Tempering the spine on O1

panch0

panch0

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Jun 16, 2008
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I have three O1 blades that I have ready for HT. I will probably do this next saturday. The question I have is on drawing back or tempering the spine and keeping the edge hard. I did some reading and came to the conclusion that I need to put the edge in some ice water and use a oxyacetelyne torch to draw back the temper on the spine. I don't have a torch so does anybody have anotherway that a newbie like me could do this after I bring my blades home after HT and tempering them? Thanks in advance.

Oh yea does this create the hamon effect on the blade?
-frank
 
You can use a propane plumbers torch and you don't neccessarily need to dip the edge in water while heating, just take your time and watch the colors carefully, heating the spine only; when the edge draws to the correct color for you, stop and dip the blade in water. You can also use a wet rag to cool the edge as you get the correct color on the spine.

Or maybe I'm misunderstanding you, do you want the edge to be full hardness as quenched? If so, my method won't work.
 
I want the cutting edge to stay at the hardness that it is when you HT amd temper. Lets say RC59. I want to make the spine softer than the cutting edge as to make for a tougher blade. At least that is what I had in mind.
-frank
 
the most controled method is to used refractory cement on the spine this allows the steel to cool more slowly than the blade edge.I havent done this just seen it done and looks like the best way to control in the tempering process. Some people also reheat the knife in the kitchen oven to 450 for 1 hour to take some temper out.
 
hellgap said:
the most controled method is to used refractory cement on the spine this allows the steel to cool more slowly than the blade edge.I havent done this just seen it done and looks like the best way to control in the tempering process. Some people also reheat the knife in the kitchen oven to 450 for 1 hour to take some temper out.
Click to expand...

The refactory cement is only used in the hardening process and has nothing to do with the tempering process. It leaves the spine softer and tougher. Refactory is used mostly to create a hamon.

All blades will need tempered after hardening, which has nothing to do with creating a hamon or drawing back just the spine. In the "as quenched state" the blade steel will be in an untermpered martensite crystal structure. Untermpered martinsite is very hard and very brittle, thus not good for a knife. Once tempered in the oven, the martensite will transform from the untermpered form to tempered martensite which is softer (but still hard enough to hold an edge), and much less brittle and better able to keep from chipping during use.
 
If all you're wanting to do is draw down the temper on the handle and spine while leaving the cutting edge alone on an already heat treated and tempered knife, using the edge in water technique works great to avoid ruining your temper. You can use a small propane plumber's torch as was suggested to draw the color on the handle and spine up past the purple hues. This creates a differentially tempered knife that is fully martensite, but of differing tempers (and thus different hardnesses).

Using clay on the spine results in a knife that is composed of martensite at the edge and pearlite under the clay (differential hardening). This does create different hardnesses and can make great hamons on some steels, but for O-1, it's hard to achieve any type of hamon. In my opinion, unless you just want that great look of a hamon in say a 1084 or 1095 steel, just stick with differential hardening for the uniformity of composition.

--nathan
 
How are you heat treating, panchO? If you are doing it yourself or have input as to how it's done, you could just do an edge quench only and then you won't have to bother doing anything else.
 
A friend of mine does it for me. With time being scarce I will probably temper at home and try to do the differential temper myself.
 
the "temperline or hamon" on O1 tool steel will likely just come out straight and not have any activity. You can always ask Blgoode (USERNAME) how he does his.

I have used a MAPP/OXYGEN torch in the past with satanite (Refractory cement?) and used a paining motion in the areas where the satanite wasn't on on the edge and the line actually came out wavy....but again, not a consistent heating with that little torch.
 
Take a shallow baking pan and put in 1/4" of water. Get a Bernzomatic torch from the hardware store (The JTH-7 is a good choice). You can use MAPP gas for a little more heat, but the propane cans will work just fine.

Sand the blade to a good clean metal surface after the oven tempering is done.I like a 220 grit finish to watch the color move.
Using pliers, or a vise-grip, hold the blade at the tang, resting the edge in the water.It doesn't matter that the whole edge isn't under water. Take the torch and play the flame along just the spine starting at the tang. As you move the flame down the blade toward the tip, rock the blade as you go, to keep the edge in the water under the flame. Play the flame back and forth and watch the temper colors slowly walk down toward the edge (keeping the blade rocking back and forth to cool the edge). The straw color will walk down to near the water, that is good. The darker bluish colors are what you are wanting the spine and tang to have at their edge. When all is right (or if it is moving too fast) just tip the blade over sideways to cool the whole thing. You can re-sand the blade and do this several times until the results are as desired. This will give you a good spring temper on the spine. As with all tempering, never let the edge get blue.If it does, you will need to re-harden the blade.

The hamon is a completely different thing and you won't get one from this treatment.

Stacy
 
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