In September 2023, I received a batch of Yoshikazu Tanaka shirogami #1 gyutos that we had ordered. As a big fan of minimalist (and of course, it's a Tanaka!) knives, I kept one for myself. While it was a great knife, I wanted to customize it to my exact preferences. The original goal was to simply thin it, but I decided to go all out. So, I turned it into a project knife, with the goal of not only thinning the blade but also removing any low spots and giving it a full convex polish using bench stones.
Figure 1. The September 2023 batch of Yoshikazu Tanaka gyutos. The gyuto is from this batch.
I. Removing low spots and setting the geometry
To begin, I used a Debado #180 stone to remove the low spots and the engraving. Before proceeding with the flattening, I determined where the original sharpener set the geometry of the knife. This is crucial because it helps you know where to blend when progressing to higher grit stones. If you flatten and thin without considering the original geometry, you might accidentally remove the transition between the hira and kireha, resulting in a full flat knife instead of a full convex.
Figure 2. Tanaka gyuto on a Shapton #320.
II. Progressing to the next stones
Once the low spots were removed and the geometry was set, I switched to a Shapton #320. Then, I moved on to medium grit stones, using a combination of Shapton #1000, Morihei #1000, and an unknown soft #1000. The goal at this stage is to remove the scratch patterns from the previous low grit stones while keeping the geometry in mind.
Figure 3. Tanaka gyuto on a #1000 whestone
III. Blending and refining
Next, I worked up to higher grit stones to remove scratches and blend the transition between the hira and kireha, creating a smooth, rounded shoulder. Pressure management is important here to avoid completely flattening the transition. Once the blade is smoothed and the transition is well-blended, it's time to move on to the next stage: achieving a mirror finish on the core steel.
Figure 4. Tanaka gyuto. Blending time.
IV. Achieving a mirror finish
To achieve a mirror finish on the core steel, I used Shapton #2000, Shapton #5000, and King #6000 stones. At this stage, you can give the core steel more convexity by using rocking motions. I recommend doing this on medium-high grit stones like Shapton #2000 for less material removal. Doing this on medium whetstones will unnecessarily remove too much material. In fact, even starting on Shapton #5000 is also fine.
Figure 5. Tanaka gyuto after King #6000. Uchigumori powder was applied on the cladding.
Video 1. Convexity on the core steel
V. Final edge and finishing touches
For the final edge, I used an Aizu stone. Alternatively, ending on a Shapton #2000 is also a great option for achieving a refined-yet-toothy edge. As a final step in the process, I applied another round of uchigumori powder using a felt pad to the jigane (cladding). This helped to create an even cleaner and more refined look on the blade's surface.
Figure 6. Tanaka gyuto on an Aizu stone
VI. Final result
After completing the thinning, sharpening, and polishing process, I'm thrilled with the final result. The blade now features a full convex grind, and all the low spots have been removed. The blade is incredibly thin overall with a nail-flexing thin edge.
As with any project, there were some challenges and learning opportunities along the way. I gained valuable insights which I can apply to future projects. Working on this knife has been a rewarding experience, and I look forward to taking on similar projects in the future.
Figure 7. Choil shot of the Tanaka gyuto. Also shown is the convexity on both sides.
Figure 8. Light patina after some testing
Figure 9. A simple octagonal magnolia handle on the Yoshikazu Tanaka gyuto
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Tips:
- Visualize the process as creating two flat surfaces (hira and kireha), then carefully rounding the transition between them to achieve a smooth convexity.
- Take your time and check your work regularly
- Be mindful of your pressure
- Keep your stones flat
- Use a baking soda mixture to prevent rust
Whetstones and other items used:
- Debado #180
- Shapton #320
- Shapton #1000
- Morihei #1000
- Unknown #1000
- Unknown #2000
- Unknown #3000
- Shapton #2000
- Shapton #5000
- King #6000
- Aizu
- Uchigumori powder
- Felt pad
- Baking soda
- Flitz
No diamond pastes or sandpapers were used in this process.
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Thanks for taking the time to read this blog post. If you have any questions, recommendations, or critiques, I'd love to hear from you! - Fred