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Heat treating my first blade
#11
Cool, thanks!
Being a newbie, I leave a lot of material behind before HT, like .030-.050.
I would rather spend more time working slowly (controlling heat) on the edge after HT, than deal with warping and not having enough material left to make a proper edge.

I have been considering experimenting with building a two sided box (which isn't really a box at all).
Just two plates of 304 stainless at 3/16" thick and 1/4" apart, with tabs holding them together at the corners.
Blade goes in middle (not touching).
Quench the whole apparatus.
Seems that the radiant local heat from the stainless plates would at least give me an extra second of margin.
Also, might help with the 'straight in' principle on the HT, just because of the extra weight.
Of course, it will affect the quench oil temp as well. Perhaps adversely.

I watched Mark's video on differential heat treating and definitely will be doing that on my next blade.
It was easy enough to control the heat affected zone on the Nikiri to keep the edge 'hard' and temper the spine.
But, a smaller blade would be pretty tough to control.
Love the differential method!
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#12
Mr. Mark,

Sorry, no such knowledge. It was loud, hot, and big; not something I would install in the home garage with the car.  Sad  It was fascinating to watch.

Ken
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#13
Wade, I can't see how this could be an issue for you. A whole second is quite a while in reality. It probably doesn't take much more than half that, and you probably have at least two seconds before it could affect a .030" edge at all.

Another thing is that the edge cools fastest too, which actually has a worse effect on the blade. Cracks usually appear from the edge. Probably has to do with martensite expansion. 

If you aren't getting the right hardness, set your kiln 25-50* hotter. If there's no gain, go back down and temper it less. There's a solution or a limit to everything. 

I understand you don't have ideal conditions. I think I can envision your disconnection from the blade, as you seem concerned with the blade going "straight in". The only concern is that you don't put side load on it. 

That, and I always keep the blade moving. When you see the heat waves coming off the blade in the (hopefully you use clear) oil, you will see a heat shield form around the blade, and you'll understand why you need to keep the blade moving                            

You can quench at whatever angle you want, and your quench tank allows. Many use long, thin tanks and quench "edge down". Samurai swords and edge quenching are two examples.

It's easy to overthink everything at first. Jeez! You haven't been at this long enough to know the right questions!  Big Grin
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