I just sharpened my first knife. It’s not as sharp as I hoped. What the deal?

I just sharpened my first knife. It’s not as sharp as I hoped. What the deal?

This is probably our most frequently asked question and, thankfully, the answer is usually very simple. The first thing to check is that your stones are making it all the way to the edge of the blade. The best way to check for this is to use a marker to color in the bevels and then rub the stones across the blade. If the stones are removing all of the marker, then you are getting very close to the edge. There is more on this subject, including diagrams that show how to use the marker here: How to Find Your Angle . The next step is to make sure you’ve created a burr down the entire length of the blade, first from one side and then the other. This step is crucial because it gives you definite proof that your bevels meet a point and that you have “apexed” the edge. If your bevels don’t meet, your knife will never be truly sharp. There is more on creating and detecting the burr in this article: Drawing a Burr. If you’ve successfully drawn a burr from both sides of the blade, you’re most of the way to having a sharp knife.

The next thing to consider is if you’ve chosen an angle that is acute enough to give you the results you’re seeking. If you have chosen a very wide angle, your knife will not be as sharp as it would with a more narrow angle.

The last thing to look at is the newness of your sharpener because your new diamond plates are not yet broken in. Your diamond plates require a number of sharpenings to knock off the loose diamonds before they start to really give you great results. You’ll find that the more you use them, the better your edges will get. New, out of the box, your diamond plates will produce fairly rough, ragged edges which won’t be very sharp when cutting paper or shaving hair; they’ll be great on tomatoes though. As your stones break in, your edges will get more and more refined. Edge refinement is important because it influences how your knife will cut in a given application. Every abrasive, like your diamond plates, makes scratches on the bevel of the knife. Ideally, those scratches extend all the way to the edge of the blade where they form micro-serrations. A very coarse stone will create deep, wide scratches that will form large, jagged teeth at the edge of the blade. A fine stone will create very small teeth. Depending on what you’re cutting and how you’re cutting, you may want bigger or smaller teeth. The general rule of thumb is that more aggressive teeth are best for cutting soft or slippery materials, especially when cutting with a slicing or drawing motion. Good examples of where a toothy edge excels are cutting rope, tomatoes or zip ties. Extremely small teeth and a very polished edge are great for push cutting applications like shaving, chopping and carving.

Here are some images contrasting the edge of a knife that’s been sharpened with old, well worn 600 grit diamond plates:

and another that’s been sharpened with fairly new 600 grit diamond plates:

The difference in the width and depth of the scratches is pretty obvious between the new and worn stones and the resultant cutting ability certainly reflects this.

In conclusion: to have a sharp knife, you must first pick an angle that is appropriate for your cutting task and then you must ensure that you’ve done enough work so that your bevels meet at the apex of the edge. If you’ve done both of those things and it’s still not as sharp as you’d like, you can give more time for your break in. You’ll be happily surprised by the results. You can also look at adding some finer grit stones and/or strops to your sharpener as these will allow you to refine your edges further and give you even sharper knives.

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