Stop, Hamon time...

[Butters]

I hope the image works. Gyuto in 1095. I cut, profiled and half ground 6 blades in 210-270 sizes, thermal cycled them to reduce grain and then promptly broke 4 in the quench (brine). I did the last two in a fast oil and I think that's the way forward for me from now on. There's still plenty of ham in the hamon and I won't put hours of work into something just to have it break.

Post temper hardness is 61RC so should be tough enough for honest work and still fairly easy to sharpen. I think thin sections like knives cool plenty fast in oil so reach full hardness. This needs finishing as it's only at 400 grit, I was just excited as it's my first play with clay and hamons.

 

[Kippington]

That's damn sexy!
I have no doubt that oil would be fast enough at the thicknesses that you're quenching at, although it makes me wonder if the hamon would've followed the clay closer if you had done it in water.
How'd you bring out the hamon? I'm guessing vinegar was involved?
And did you find that the water quenched ones got a sori curve?

Those knives on your workbench look pretty good too!

 

[milkbaby]

Looking good at 400 grit already. What type of oil did you use for 1095? A specific brand and type of manufactured quenching oil?

 

[Butters]

I gave it 10 seconds in ferric just to bring it out, but will polish it to a higher grit then use vinegar or lemon juice, as the ferric kinda makes it look dirty.

I use Excelquench 603, and have 25L while only needing 10. If anyone is based near London (UK) and wants some get in touch.

The water quenched blades did get a sori curve, and that's what cracked them. They all cracked from the edge up, as the spine bent back it put too much force on the edge, which just split. I had taken out the grind marks to 240 at the edge to try and avoid these stress cracks but the 'ting' was almost immediate. I did an interrupted quench which simply interrupted the 'ting' and that blade cracked on the bench before I could temper it. I had maybe 8 hours invested in these by then and that's when I switched to oil.

They're all quite high (53-57mm at the choil) and I think that puts extra pressure on the edge as the spine curves upwards. Perhaps a smaller blade or petty might work in water, or perhaps heat treating the profiled blade before grinding the bevels, so there's more meat there. Tbh if I can get good hamons and straight blades from oil I won't be looking to go back to brine any time soon.

I think with some tweaking of the oil temp and tempering procedure I can get RCs of 63 which is plenty. Any more than that and stuff is just hard to sharpen anyway...

 

[jessf]

Don't give up on using salt water brine. I had just one crack when using clay and salt water and i felt at the time that it was likely do to overheating the steel in the new forge. I rushed the whole process and did it during the day so i wasn't observing colour changes. I switched to heat treating at night only.

 

[Kippington]

You may be right... hell, I use water too, but losing 4 out of 6 in the quench is a good reason to switch to something else that works. :razz:
I'd be using oil if it wasn't so damn messy.

And besides, that hamon worked out really well in oil.

 

[Butters]

The temp is good, I've got a paragon kiln and I've double checked the thermocouple with one I had in my forge. The hamon followed the clay well at the front but less so at the back; I assume it started to crack off as soon as it hit the oil.

I think perhaps I put the clay on too thick, which increased the sori curve, putting more stress on the edge. I saw a presentation by Jesus Hernandez a while back (hosted by Owen Bush) where he discussed hamons, and how important the blade geometry (prior to heat treat) and clay application were to their ultimate success. I'm at the beginning of a long road.

Anyway i'm pretty happy with the result and I think with a bit more trial and a bit less error I can get them where I want them. I'm still tweaking HT on 1.2519 and 14c28n as well making some San mai so it's a time issue more than anything else. Getting a whole day without work or family intrusion is rare.

 

[fatboylim]

Looking good and quite the experience no doubt!

 

[Butters]

I’m glad this baby worked - 265mm at the edge, all straight and true. As before it’s 61RC and western handle, ground for a righty. I’ve gone for an asymmetric grind so I can get it nice and thin behind the edge (under 1mm thick 12mm back from the edge) while still retaining some convexity on the right side to aid food release.
I gave this a quick and dirty polish/etch just to see the hamon. I’ll hopefully get time to finish it up over the next few weeks. A Cocobolo and Blackwood handle should set it off nicely.

 

[TheCaptain]

Nice job! Maybe post some process pictures on the next one?

 

[Butters]

Here’s a shot of some blades with clay before the heat treat.

 

[TheCaptain]

Thanks! Love WIP pictures.