Kekoa gyuto started

[taz575]

So Kekoa ordered up a custom gyuto in 80CRV2. This steel is similar to 1085, with some Chromium and Vanadium added to the steel. Specs are around 225mm long, 52mm at the heel, full convex grind.

I ordered the steel and finally got it in, so I started roughing out the profiles for the heat treat process. When doing a convex grind, the spine also gets ground down a bit, so I am leaving these wide to try to keep the full 1/8" at the spine after the convexing is done. I cut out 4 blanks; 3 rough/way oversized profile and 1 rectangle with fat, wide tangs. This gives me something to hold on to while grinding so I can put pressure on the belts.

For the heat treating process, I took some extra steps. 80CRV2 is know for decarb, which is the carbon in the outer surfaces of the steel burning up, leaving a softer, mild type steel that needs to be removed to get to good, hard steel. To prevent this, I used some 321 SS tool wrap foil and put the blades into a pouch of the foil. I also added a paper towel to burn up to use the oxygen inside the packet. The foil pouch prevents oxygen from reacting with the surfaces and prevents the decarb. I normalized at 1650 in a kiln with a 10 minute hold and then removed the blanks and air cooled the steel. Then I brought the kiln back up to 1400 for 30 minutes and let cool slowly in the kiln down to 1200, removed from the kiln and let it air cool. When they were cool, I unwrapped the foil pouch and saw remnants of the burnt paper towel, but the steel looked good with little to no decarb and nice and soft!

But they were warped a good bit. Steel often has stresses in it that will show up with the normalizing process, so I made a 3 point jig to straighten out the now soft blades. Once they were straightened, I painted on a coat of ATP641 on the blades. ATP641 is a liquid substance that dries, leaving a coating on the blade, protecting it from oxygen. Once it is heated and cools down, it falls off, but prevents scale and decarb. I used this to get ready for quenching because I cannot quench in the foil packets since it will slow the quench down too much. After the blades were painted and dried with my heat gun, I got the kiln to 1525 and the blades went in. 1525 for 10 minutes and I started quenching them in 110 degree Parks AAA. After I removed the blades from the Parks quenching oil, it went into a vise with angle iron in it so keep it straight while it cooled down more to keep it straighter.

Once that was done, I wrapped the blades in regular tin foil and popped them into the oven at 350 for 2 hours, then out until they cooled down, then back in for 2 more 1 hr long sessions at 350 for tempering. End rockwell hardness is right around 62!

Here is what the blanks look like after the heat treat process, quenching and tempering cycles!

Next step is to get one or two of these trimmed down profile wise and start grinding some bevels! I always leave oversized and trim down to shape, so two of these will get a lot of steel taken off! I will leave the other 2 oversized and ready to go if someone wants a ~8-10" gyuto that I can tweak the profile to their specs.

[Kekoa]

Yay! Looks like it is going well!

[taz575]

Here is the paper template over the oversized blank. I like to leave plenty of room when I am first starting with it! The last thing I trim up is the overall profile (I leave extra length at the tip and heel for the clean up there) and then do the tang when all of the grinding is done. Much easier to control the blade when grinding with a larger tang and not have to worry about the blade loose in a handle.

[taz575]

Started grinding the gyuto yesterday!

Brought the flat grind about halfway up the blank, which was about 3/8" taller than planned.

Started working the convex up the blade

Taped off the blade to draw closer to the profile to trim it down a bit

[taz575]

Profile, its 240mm long and 54 mm tall IIRC right now, so I still have some trimming to do!

Choil shot:

Did well through some potatoes and keilbasa last night. Tried an onion tonight and it was a little wedgey when doing the horizontal and vertical slices to dice it, so I will try thinning out the tip and bring the grind a bit more up the blade.

[taz575]

Did some more grinding. I started working the convex grind further up the blade towards the spine, especially on the front half of the gyuto. This helped thin it out.

Tried 2 onions and it went nicely through them! It's a workpony, but it was much smoother through the onions. It powered through the peppers. Potato and sweet potato test may be tomorrow afternoon!

Choil shot now:

[taz575]

Did the sweet potato test tonight. The Magnacut S laser and my reground 52100 S laser smoked through the sweet potato and had excellent food release. The blade slipped through with little resistance due to the thin grind and hollow section. The sweet potato felt "soft" when cutting if that makes any sense. These are both much thinner grind wise and stock thickness wise.

The Kekoa workpony did well and powered through the sweet potato, but needed a little bit more effort because its a much more robust grind and thicker spine. It reminded me of my Tanaka Sekiso through sweet potatoes! The grind pushes the food away from the blade nicely, but I am going to push the grind a bit higher to see if I can improve on its performance.

The sweet potato I cut was also noticeably bigger/fatter than the other 2. A guillotine and glide motion went through pretty easily, especially after the initial cut when the slices could fall away from the main part of the potato. Stacking 3 of the thick slices into a stack the and cutting down the stack ( 2 cuts down to make 3 rows, turn 90 degrees and 2 more cuts down to turn each slice into 9 pieces) was very good too since the pieces could be pushed out of the way by the blade as it passed, leaving the stacks standing. It has some power cutting! May also grab a rutabaga and try that next week too since its tall, wide and hard!

[Kekoa]

He he, I like the term workpony. Also sounds like it is going in the right direction if it is turning out similar to a Tanaka, he was one of the makers I had taken an interest in.

[XexoX]

Have you found the kanji for Kekoa so you can hand scribe it onto the knife?

[Kekoa]

I'll have to ask my brother on that one, he happens to be trying to learn some Japanese!

[taz575]

Yesh, work pony was coined by someone else, but its a midweight gyuto with a solid feel to it, but not a workhorse type with a 4+mm thick spine. Going to work the grind up a bit more and get some taper to the spine and then test again!

If you find the kanji, I can probably use the Cricut to cut a stencil and electro etch it onto the blade. Its 62 hrc, so chiseling probably wont work!

[taz575]

Tried to get a better choil shot before going to work today for a double shift:

[Kekoa]

I asked my brother about the letters, he said for foreign words the Japanese usually use Katakana characters instead of Kanji. Kekoa is my Hawaiian middle name and this is what he showed me makes the sounds Ke, Ko, A.

アケコ

This got me thinking of possibly doing it in Chinese because I actually have Chinese blood as well, but I don't know if I can figure out what the letters would be in Chinese.

It would be cool if I could get it to look a little more natural than computer block letter, I could try drawing them with a digital art tool to give it a hand written look, but I'm not sure how easy it would be for you to stencil something that detailed in a fairly small space.

[taz575]

When I looked them up, it was in this order? The backwards C looking character is supposed to be the Ko and the one like the P is the A ?

kekoa katakana.jpg (10.06 KiB) Viewed 1177 times

[aporigine]

When I looked them up, it was in this order? The backwards C looking character is supposed to be the Ko and the one like the P is the A ?

kekoa katakana.jpg

possibly reversed? Iirc it should go right to left.

[taz575]

It could be? I saved the kanakata individually, so I can put them in any order or rotate them to go up or down the blade.

[Kekoa]

You got the order right Taz, I checked with my brother and he said the one he sent me was out of order on accident. So this is right.

ケコア

Right to left is correct for the current writing method in Japan he said, but they used to write top to bottom, which I might do for this. I think I like the look in that orientation.

ケ
コ
ア

[gladius]

You got the order right Taz, I checked with my brother and he said the one he sent me was out of order on accident. So this is right.

ケコア

Right to left is correct for the current writing method in Japan he said, but they used to write top to bottom, which I might do for this. I think I like the look in that orientation.

ケ
コ
ア

---
Wouldn't it then be??

ア
コ
ケ

[taz575]

Did a little photoshopping today! I can't get a straight on shot of the choils of 2 gyuto at the same time and have both be aligned and in focus, so I took some pics and did some editing.

Top is my 240mm Sekiso from Shigeki Tanaka and bottom is Kekoa's gyuto, which is right around 240mm lengthwise so far.

sk3.jpg (30.41 KiB) Viewed 1101 times

You can see what I mean by bringing the grind height further up the blade. The Tanaka has the convex strong at the bottom and flattening out halfway up the blade going towards the spine. Kekoa's gyuto has a little flatter convexing going much further up the blade, so it stays thinner, longer.

[Kekoa]

Wouldn't it then be??

ア
コ
ケ

Oh gosh, my brain isn't working, I meant to say left to right, like we read in English.