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Sharpening a Chef's Knife


April 8, 2020

Time to Sharpen my Chef's Knife

Today I'm taking advantage of working from home to give some attention to my own kitchen knives. I started with my well used Wusthof Chef's Knife. Using the Edge-On-Up PT50A Tester, I measured three points along the length of the blade and got results from 443, 359 and 480. Not "butter knife" dull, but certainly in need of some work.


Testing Sharpness

We use the Edge-On-Up to test knife sharpness. It measures the force required to cut a piece of certified test media. The lower the number, the sharper the edge. A butter knife is roughly 2000, a new knife is often around 300, while a razor blade can be sharpened below 100. We use this in our shop to measure our results.

Sharpened on the Tormek

For this job, I went to the Tormek T-8. First I put the knife in the SVM-45 Knife Jig and set it on the Universal Support Bar. I adjusted the height of the bar by eye until it looked close. Then I used a marker to color in part of the bevel of the knife. Placing the knife back on the support, I turned the grinding wheel gently by hand. Checking the marker on the bevel showed me where the grinding wheel was contacting the knife. From there a couple of minor adjustments were all that was needed to get the angle just right.

I used the coarse side of the Stone Grader to prep the grinding wheel, then I worked on one side of the knife at a time, grinding until I could feel a burr on the opposite side. When I had the burr across the entire length of the knife, I flipped the knife over and repeated the action on the other side.

Then I used the smooth side of the Stone Grader to change the grinding wheel to a 1000 grit and repeated the process. After that I did one more round using the SJ-250 4000 Grit Japanese Waterstone (this step is optional, but I have the Japanese Wheel so I decided to use it). To finish, I used the T-8's Leather Honing Wheel to create a mirror polish.


Results

After sharpening, I retested the knife on the Edge-On-Up Tester at the same three points. My readings this time were 86, 108 and 168. Definitely much sharper. I was a little surprised by the variation, especially at the tip. A magnified visual inspection revealed a very slight roughness remaining in the tip. The edge I achieved is more than sharp enough for my cooking style (and far sharper than almost any new knife), so I am quite pleased with the results. If it had been one of my woodcarving knives where I demand a more perfect result, I would simply go back to the Japanese and Leather Wheels for a smoother edge. In the meantime, my chef's knife is ready to go back to work.