Thinning Fujiyama

Proper user technique and care is essential to enjoying these high performance knives to their fullest while keeping edge damage to a minimum. Learn how here.
Post Reply
ButlerHoosierChef
Posts: 722
Joined: Tue Oct 31, 2017 9:34 pm
Location: Greenfield Indiana
Has thanked: 68 times
Been thanked: 31 times

Thinning Fujiyama

Post by ButlerHoosierChef »

So I have an older Fujiyama 210mm that has been used alot and it needs thinned or reprofiled and I have never done it but I want to try and do that myself so can someone with alot more knowledge about this let me know the process as well as possibly getting a Kasumi finish. Thank you in advance!
salemj
Posts: 3709
Joined: Thu Jan 26, 2017 9:27 pm
Location: British Columbia, Canada
Has thanked: 197 times
Been thanked: 528 times

Re: Thinning Fujiyama

Post by salemj »

I'm not going to pretend to be an expert. However, it would help anyone wanting to give a pointer or two to know the grind (is this a shinogi or non-shinogi? I'm assuming shinogi if you mention Kasumi...), steel type, and perhaps to see a choil shot and a profile shot. It would also help to know why you think it may need reprofiling (in terms of how it feels in use and if you think it needs adjustments to the front half of the knife).

I do not have (hardly) any experience modifying these knives. But I do a generous amount of experience with a number of different types and editions of Fujiyama knives and can potentially offer some pointers.
~Joe

Comments: I'm short, a home cook, prefer lighter, thinner blades, and own mostly Konosukes but have used over a dozen brands.
taz575
Posts: 4920
Joined: Wed Jan 25, 2017 2:54 pm
Location: CT
Has thanked: 30 times
Been thanked: 1143 times

Re: Thinning Fujiyama

Post by taz575 »

I belt thinned a couple Kono Fujiyama several years ago for Aaron Gibson. A few things I learned:

They use (or at least used to use!) a very shallow hollow grind for the blade road on the wide bevel ones and another slight hollow above the shinogi too, so they were like a diamond profile. Put a straight edge on your blade road and blade "flat" and see if it is very slightly hollow, flat or convex. Decide if it is hollow if you want to flatten or convex it, which will be a lot more work, or leave the hollow at the top and thin just behind the edge and how much you want to remove.

Coarser stones work quicker obviously, but the softer mild steel (I am assuming it is a san mai if looking for kasumi finish) will feel stickier/gummier on the stones than the hard core steel will. Scratches seem to be harder to take out of the soft cladding for some reason, too and where it was slightly hollow, we had to leave the deeper coarser scratches we found so we didn't remove as much material. Sandpaper on a firm rubber backer may be able to get into the gentle curve (if its there on yours) to clean up those scratches.

Kasumi finishes are typically done using Japanese Natural stones; softer muddy ones work well to get into the slightly hollow or low areas of the blade roas (as well as the mud getting in there too). King 800 is a good synthetic stone that can start a decent kasumi finish. Each steel/stone reacts differently, but generally softer stones work better for a kasumi finish. I picked up some EDM stones, but haven't gotten to use them on a blade to see how they finish and if they leave a kasumi or not or if they work well in lieu of hand sanding a blade. One of the many projects I haven't gotten to try out yet!

We went with a belt thinning, removed most of the hollow in the blade grind and the shinogi and convexed the blade on the Kono Blue #2 Fujiyama. I tried a high polish, but the patina was a rusty looking ugly orange, so we ended up acid etching it to force a patina and tone the reactivity down. This is what it looked like after the belt regrind, thinning and etching:
BB4.jpg
BB3.jpg
You can see some of the vertical scratches left from the original grinding, too in the hollow areas. We left those and focused on thinning the blade for performance in a pro kitchen and getting a satin finish on the blade as a whole before acid etching versus spending hours with sandpaper getting every last scratch out and redoing the shinogi or taking too much weight out of the blade. Aaron is a lefty, so I made the left side bevel of the blade more convex and flattened out the right side to make it more lefty biased for him, too, which is why the cladding is much higher up on the right side of the blade and the left the cladding is lower.

I know other craftsmen can thin blades down and keep the original grinds/profiles and stuff, but I have never tried it. Never realized how much they use those large wheels to get crazy shallow grinds that you think are flat until they hit the stones!
salemj
Posts: 3709
Joined: Thu Jan 26, 2017 9:27 pm
Location: British Columbia, Canada
Has thanked: 197 times
Been thanked: 528 times

Re: Thinning Fujiyama

Post by salemj »

What is more crazy, Taz, is that the original scratches of the blade road on a Morihiro are usually parallel to the edge! Think about it: to get that amazing hollow grind, the knife needs to be held perpendicular to the wheel. This means the scratch pattern should be perpendicular to the edge. While the scratch pattern above the shinogi was always obviously purely cosmetic in terms of its angle and consistency (roughly 45 degrees), this basic truth suggests that the scratch pattern on the blade road was also purely cosmetic and actually ground out any of the actual polish from the wheel.

My impression has always been that the scratch patterns they put on these must be from buffers. The original patterns match course finishes—much coarser than the actual grind polish from what I can tell (I'd guess between 220 and 400 sand paper, usually coarser above the shinogi and less course below). I've always assumed the grinding was done carefully on the wheel, that the amount of S grind was dependent on Tanaka to some degree (in the original geometry), and that the finishing was done using some kind of felt buffer wheel with a compound. But who knows.
~Joe

Comments: I'm short, a home cook, prefer lighter, thinner blades, and own mostly Konosukes but have used over a dozen brands.
taz575
Posts: 4920
Joined: Wed Jan 25, 2017 2:54 pm
Location: CT
Has thanked: 30 times
Been thanked: 1143 times

Re: Thinning Fujiyama

Post by taz575 »

That is weird! I wonder if they grind parallel to the wheel for a bit near the edge? Many kasumi finishes are actually bead blasted on, not actually done with stones, so that would make sense that the scratches are hidden until you do a stone polish. I know several of my blades with a kasumi finish were a bead blasted kasumi!
User avatar
enjay
Posts: 474
Joined: Wed Mar 07, 2018 12:54 pm
Has thanked: 173 times
Been thanked: 148 times

Re: Thinning Fujiyama

Post by enjay »

This whole video is very cool and worth watching, but I've timestamped when the sharpener takes over from Tanaka:

https://www.youtube.com/watch?v=5JHZRLer5PI&t=377s
salemj
Posts: 3709
Joined: Thu Jan 26, 2017 9:27 pm
Location: British Columbia, Canada
Has thanked: 197 times
Been thanked: 528 times

Re: Thinning Fujiyama

Post by salemj »

enjay wrote: Thu Jun 23, 2022 9:28 am This whole video is very cool and worth watching, but I've timestamped when the sharpener takes over from Tanaka:

https://www.youtube.com/watch?v=5JHZRLer5PI&t=377s
This is brilliant. It addresses exactly the points I was wondering about above. I'm genuinely surprised that both belts/buffers AND finger stones are used. Clearly the stones are purely cosmetic, whereas the actual grinding and shaping is done by the wheel, belt, and buffer. Thanks for sharing this with the time stamp!
~Joe

Comments: I'm short, a home cook, prefer lighter, thinner blades, and own mostly Konosukes but have used over a dozen brands.
Post Reply