Polishing Questions

So up until now I have generally just been concerned with tending to the cutting edges of my knives, but as I acquire more wide and single bevel knives, as well as natural stones, I'm starting to have more of an interest in polishing, and the finish left on the face of my blades.

As such, I have a few questions about polishing basics, techniques and tools used.

Something that I have come across and am unsure of how to go about tackling, is how to get a consistent finish on a face that isn't flat. Such as on my kono fujiyama blue #2, which I'm sure some of you know isn't a 'true' wide bevel, so when the blade road is put flat to the stones, I grind parts near the edge, and near the 'shinogi'. Is the use of fingerstones the only way to get a consistent finish? The same problem arises with any blade with any concavity, such as an 's' grind, or just any overgrind I suppose, so how do you approach this?

Any and all polishing tips and advice welcome! Thanks kkf!

When I've bought new single bevel knives I spent a good deal of time flattening out the blade roads with diamond plates and low grit stones until they were uniform. You don't have to do it all in one session but I always have. The king 800 and gesshin jinzo aoto leave a nice even finish on these wide bevels. It is also said that the cheap single bevel knives will need the most work done in this area and I've found this to be true. Though nothing handmade is ever perfect so even expensive wide bevel knives will need some work.

With a single bevel however you will generally be working with a convex road, such as on a hamaguri edge, and so it is possible to get every part of the face in contact with the stone. But on a double bevel knife with a concave aspect to the grind how does one go about this?

IMO, that's a big part of why I'm not a huge fan of S-grind...I'll take a flat grind with convexity every time. S-grind does cut well when new, you just have to convert the knife to a flat grind as you sharpen your way through it. If you care about the finish (I don't so much), you've already figured out to use finger stones...you can also work slowly and put heavy pressure on the parts that are hard to touch to get as close as possible before you go to finger stones.

Jacob_x said:

With a single bevel however you will generally be working with a convex road, such as on a hamaguri edge, and so it is possible to get every part of the face in contact with the stone. But on a double bevel knife with a concave aspect to the grind how does one go about this?

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Not necessarily. There are low spots on both types of blades. These take the longest to work out because you have to grind down the entire surface in order to get things even. Once everything is all flat is when I start the hamaguriba process on single bevel knives or my regular sharpening process on double bevel knives. Somewhere on this forum are pictures of my itonomon 210mm wa petty which shows the nice even blade road I created on both sides. Of course my YouTube channel has a video demonstrating hamaguriba sharpening on my deba I think.

Thanks for the words guys. Think a lot of my further questions are being answered by reading Matus' fingerstones thread... Just was unsure I wasn't missing a trick somewhere along the line.

using a very muddy natural like a aoto is posible to get a pretty even finish on a very convex single bevel, but if you are going onto finishing stones it will look streaky on harder stones. Most Japanese knife makers either finger stone, sand blast, hand sand, or etch for that new knife kasumi look.

Always puzzled why 240 grit paper can get you somewhat of a smooth and reflective looking finish on some steels, but 1000 grit will not...

Here is the picture of my itonomon 210mm wa petty after I flattened and polished it. The stones used on the blade road were gesshin 400, king 800 and gesshin jinzo aoto. What I like is that all three provide a nice mud for you to play around in. Using light pressure after you work up a good mud seems to work well. Then for the edge I used a bester 1200 and a suehiro rika 5k and stropped on felt loaded with diamond. My standard double bevel edge.

Hi, new to the forum, and working on my j-knife sharpening skills. Had the same question as the OP and found this thread. Hope you can clarify a question/concern: when flattening a wide bevel (on a double beveled knife) in order to achieve a uniform finish, does one not also materially move the shinogi line upward in this process? Or is it generally negligible? Example pic below of a Tanaka Ginsan that I tried to clean up the primary bevel on, after getting some scratches on it with my novice sharpening skills. Seems to go from concave to convex, and back again. The partial finish is from a Takashima. If I start working this bevel with coarse stones or diamond plates, isn't it going to widen noticeably? Or have I already screwed this knife up?


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@phoosty if you are working on a slightly concave wide bevel, then most likely yes - in the process of flattening it, the shinogi line will be moved up. That's not a problem.

Not to worry. Over time and with heaps of pressure incorrectly applied you might move the shinogi up disproportionately to the bevel you're trying flatten. It would take years of regular bad sharpening and is more of a thing to watch for with single bevels.

Lest you end up with something like this:











Picture credits thanks to TOGITOGI

While the cross sectional views apply to single bevels, the method for maintaining shinogi proportions still apply. Have at it with your coarsest stone, you won't mess it up. My Tanaka's factory bevel was a shitshow and after a year of chipping away at it little by little, it's nearly flat and even

1 yr ago



Now

The "lest you end up with this" picture you posted is horrifying.

And that's after a rescue job by a professional sharpener.

I have the same knife so I've given some thought to thinning and refinishing. The spine has essentially no distal taper until it hits the grind at the tip. So I thought maybe I would thin the blade towards the tip. Also like your knife the bevel was not evenly ground and the shinogi line was uneven. It seems these knives are good cutters because they have great core steel with good heat treatment, a heavy spine, are thin behind the edge with a concave bevel.
So could I improve it's performance? Maybe. Do I want to thin another stainless clad knife? No No . Thinning soft stainless cladding is as much fun as walking through the woods all night with wet socks and blisters. I think Badgertooth would agree.
If you're not happy with it's performance you'll learn a lot by flattening the bevels. If the appearance of your knife is your main concern you my want to consider different finishing options such as sanding the blade from heel to tip. You could use scotch bright pads, finger stones or stone slurry to get an agreeable finish on the bevel.
Thought I'd chime in because I really like the Tanaka ginsan gyuto. A cook's knife that punches above it's price point.

Thanks all, makes sense. And the knife is cutting beautifully, I just wanted the esthetics to match.

Badgertooth said:

And that's after a rescue job by a professional sharpener.

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The stuff of nightmares