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Hi guys. Finished a new blade today. 1095 with hamon quenched in warm water then warm oil. First time using Satanite and it followed the clay pattern. Also first time using my new JF#1 burner. Works great. After the blade turns red, even on the lowest setting it keeps the blade bright red.

Anyway, I need opinion on a few things:

1: What do you guys think about the Hamon? Good? Bad? Where does it need to improve? Constructive criticism welcome.

2: On all my knives the Hamon is more clear on one side. The side when the blade is lying flat and the tip is pointing to the right. Its clearer on that side on every knife I've made. Why could that be?

3: In the two pics of the close ups, there's thin cracks on each side of the blade. I'm sure they're cracks because I can feel them with my nails. They became more obvious when I got to the finer sand paper. Why would the blade be cracked in that area?

4: With the light on, the Hamon doesn't show well, unlike my previous knives. Why?

5: Not the best polishing job for 2000 grits. I used Gator sandpaper from Lowes instead of 3m. Is Gator inferior or is it me?

Anything else I need to work on?

knife1.jpg

knife2.jpg

knife3.jpg

knife4.jpg

crackedblade1.jpg

Close up of the blade show cracks on one side

crackedblade2.jpg

Close up of another side showing the thin cracks

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I like the blade profile. You are obviously doing most things right!

 

Hamon appearing sharper/clearer on 1side may indicate the blade didn't heat evenly before quench, or that it didn't cool evenly during the quench.

 

Uneven heat is easy to do with propane forges if you leave the burner on and don't rotate the blade in the forge. Either rotate fequently, or bring the forge walls to an even heat then cut the gas and use the residual heat to bring the blade up to temp more evenly.

 

Uneven cooling could be due to not entering the quenchant edge or point first, but I am guessing you already know that. If your clay pattern or thickness is not identical on both sides, they will cool slightly different and the side with thinner clay, or the clay line further from the edge will have a bit less distinct hamon due to residual heat from the extra clay on the other side.

 

The cracks may be due to a lot of things, uneven quench stress, overheating while grinding with a worn belt, general grinding stress not fully relieved when normalizing before the quench, forging too cold etc. ... Hard to tell without a bit more info on the rest of your process.

 

James

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I quenched tip and edge in first and I did my best to get the clay even on both sides. So I think it is the uneven heat treat because I don't turn the blade at all once it is in the forge. I'll keep turning the blade every few minutes from now on.

I use stock removal for my blades. It's strange to me that the cracks only happened in the front. I didn't normalize the blade this time after profiling and went straight to heat treating. I'll be sure to normalize next time and see if that helps.

Thanks James

Imad.

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I didn't normalize the blade this time after profiling and went straight to heat treating.

 

Normalizing is part of heat treating! And definitely rotate your blade in the forge.

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Jerrod, it's been a few months since I heat treated the blade but I think first I heated the blade up and let it cool down to black and then heated it to bright red and quenched it. It's been a few months so not sure.

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Personally, I would never trust the mill to supply it in the most refined state. After all, why would they? For stock removal projects, since you apparently have a HT set-up, I'd suggest giving it a triple normalize, then at least 2 more after all the removal right before quench.

 

Also, what does the distal taper on the blade look like? I.E. How thick is it where the cracks are? It looks like the cracks are at the edge of where your clay was. Is that right? How thick was your clay? If you are getting too great of a cooling rate difference (no clay up against very thick clay) it may cause enough stress to tear apart/crack there. What was your pre-quench polish like? If there is a groove that could act as a stress concentrator and cause a crack during quench.

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@Jerrod.

Distal taper is not very thin. I need to work on making my blades thinner. It's fairly thick where the cracks are. The clay wasn't very think. Not even 1/8th". Maybe a little thicker than 1/16". Pre quench polish was coarse grit to help the clay stick. All the scratches were parallel to the edge but the cracks are perpendicular to the edge and a little curved as you can see in the close ups. All the cracks are where the clay ended and there's a bunch towards the tip. So basically all the cracks are where there was very little clay or no clay. Could this be because the area near the tip have gotten too hot compared to the rest of the blade ?

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I'm not sure what to tell you. Sounds like you're doing everything right. I'm thinking it has to do with the cooling rate at that area. It could be that you were too hot and cooled too quick. Could be something else too though. Sorry we couldn't pin it down better. Maybe someone will see this who has had this happen and figured out the why.

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@Jerrod.

Distal taper is not very thin. I need to work on making my blades thinner. It's fairly thick where the cracks are. The clay wasn't very think. Not even 1/8th". Maybe a little thicker than 1/16". Pre quench polish was coarse grit to help the clay stick. All the scratches were parallel to the edge but the cracks are perpendicular to the edge and a little curved as you can see in the close ups. All the cracks are where the clay ended and there's a bunch towards the tip. So basically all the cracks are where there was very little clay or no clay. Could this be because the area near the tip have gotten too hot compared to the rest of the blade ?

 

 

I'm not sure what to tell you. Sounds like you're doing everything right. I'm thinking it has to do with the cooling rate at that area. It could be that you were too hot and cooled too quick. Could be something else too though. Sorry we couldn't pin it down better. Maybe someone will see this who has had this happen and figured out the why.

 

I think we have a reasonable answer right here. I have experienced similar cracks in thicker than average cross sections that had been heated from one side. On quench the different cooling rates cause cracking, primarily on 1 side, but occasionally on both. the fix for me was rotating the knife while heating and occasionally edge quenching to prevent the edge from getting too hot before the spine is ready. To be extra safe, it wouldn't hurt to use a single quench in the oil rather than transferring from water to oil.

James

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I'm a bit paranoid, but I rotate a couple times per minute rather than once every couple minutes. On the other hand, paranoid seems to work because I haven't lost a blade to the quench in almost 2 years. Lost several to grinding mistakes though. ;-(

I occasionally use a plain water quench for 1095 and W1/W2, such as when demonstrating clay quenching techniques at the Blacksmith's Guild.1 of the 2 demo knives I did last summer warped, but neither developed any cracks.

However, my preference for nice hamon formation on those steels is a brine quench (salt water). There are a lot of good "recipes" for the brine salts, I happen to use water softener salt added to warm water until no more will disolve.

Oil quenching is the safest option and I have seen a lot of nice hamons on water quenchable steels that were quenched in a fast oil, but haven't done it myself so can't give you more specifics.

As another possible option, I have gotten some nice hamon formation on 15N20 with a 2-3 second dunk in hydraulic fluid pre warmed to 160F and then transfering to lukewarm water.

James

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I'm not sure what your forge design looks like, but when heat treating, I have to run my forg with as little gas pressure as possible and with the door off to keep it down near 1500f. Even at that, I'll have to shut the gas off every now and then because my forge temp is creeping up too high.

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I'm not sure what your forge design looks like, but when heat treating, I have to run my forge with as little gas pressure as possible and with the door off to keep it down near 1500f. Even at that, I'll have to shut the gas off every now and then because my forge temp is creeping up too high.

 

I'd be surprised if loosing heat will be a significant issue for you.

Edited by Brian Dougherty
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  • 2 weeks later...

Cracks at the front of blade, near edge of clay...

 

here are three things I have learned that will help a LOT with that.

OK, 4.

 

1. normalize as Jerrod said. He can out heat-treat most of us in his sleep.

2. put a thin wash of clay (like literally one grain of clay thick) over the whole blade, then apply the clay to help with the hamon.

3. leave the tip a little thicker and just plan on grinding part of the distal taper in.

4. watch out, the tip will always want to get hotter than the rest of the knife. Two things to do to help.

a. push the blade WAY into the furnace, so the hot jet of gasses is blowing just in front of the ricasso

b. move the blade forward and backward in a stroking motion when you get close to critical temp

c. take the blade out and just let it cool in air for about 5 seconds several times while you are heating, the tip will cool the fastest.

d. actually quench the tip a couple of times, just the tip, when it turns red before the rest of the blade is red. Make sure you are WAY below critical when you do this. But, I have seen vids of Ed Caffrey doing this, and I do it often when I use a propane forge for heat treating. Just jab it into the water or oil (oil is better) for a second (just one) and pull it out. Even less is fine.

 

The point of all of these strategies is to have the tip not much hotter than the rest of the knife when you take it out of the forge to quench. Just a little hotter in the forge is ok, but when you take it out, if the tip is a lot hotter, let the blade cool some (just about 10 sec) and give another try and ramping up to proper temp.

 

If the blade doesn't look to be an even temp, don't quench. Just let cool a very small amount to equalize and heat more uniformly by stroking the blade and hiding the tip away from the flame. For 1095, extra time above critical while you equalize the temps is just a soak. It is actually good to stall just above critical with 1095 or W1 or especially W2 for a minute or so before you quench.

 

you now officially have the hamon sickness. There is no cure. It can be reduced in intensity, sometimes, by pattern welding. Unfortunately, that treatment often leads to the most virulent version of the disease. The dreaded, "hamon and hada," sickness. It has been the ruin of many good men.

 

 

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1. normalize as Jerrod said. He can out heat-treat most of us in his sleep.

 

Thank you very much, but let's not go overboard here. I understand the mechanics pretty well, but there are a lot of steels used for knives that I just don't have any experience with.

 

The tips on letting the blade air cool for a few seconds is a really good one. The heat transfer of the metal itself is pretty good, and still air not so great. This lets things even out pretty well. I get the impression that the blade is being placed in a closed forge, hence only wanting to rotate the blade every couple minutes for fear of losing too much heat. If this is the case then that certainly makes things a little more difficult there, but it does make un-even heating less likely. Personally, I heat the tang end first and tip last, with the sawing motion of the blade in my vertical pipe forge.

 

Uniform heating and cooling at the proper rates eliminates most problems. This of course eliminates the possibility of a hamon. Balancing of evils, the true art of heat treat.

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Not to highjack the thread here, but I found it interesting that you recommend normalizing stock removal knives Jerrod. Most of what I have read say its unnecessary, though the way you put it definitely made me say "DUHH" of course the mill isn't giving me the most refined steel. But I was wondering if you could elaborate on the triple normalization. I know it is a standard practice for knives, but of the industrial literature I've read I don't see it ever mentioned above one normalization cycle. And the only explanation I've heard for three is that when a blade is forged that it introduces more stresses than what is common in an industrial setting.

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Kevin is absolutely right in everything he said. Because i for one am a huge Hamon freak if no one else can tell Kevin will vouch for me.

 

Now my experience with cracks was due to over heating the tip and having the hardened steel separate from the soft steel, and I mean literally the whole hardened edge fell off the blade.

 

Now your forge setup, do you have the flame coming in from the side making a swirling flame in the forge? Or is it just straight down on the steel? The first is the best way to go as it places the heat around the blade and is more even. The second way is not very good for what we do as you can burn the steel and the heat is generally more localized.

 

Now get your self a big bag of vermiculite and use this as part of your normalizing process. I do this on the my third normalize I place the blade in the container of vermiculite and bury it and then cover it. I let it set over night as the vermiculite is an insulator and will allow the blade to cool very slowly, this will make sure your blade is dead soft.

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Not to highjack the thread here, but I found it interesting that you recommend normalizing stock removal knives Jerrod. Most of what I have read say its unnecessary, though the way you put it definitely made me say "DUHH" of course the mill isn't giving me the most refined steel. But I was wondering if you could elaborate on the triple normalization. I know it is a standard practice for knives, but of the industrial literature I've read I don't see it ever mentioned above one normalization cycle. And the only explanation I've heard for three is that when a blade is forged that it introduces more stresses than what is common in an industrial setting.

The purpose of a normalization is the removal of stresses and grain refinement. Now, the cooling will induce some stresses, but all stresses from forging should be removed in the first normalization run. That means that the following cycles are really just for grain refinement. After the third cycle it is pretty hard to show that more cycles would help; diminishing returns. Some would argue that 2 is plenty sufficient. I would agree that 2 is possibly good enough, but I do several (let's say more than 4) on every blade I do (which isn't many) as I really like watching the re/decalescence with the blade and getting a good feel for it before the quench. For those that don't watch for this, you are doing things wrong! You have an opportunity to see something that cool and you don't? Just wrong! B) As to why industry doesn't do it: The added cost (both thermal energy and time) does not outweigh the benefit. As custom knife makers we strive for a higher quality than is economical for industrial manufacturers. They know they could make better quality and how to do it, but they would have a harder time selling enough of the more expensive knives to make their target profits.

 

Imad - Please do share with us a bit of what your heat treat set-up looks like.

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Those particular cracks look a lot like the blade was forged heavily to cold at some point, stress and heat treating cracks tend to be straight, when they form in groups like this with a crescent shape to them it most often is because the steel had some major movement applied to it when it was a lot cooler than ot should have been. They often do not appear at all until after the heat treat, and very often around point areas where the profile of the blade has had radical changes made...ie hammering in the point profile.

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I use stock removal for my blades.

 

Not likely to be from forging too cold in this case, though it is indeed possible that the bar was cracked before he got it.

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Well, did not realize they were stock removal... Wierd...those are pretty typical of fracturing from cold forging.

Hmm.

I've seen the same kind of surface cracking in off the edge, occasionally, from blades being overheated going into quench, but not nearly as often.

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