A new forged 1075 kitchen knife still in polish stage and a quick W1 weeding knife. You can see the sugha hamon at 80 grit before tempering. Weeding knife is done with wet Rutland 2700 degree furnace cement straight into the forge 10 min soak at temperature, interrupted quench 3 seconds in 3 seconds out then straight in till cold. Water temp was 60 degrees with only about 1/8″ of bare blade showing, the rest was coated in cement 1/4″ thick. That’s 1/2″ W1 drill rod from McMaster-Carr. (it’s cheap) It has a tendency to crack without a high enough forging temp and it needs a different quench sequence timing than 1075. The clay held on with no bubbles. It’s a small blade,.. the big machetes are way way harder to do right usually it takes about 30-45 min to just heat it up before the quench.
I usually do a triple temper in a convection gas oven at 400 then 425 and then 450 followed by the freezer down to -10 f. To me that makes more sense ramping up the oven in little steps get a more even conversion in the temper because otherwise why not just leave it in the tempering oven for 3 times the amount of time? I also use a calibrated pyrometer on the steel itself to gauge temps. Oven temp and temper temp of the steel is ALWAYS different,.. for a full soak you are talking all night long,.. and the steel color is absolutely not accurate.
That’s basically a result of my race car fabrication ethos when it comes to knife making. If you approach it with the same care you would use with a “life critical part” or a part that if it fails the driver runs into a wall and get’s killed. That’s my attention to detail with tools and knives.
The Kitchen knife was done with a custom clay mix and the weird thing is the hamon basically is right on that forged in bevel. Clean steel is the key to not having to grind out all the pits which makes the hamon more indistinct. The fully hard layer with simple carbon steels is roughly .065″ or 1/16″ deep. So if you imagine that you are “printing the hamon” onto the blade and it get’s “blurrier” the deeper into the steel you grind you will have it about right. I use Nicholson Black Diamond and Save Edge (farriers) files and you can really feel the difference once you get past that “hard skin”. Testing it out brinell wise we are only talking about a 7-14 points in hardness difference.