperative that you practice on other material first, or something that you don't mind ruining.

You should ensure that the grinder surface is absolutely dust free to maintain a smooth finish. You should also not keep your knife on the surface of the grinder for too long as more abrasion can reduce the lifespan of the knife.

Move the blade naturally with the grinder. Follow the natural curve of the blade when sharpening the knife. You should choose a grinder that can regulate the speed of the grind, making control much easier. Finally, avoid raising the degree angle of the knife while sharpening as this can actually make the knife blunter.

knives sticking out of a tree



Sharpening a knife using a grinder is quite a difficult method to master, so it is worth carrying out a lot of tests. This will save you a lot of money in the long run, as you are going to ensure that your blades last a lot longer and even have a new lease of life. Maintaining your blade can mean that you can also make it as sharp as when it was first made.

Grinding can be done with a variety of tools including diamond stones and bench grinders but the best for steel and creating a razor sharp blade are the disk or belt grinder. Soul Ceramics has a range of belt and disk grinders available, perfectly suited to sharpening a knife. We have the necessary knowledge and experience to advise you on the best grinder for your needs.

Further Reading: What Is A Belt Grinder Used For?