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View Full Version : Do most Japanese makers eyeball their heat treats??



rockbox
05-12-2011, 12:02 AM
Every video I've watched of a Japanese knife maker, shows them eyeballing the temperature of the steel by the color of the glow. This even includes Murray Carter. I can't imagine this to be very precise. Would this explain the large difference in steel performance between one maker and the next? This is just my observation from the very limited number of videos I've seen and I could totally be on crack.

tk59
05-12-2011, 12:22 AM
I've noticed the same thing but I bet it isn't as imprecise as it might seem nor would I be surprised if more "advanced" methods were less precise than we might expect. It's just hard to heat something up evenly, period.

rockbox
05-12-2011, 12:30 AM
I think its like people eyeballing the doneness of their steaks. It often produces excellent results especially if its a skilled cook, but it will never be as precise as using sous vide water bath or a simple probe thermometer for that matter.

tk59
05-12-2011, 12:42 AM
That's sort of true but steaks don't glow. The color of the glow actually is very closely related to temperature. It's called a black-body radiator.

JohnnyChance
05-12-2011, 02:53 AM
I would imagine that most of the very experienced smiths in Japan learned from someone (or that person learned from someone) who learned how to heat treat knives when there were no means to taking the temperature of the forge or steel. So yes, they are able to eyeball it pretty accurately. But like TK said, it is more accurate than an untrained eye would assume, and it is hard to heat up chunks of metal evenly. And everyone has their own idea of what the ideal treat is.

Darkhoek
05-12-2011, 05:25 AM
That's sort of true but steaks don't glow.

And if it does it is most likely well done :D

DarkHOeK

DrNaka
05-12-2011, 06:39 AM
It depend on furnace.

If it is a charcoal furnace eyeball the temperature is the only option.
Yoshida san of Yoshikane Hamano said to me that he can see the temperature quite exact in the temperature range of 700 to 800 degree Celsius which would be the temperature for HT carbon steel.
He said also he can not see the temperature for SS which would be around 950 degree Celsius.
He use a temperature controlled gas oven for SS.

Shigefusa only makes carbon steel kitchen knives and use charcoal furnace.
He and his sons eyeball the temperature as well as how uniform the steel is before the quench.
But his yield is not 100%.
I get notice from Shigefusa when my order is in work but only after heat treatment.
He does not make any notice that he began to forge my order because that knife can be lost to HT.

rockbox
05-12-2011, 07:10 AM
From the anecdotes posted on the interwebs, I would probably guess that makers such as Shigefusa or Doi are more particular about what passes as a good heat treat versus a blade they throw away than a maker such as Moritaka or Takeda.

sudsy9977
05-12-2011, 08:21 AM
it's the same as spark testing steel......alot of people think they analyze the steel but alot can and alot can't......ryan

l r harner
05-12-2011, 09:18 AM
one thing you have to know is that the way you see color is dependent on how dark the over all room is too and any change in the lighting can cause problems
i have befor seen makers at hammerins have failed welds or other problems cause there eye was not calabrated to the lighing under the tent

rockbox
05-12-2011, 09:42 AM
I don't mean to say that this is a bad way to do it, but it does require a lot of skill and experience to do correctly and consistently. This is probably one of the reasons we see such a big difference between performance of Japanese knives using the same steel. It is probably also the reason why most makers specialize in one steel. Most American makers use digitally controlled heat treat ovens and even I can do a proper heat treat if someone smart tells me the temperature and time.

rockbox
05-12-2011, 10:05 AM
one thing you have to know is that the way you see color is dependent on how dark the over all room is too and any change in the lighting can cause problems
i have befor seen makers at hammerins have failed welds or other problems cause there eye was not calabrated to the lighing under the tent

I noticed Carter turns off the lights probably for this very reason.

Lefty
05-12-2011, 10:15 AM
So Butch or any other makers on here. How would Carter (or any old-school ht'er) handle a blade that is heating quite a bit differently from point to point?