Hello!
Backstory:
I recently purchased a Kemadi bulat gyuto from BST. It came a bit thicker behind the edge than I prefer (I measured 0.3mm-0.4mm at ~1mm behind the edge), so I wanted to thin the knife to make it cut better and refinish it to make it look good again after the thinning. For clarity: The seller was wonderful to deal with, and the knife came exactly as described; I just prefer knives that are very thin behind the edge.
Original pictures:
Thinning:
I did most of the thinning with a Nano Hone 70µm stone, but I also used a Suehiro Debado MD-20. These stones are pretty similar to each other. I have a love/hate relationship with them. They cut really quickly, don’t load up, don’t dish too fast for coarse stones, and don’t leave scratches that are super deep, which is nice, but they are both fairly soft (on the scale of all stones), which causes low spots to reappear on harder stones in my polishing progression and is really frustrating. To me, it seems like the NH70µm stone cuts at approximately the same speed, feel nicer, feels slightly softer, dishes slightly faster, and leaves noticeably shallower scratches compared to the MD-20. Do you have any recommendations for harder/more precise coarse stones that still cut quickly?
The thinning went well, and I got the knife to a thinness I was happy with in around 3-4 hours (~1.5 hrs per side). The stones cut well, and the work seemed to go by quickly. The stones were able to touch all parts of the bevel.
Here are some photos from thinning:
Messaging Kemadi for advise:
After thinning, I DM’d Kemadi on Instagram for advice on etching, and he really nice and helpful. He recommended polishing the knife up to almost a mirror finish and then etching the knife with ferric chloride for repeated cycles of 10 minutes of etching, washing with water, and polishing/partially removing the etch.
Coarse scratch removal:
After thinning, it was time to start cleaning up the coarse scratches on the bevels. This was a huge contrast to my experience thinning. I tried using a Shapton Glass 500 (my go-to stone after coarse stones), Naniwa Pro 400 (a nice, slightly softer alternative), and a Shapton Glass 320 (mine feels like a POS. It seems to load up very quickly and stop cutting on every knife I try it on for polishing. Do you have that problem with the SG320?). All three of the stones felt like they would load up and cut really slowly, which was expected with my SG320, but I have never run into this issue with the SG500 before. What seemed to be most effective with the stones that I had was to refresh the stone surface and build up some slurry with my diamond plate, polish until it felt like the stone wasn’t cutting well anymore, and repeat. This process took a long time, and many coarse scratches remained. Because these stones are harder than my coarse stones, low spots reappeared on the bevels (near the shinogi in the center of the left bevel and near the shinogi at the heel on the right bevel).
The stones that I was working with weren’t doing a good job. I don’t know why, but I think that it might have been caused by the tall bevel/large surface area, mono-steel construction instead of san mai, and maybe the makeup/matchup of the steel and stones. I thought about ordering a softer stone for this step, like a Suehiro Cerax 320, but I was impatient, so I used some sandpaper to get most of the coarse scratches out and create a somewhat even finish. I know that there are coarse scratches left and the final result isn’t perfect, but I just wanted to experiment and try etching out. I can always start over and do a higher effort polish in the future.
Polishing:
I mostly used synthetic stones for my polishing progression, but I did try a natural stone or two. (Sorry, no pictures for this section)
After the stones I mentioned above, I used the following stones: Cerax 1k, JNS synth red auto, Morihei 4k, Morihei 9k (all permasoaked). Because of the remaining low spots, I gathered mud from each stone as I was using them with pieces of felt that I used to even out the polish and reach the low spots that the stones weren’t touching. The Cerax 1k brought out the wavy banding the most out of those stones. I tried a Aiiwatani kiita koppa at some point, which was able to bring out some of the banding, but I think that I just went to the Morihei 9k instead after trying it.
After the stones + mud on felt. I rubbed the bevels on some balsa with diamond spray on it to give it a bit more shine and evenness.
At this point, I had arrived at an okay base for etching.
Etching:
I looked into ferric chloride, but I didn’t really want to use it. Because I was just experimenting with techniques, I wanted to try etching with vinegar first because it is safer and cheaper, and I think that the results ended up being pretty good. All of the tips/techniques in the Etching Q.s thread were interesting and helpful to read.
I put 5% acidity white vinegar into a tall plastic vase, and left the knife in there for a while. I did a few “cycles,” but I didn’t really follow much of a systematic plan/technique. I left the knife in there for ~2 hours, polished the knife with natural stone mud on a felt pad, put it back in the vinegar for ~1 hour, tried polishing with 2k sandpaper, put it back in the vinegar for another hour or so, and tried polishing it with natural stone mud and 5000 grit sandpaper.
The following post will include pictures of the results with my technique, if you could call what I did a technique, and a little written conclusion.
Backstory:
I recently purchased a Kemadi bulat gyuto from BST. It came a bit thicker behind the edge than I prefer (I measured 0.3mm-0.4mm at ~1mm behind the edge), so I wanted to thin the knife to make it cut better and refinish it to make it look good again after the thinning. For clarity: The seller was wonderful to deal with, and the knife came exactly as described; I just prefer knives that are very thin behind the edge.
Original pictures:
Thinning:
I did most of the thinning with a Nano Hone 70µm stone, but I also used a Suehiro Debado MD-20. These stones are pretty similar to each other. I have a love/hate relationship with them. They cut really quickly, don’t load up, don’t dish too fast for coarse stones, and don’t leave scratches that are super deep, which is nice, but they are both fairly soft (on the scale of all stones), which causes low spots to reappear on harder stones in my polishing progression and is really frustrating. To me, it seems like the NH70µm stone cuts at approximately the same speed, feel nicer, feels slightly softer, dishes slightly faster, and leaves noticeably shallower scratches compared to the MD-20. Do you have any recommendations for harder/more precise coarse stones that still cut quickly?
The thinning went well, and I got the knife to a thinness I was happy with in around 3-4 hours (~1.5 hrs per side). The stones cut well, and the work seemed to go by quickly. The stones were able to touch all parts of the bevel.
Here are some photos from thinning:
Messaging Kemadi for advise:
After thinning, I DM’d Kemadi on Instagram for advice on etching, and he really nice and helpful. He recommended polishing the knife up to almost a mirror finish and then etching the knife with ferric chloride for repeated cycles of 10 minutes of etching, washing with water, and polishing/partially removing the etch.
Coarse scratch removal:
After thinning, it was time to start cleaning up the coarse scratches on the bevels. This was a huge contrast to my experience thinning. I tried using a Shapton Glass 500 (my go-to stone after coarse stones), Naniwa Pro 400 (a nice, slightly softer alternative), and a Shapton Glass 320 (mine feels like a POS. It seems to load up very quickly and stop cutting on every knife I try it on for polishing. Do you have that problem with the SG320?). All three of the stones felt like they would load up and cut really slowly, which was expected with my SG320, but I have never run into this issue with the SG500 before. What seemed to be most effective with the stones that I had was to refresh the stone surface and build up some slurry with my diamond plate, polish until it felt like the stone wasn’t cutting well anymore, and repeat. This process took a long time, and many coarse scratches remained. Because these stones are harder than my coarse stones, low spots reappeared on the bevels (near the shinogi in the center of the left bevel and near the shinogi at the heel on the right bevel).
The stones that I was working with weren’t doing a good job. I don’t know why, but I think that it might have been caused by the tall bevel/large surface area, mono-steel construction instead of san mai, and maybe the makeup/matchup of the steel and stones. I thought about ordering a softer stone for this step, like a Suehiro Cerax 320, but I was impatient, so I used some sandpaper to get most of the coarse scratches out and create a somewhat even finish. I know that there are coarse scratches left and the final result isn’t perfect, but I just wanted to experiment and try etching out. I can always start over and do a higher effort polish in the future.
Polishing:
I mostly used synthetic stones for my polishing progression, but I did try a natural stone or two. (Sorry, no pictures for this section)
After the stones I mentioned above, I used the following stones: Cerax 1k, JNS synth red auto, Morihei 4k, Morihei 9k (all permasoaked). Because of the remaining low spots, I gathered mud from each stone as I was using them with pieces of felt that I used to even out the polish and reach the low spots that the stones weren’t touching. The Cerax 1k brought out the wavy banding the most out of those stones. I tried a Aiiwatani kiita koppa at some point, which was able to bring out some of the banding, but I think that I just went to the Morihei 9k instead after trying it.
After the stones + mud on felt. I rubbed the bevels on some balsa with diamond spray on it to give it a bit more shine and evenness.
At this point, I had arrived at an okay base for etching.
Etching:
I looked into ferric chloride, but I didn’t really want to use it. Because I was just experimenting with techniques, I wanted to try etching with vinegar first because it is safer and cheaper, and I think that the results ended up being pretty good. All of the tips/techniques in the Etching Q.s thread were interesting and helpful to read.
I put 5% acidity white vinegar into a tall plastic vase, and left the knife in there for a while. I did a few “cycles,” but I didn’t really follow much of a systematic plan/technique. I left the knife in there for ~2 hours, polished the knife with natural stone mud on a felt pad, put it back in the vinegar for ~1 hour, tried polishing with 2k sandpaper, put it back in the vinegar for another hour or so, and tried polishing it with natural stone mud and 5000 grit sandpaper.
The following post will include pictures of the results with my technique, if you could call what I did a technique, and a little written conclusion.
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