introduction and question on 8670

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natesknifepit

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Jul 22, 2020
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new here but ive been making knives for a few years in northwest arknasas. my question comes to those who have made longer blades with 8670 and how it would react to a clayed differential quench and if it would even be worth it with that steel over a through hardening. (dont care about the hamon but the performance) my plan is to make a wakizashi using 8670 and using the clayed differential quench to give it its curve. i have no idea if this would work as ive never done a sword before but i have made quite a few knives with 8670 and absolutely love the steel. i know i would have to pre form the bend before quench if i through hardened it but will it take a curve in the quench clayed if its straight.
 
8670 will make a fine wakizashi .... BUT:
8670 won't work well for a differential quench.
It also won't survive a water/brine quench well.

Solution - Just put the sori in the blade before the quench and do an oil quench.
 
Sweet, that was exactly what i was wondering. Ive got a good amount of experience with it as far as through hardening it for knives but i had no clue what it would do or how it would react for a differential quench or as a sword steel.
 
8670 is so tough that it doesn't need a differential quench to be able to take a 90 degree bend without breaking. Its close to 5x tougher than 1095. I have recently started using it for the knives I used to make in 80CRV2. I like it WAY better than 80CRV2. Its as tough, it doesn't rust quite as fast, the sparks aren't as hot, and its so tough that I can draw a medium sized chopper back to 62 and the edge still hold up to chopping and batonning.

Of course, I got it at Pops Knife Supply. Woot!
 
I’ve got a falchion with a 30” blade out of 3/32 8670 that I just quenched a few days ago, it’s very stable in the quench so even if it did survive a water quench you probably wouldn’t get the drastic curve. It should make a great sword, if you temper down to 58-60 it should be almost indestructible.
 
This is exactly the info i was needing. I knew it was tough stuff as when i first got it in i made a test blade from it and literally beat it with a hammer through 2x4s and pounded the tip over 1/2in into the wood and pried it out. There was zero damage to the blade and it was still shaving sharp when i was done. It tested out right at 60rc so i think ill shoot for just slightly softer than that for a sword and form it to exactly the way i want it and just through harden in oil like i do with my knives. I get just about all my stuff from pops anymore as its a 1 stop shop for everything im needing
 
natesknifepit said:
This is exactly the info i was needing. I knew it was tough stuff as when i first got it in i made a test blade from it and literally beat it with a hammer through 2x4s and pounded the tip over 1/2in into the wood and pried it out. There was zero damage to the blade and it was still shaving sharp when i was done. It tested out right at 60rc so i think ill shoot for just slightly softer than that for a sword and form it to exactly the way i want it and just through harden in oil like i do with my knives. I get just about all my stuff from pops anymore as its a 1 stop shop for everything im needing
Click to expand...

Much appreciated.
 
It’s insanely tough stuff, but I’ve been drawing the spine back with my torch regardless, only on my bigger blades. It definitely won’t hurt, and will make for an un breakable blade!! I use a big pan, with sand, and filled with water.
 
Fiddleback said:
8670 is so tough that it doesn't need a differential quench to be able to take a 90 degree bend without breaking. Its close to 5x tougher than 1095. I have recently started using it for the knives I used to make in 80CRV2. I like it WAY better than 80CRV2. Its as tough, it doesn't rust quite as fast, the sparks aren't as hot, and its so tough that I can draw a medium sized chopper back to 62 and the edge still hold up to chopping and batonning.

Of course, I got it at Pops Knife Supply. Woot!
Click to expand...
I have not been impressed with 80crv2 honestly!!
 
I'm glad 8670 is getting more attention. It is a highly underrated alloy with excellent toughness, which was proven by Larrin's testing.

Here is a repost of a video we made in May 2016. The chef knife was ground from .100" stock and heat treated to HRC 63. The tubing is mild steel:


Here is a link to our inventory. We have a few flat ground pieces listed:
https://www.alphaknifesupply.com/shop/8670-carbon-steel
 
For those of you who use 8670, do you do most of the grinding before or after heat treat?
How is bad is 8670 to warp during heat treat?
 
Tom Lewis Tom Lewis I grind after heat treat but I don’t use any of it thicker than 0.1”. I haven’t noticed bad warp but I almost always put in quench plates while still hot out of the quench so hard for me to say.
 
Tom Lewis said:
For those of you who use 8670, do you do most of the grinding before or after heat treat?
How is bad is 8670 to warp during heat treat?
Click to expand...
I grind after heat treat, worked with 3/32 up to 1/4 and no problem with through hardening. I normally take the blade out of the quench after 5-6 seconds check for warps then clamp in a bench vise to clamp blade straight if need be, it seems to be very stable in the quench. If you leave blades flat before quenching they are very easy to straighten, you can setup plates to put the blade in right after quenching which should prevent any warps that may happen, if that doesn’t work you can do a clamped temper to straighten, if you have a bad warp do a quick temper at a low number like 300-350 for an hour just to reduce stress then clamp your piece to a flat piece of thick steel, I’ve found 1/4-3/8” plates work just fine and you only need one bigger than the blade your working on, temper at your target temp or 25 degrees under for a full cycle with the blade clamped flat, put the warp where the middle clamp flattens it, if that doesn’t fully straighten it do the same thing either at the same temp or 25 degrees higher but counter bending the blade with a penny at the tip and butt of the tang. I’ve never had a blade that couldn’t be straightened following those procedures. No torch marks or snapped blades. And back to 8670 I just quenched a falchion with a 30” blade 7” tang profiled out of 3/32 stock last week that was just pressed between two 2x6 boards that came out perfectly straight.
 
Tom Lewis said:
For those of you who use 8670, do you do most of the grinding before or after heat treat?
How is bad is 8670 to warp during heat treat?
Click to expand...

8670 is less warp prone than 15n20, when using reclaimed 15n20. It’s not bad at all.
 
You have gotten me interested in this steel. In fact, I have just purchased some from Alpha.
What temperature to you temper this steel at? The Alpha chart shows 200 degrees F producing a HRC of 60. Is this right?
 
I don’t have a hardness tester but that can’t be right for a knife. I’m usually tempering in the 325-400 range depending on intended use.
 
Tom Lewis said:
You have gotten me interested in this steel. In fact, I have just purchased some from Alpha.
What temperature to you temper this steel at? The Alpha chart shows 200 degrees F producing a HRC of 60. Is this right?
Click to expand...
That temp isn’t even close to being right for knives and the processes we use, not sure why alpha doesn’t put up an accurate spec sheet, if I remember correctly that’s the spec sheet the supplier provided to alpha but in their own testing they have proven that temp is wrong, I believe they tempered the knife shown in the video above at 200 and it came out to 63. Willie did some great testing that shows around 1525 to be an ideal quench temp to get between 65/64 out of the quench, If your using a oven I’d stick to that temp then play with different temperatures in the temper to see what results you get with your setup. If you don’t have a Rockwell tester dragons breath forge makes some great hardness chisels that let you test your blades to a point, once you have some baseline results with your setup make a few test blades as identical as possible and see how they perform at different hardness ratings. I’ve had good results with most blades at 61-62, if your using a kitchen oven to temper than you have to check what your specific oven runs at because they aren’t all the same.
 
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