spot annealing to create hamon line

S

Sharphur

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Sep 11, 2011
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So I'm going to be sending off my first stock removal blades for heat treat soon. I'd like a Hamon line. I can find a service that does the Hamon line if I shop around enough but I have an idea. What if I get it hardened like normal (I plan to use Texas Knife Supply) and then spot-annealed the back edge of the knife? I'd cover the cutting edge with insulating clay, then use a butane pen-torch to heat the blade to anneal temps, then water quench. The insulating clay in theory should protect the cutting edge from the heat but I can't be sure it won't radiate across the steel itself, underneath the clay.

Is this an effective way of making a Hamon line? Will it soften the cutting edge? Will a cryogenic dip be undone on the cutting edge by this method?
 
To anneal carbon steel, time at temperature is needed. Heat to A1, where a magnet wont stick to the steel, then lower the temperature by app. 50 degrees per hour until the steel reaches 400 degrees.

You can "soft draw" the spine of a blade that has been fully hardened by submerging the edge in wet sand or water and then heating the spine to 500 or 600 degrees; this may be what you are thinking of.

If you are using common carbon steels that are in the .8 carbon range it is fairly easy to do your heat treat at home.

Good luck, Fred
 
I think using the clay would produce the opposite effect you are looking for since it would insulate the edge and keep any heat transfered from the spine in the edge. theoretically this would soften the edge more than you want.

Like said above, have the edge in a conductor (water/wet sand) so it pulls the heat out of the edge, thus keeping it cool and retaining the hardness.

wether or not it produces a hamon i dont know for sure, but my guess is that it would not, but again based on theory. I think (!) that a hammon is produced when you have a sharp line that devides the properties of the steel, like hardness or type of steel.

take this with a grain of salt, I havn't made many knives, and none with hammons, so this is all based on reading and deduction.
 
you need to create pearlite. Pearlite is created above tranformation temp. I would be interested to see if you could actually do this but I do not think so. I would recommend waiting until you do your own HT. What steel are you using?? Air hardening steels do not lend themselves to hamons.
 
two billets 1080, one 440c.

Yeah, I thought perhaps that heating the back side to annealing temperature and then cooling it would change its properties as well as give a sort of hamon line. I thought the clay might protect the heat but it would probably just gather it.

I think I'll just live without it until I can get an oven setup to work with.
 
Hamons are an art unto themselves, require alloys with specific properties and very precise HT regimens, and (in the modern age) frankly serve no true purpose other than decoration. You're putting the cart before the horse.
 
I see two problems here (at least):
First, I don't think Texas Knifemaker's Supply will heat treat carbon steel. I might be wrong on this, but if they did, you wouldn't get much of a hamon out of 1080 anyways
Second, you can't get a hamon out of stainless steel

Jason
 
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