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Olorin

Re-softening a clay tempered blade

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I have a knife I have been working on and just did a clay heat treat, but alas the blade warped and I didn't notice before it cooled down too much for me to do anything about it. I then heated it to critical temp. or just below it and left it to cool in the forge. Does anyone have any tips for softening a differentially hardened blade so that it won't crack in the next quench? A simple list of steps on annealing and normalizing to get the best result would be appreciated.

 

PS. I used the search function on the forum but couldn't find anything specific. And I searched on Google but didn't find anything helpful either.

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no need to anneal.  Soften to straighten, normalize 3X making sure it is still straight, then harden with clay coat again

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I have a suggestion for the future.  Unless the warp is significant, you can usually take it out during the temper cycle by means of a jig that utilizes the 3 pin method for straightening.  As with most things there is a little bit of a learning curve with regard to how much force to apply to the blade to remove the warp without breaking the blade.  Assuming the differential hardening process left you with a reasonably tough spine, the risk of breaking the blade should be minimal and you wouldn't have to take the chance on an additional quench that way.

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Steve thanks that helps a lot!

 

Buzzkill, yeah I was thinking about the three pin method. I'll have to put something together for next time. Thanks!

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As an addition to the three pins, you might also think about this: depending on the alloy you're using, as well as what you're quenching in, you have a small window after the initial quench to straighten the blade while it's "hardening." No, that's not at all the technical term, but I'm trying to keep this relatively simple. And by small window, I mean something in the order of 6-10 seconds, if you're Super lucky and careful. I usually leave a blade in the quench for a 6 count, check for straightness, and if it's warped I'll stick in a vise, or if I haven't gotten rid of them again, I'll put it between sections of angle iron (I like aluminum for it, but steel works quite well) and clamp it somehow. I've also just lightly hammered it straight on a stump or other block of wood, but I don't recommend that unless you're feeling froggy...still don't do it. The angle works better on longer blades, but it's effective regardless. It's a little sketchy and takes a lot of practice to get down, but I've yet to crack a blade, let alone break one doing it that way. Using the pins during a temper cycle is less sketchy, but doing it the way I described gives you a little more plasticity with regard to the metal. Ideally, conditions would be ideal enough for warping to not be a problem in the first place, but that isn't the case as often as anyone would like, and most would admit.

I don't do a whole lot of differential hardening, but it shouldn't make a ton of difference doing it that way with something knife to big knife sized. At least I don't think so.

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 Bob Brandl, oh I never thought about angle iron, I'll have to try it. I've done a few practice blades and most of them have cracked or broken, but that's more likely than not because I am quenching with water. I am in the process of getting an oil quench tank as well but I'm not quite there yet. Also, the steel is a piece of railroad tie, any good for a water quench?

 

elastic-rail-clip-250x250.jpg.546cd3b786343c5fcab7d357d58e9363.jpg One of these if my description was a little vague.

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Railroad clips fall in the dead mid-grade carbon content to the low end of high, so water works alright, but oil is generally better. It's not as hard on the steel. Go buy a few liters of canola oil. And like we had talked about before, free steel is great, but it's always preferable to work with a known alloy if you're making a tool out of it.

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Sounds good! I've got an old 100 lb propane tank that I've cleaned out and a few gallons of old motor oil that I was gonna fill it with for longer stuff. I'll cut the top off it tomorrow and get it set up.

Thanks for the tips!

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Our school used motor oil for quenching, but it very well may be.

And I have heard of many people using motor oil as a quenchant.

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On 6/10/2020 at 7:57 PM, Olorin said:

elastic-rail-clip-250x250.jpg.546cd3b786343c5fcab7d357d58e9363.jpg

One of these if my description was a little vague.

Boy, that's REALLY warped.

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Some of those clips are 5160 and would prefer oil, especially in blade cross sections.  Harder to do a hamon on.

I've yet to see anyone do anything worthwhile blade-wise with a railroad *tie*, the heavy creosote is toxic and the wood isn't that great.

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JHCC, yeah it is rather curvy, but I manage to get it unbent and straight.

 

Thomas powers, what steel would you recommend for doing a Hamon?

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A plain shallow hardening steel, some of the W's are really easy to get good results.  The better you get the more steels you can manage it on.

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On 6/10/2020 at 7:37 PM, Olorin said:

And I have heard of many people using motor oil as a quenchant.

Smoking was once encouraged as a good source of Niacin. Everybody in movies and TV smoked, Granny Clampet smoked Winston, because, "Winston tastes good like a cigarette had aughta."

Frosty The Lucky.

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True, but I am in a well ventilated area (outside) and keep my head back and away from the smoke. I should be fine, and it is easier and cheaper to fill a 100 lb. propane tank with motor oil than Parks 50! Thank you for your concern! :) 

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You can take the chance, but for me and anyone who asks me, I should be fine is never good enough. I would never use anything toxic without proper PPE like in this case a respirator. My brother used to restore old tractors. In the process he worked with toxic materials. He always said working outside with them was safe. He passed away from COPD after about ten years and he never smoked.

End of lecture.

Quote

Chemical Cartridge/Gas Mask Respirator: Gas masks are also known as "air-purifying respirators" because they filter or clean chemical gases out of the air as you breathe. This respirator includes a facepiece or mask, and a cartridge or canister. Straps secure the facepiece to the head. The cartridge may also have a filter to remove particles.

https://www.osha.gov/dts/shib/respiratory_protection_bulletin_2011.html

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Fair enough. I'll invest in a good respirator. Thanks!

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Unless you're talking about used motor oil, 5gl. jugs of peanut or canola deep fryer oil cheaper than new motor oil. Used motor oil is loaded with: finely divided metal particles, hydrocarbon combustion byproducts and antifreeze. 

Inexpensive new motor oil seems to be running about $17.  to  $22. and change per 5 qt. jug. What are you going to need 15-20 jugs?

What can you forge from pandrol clips that's going to need 25gl of quenchant? 

Just because you have that big tank doesn't mean you need to find something to use it for. 

Ah, your "buy a respirator" response just loaded. Haven't priced cartridges rated to protect you from motor oil smoke have you? 

I can't do more than talk sense. Your lungs, your life. Don't bother thanking me again. Please.

Frosty The Lucky.

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OK, I got a larger tank so I could quench potentially larger projects such as swords (if and when I get to that and I actually have a larger short sword in progress that will require a larger tank than what I had previously available), I typically have access to a decent amount of oil so it was more financially feasible to just use that than to buy more, I am aware of the dangerous of toxic chemicals and take precautions in the moment to deal with them (though they aren't perfect they work for what I do). And sorry for thanking you for advice, I tend to be polite to people when talking to them online, but I'll make sure not to thank you anymore.

I will no longer be monitoring this post, I learned what I needed. Çiao!

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Frosty ya cant teach a person that already thinks he has all the answers,  interesting how many people want to make things but refuse to get the proper tools to do it.

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Ah, it's no thing. I just had enough of the snarky thank you. We were young once and knew everything except our #1 tool lacked enough knowledge to apply it to doing useful things. 

One of the working foremen used to say, that when he or his brother would get lippy, his Momma told them, "Talking sense to a fool is like singing to a mule." I'm not calling anybody a fool, kids are kids it's not the same thing. Not really.  

I should learn to quit when the person asking argues with answers they don't like. 

Ahh, sun's coming out, think I'll have a sandwich and make a dump run. DANG! I forgot to submit, ate my sandwich and made the run. A dead freezer is $64 to dispose of and I have to take it apart and separate the pieces! 

I need to go do something else, maybe write waste disposal while I'm still in rant mode.

Frosty The Lucky.

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I bet Steve knows the story about trying to pour tea into a cup already full....

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