Do You Know What a ‘Round Edge’ Is?「

When it comes to knife sharpening, there are various techniques like Hamaguri edges, straight edges, and Itohiki edges. But one of the worst examples of poor sharpening is what we call the ‘round edge.’

A round edge is when the edge of the knife becomes rounded, hindering its ability to cut through food smoothly. Although the knife still has an edge and can cut, it requires a lot of force to actually make the cut.

Even if you try your best to avoid creating a round edge, there’s one main cause that can still result in this problem. Can you guess what it is?

The answer is the ‘warp of the whetstone.’ When you sharpen a knife with a warped or concave whetstone, the edge of the knife will follow the shape of the whetstone, leading to a rounded edge.

The more you sharpen with a warped whetstone, the more pronounced the round edge becomes! To prevent this, you can use a ‘diamond whetstone,’ which maintains a flat surface.

However, good quality diamond whetstones are quite expensive. Spending $200 or $300 on a whetstone might not be feasible for everyone. But for professionals in the knife sharpening business, a diamond whetstone is very handy.

Another way to avoid this issue is by consciously maintaining the flatness of your whetstone. Keeping the whetstone flat is common knowledge in knife sharpening, but it’s easy to forget. Maybe because the focus is usually on the knife itself?

‘Remember to flatten your whetstones, everyone!’

But just saying that doesn’t solve the problem, does it? (laughs)

What if your knife already has a round edge? How do you restore it to a straight edge? I’m planning a special feature on how to do just that. Please stay tuned!

• 2010-01-08