Too "thick" of an edge for Heat Treating? (Shallow hardening steel)

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coldsteelburns

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Aug 2, 2010
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Hey guys, I have a question regarding a knife I'm right in the middle of making. I finally was able to get my forge up and running a couple weeks ago for the first time in probably over a year and a half (due to life), and forged out a blade using some of my 1/4" 1075 from Aldo (low Manganese). So I am pretty rusty with my forging skills, as well as my bevel grinding (which I was never that great at anyway) and am attempting to make my first "proper" hidden tang knife.

Anyway, by the time I was finished grinding out all of the forging marks on the ricasso and removing probably more material than necessary in order to make it square and parallel (same thickness on spine side, choil side and just before the plunge cut and tang shoulders on each... or simply all four corners of the ricasso) I am at a thickness of .187" or 3/16". The blade is about 1-3/8" tall at the heel and is about 4-3/8" long to give you an idea of it's size. It's basically a larger (IMO) hunting style knife that is inspired by one of Karl Andersen's typical style hunters.

So the edge of the blade is at about .060" thousandths and I will be clay hardening this blade for a hamon. My lines are scribed .030" apart and I took the edge down to them during the initial ~45 degree grind on the bevels, but I still have just a bit of that first bevel showing on each side cause it to be at .060" just above the edge.

I'm probably being way too technical here for the question I am asking, but what I am wondering is, do guys think I'll be alright keeping the edge thickness where it's at right now while going into heat treating, considering I'm using a shallow hardening steel (with the lower Manganese as well) and will be clay hardening trying to achieve a nice hamon. I DO know that I would probably be grinding away a little bit of the hamon's activity by leaving it thicker than "needed, but I am curious if the blade will have any trouble hardening at least one third the height of the blade.

Like I said, I'm a bit out of practice and want to leave myself a little extra material in case there is a bit of warping after hardening so I can make sure the edge is perfectly centered with the ricasso. I wouldn't be asking this if I was doing a full tang because I'd just take the edge down a bit more, but since this is my first "proper" hidden tang, but I want to be able to do any correcting post HT if needed without needing to take down any more of the ricasso (spine) thickness if the edge needs to be re-centered due to possible warping etc.

Sorry for the long post, I just like to be thorough ;) . Thanks

~Paul
My YT Channel Lsubslimed
... (It's been a few years since my last upload)
 
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It should be fine as is. You *might* lose a little bit of fine activity but it will probably be pretty negligible.

I take my edges down to about .030"

Matt Gregory and I just recently did a test on Aldo's new batch of 1075 where we took the edge down to almost nothing, I think it was like .005" or something like that, and quenched it in parks 50. There was no warping or cracking or distortion of any kind. There was also no overheating either.
 
I leave my edges on carbon steels at 0.050" prior to heat treat. This allows me to thermal cycle and heat treat and not worry about decarb thickness. I've had decarb up to 0.010" per side, but that's the high end. I know I have clean steel once I get down to 0.030".
 
J. Doyle said:
It should be fine as is. You *might* lose a little bit of fine activity but it will probably be pretty negligible.

I take my edges down to about .030"

Matt Gregory and I just recently did a test on Aldo's new batch of 1075 where we took the edge down to almost nothing, I think it was like .005" or something like that, and quenched it in parks 50. There was no warping or cracking or distortion of any kind. There was also no overheating either.
Click to expand...

I noticed this too with my recent 1075. It doesn't warp at all. I have some 1084 that will come out like a pigs tail if your grind it too thin but this 1075 is awesome. I thought maybe it was luck, nice to hear others experience the same thing.
 
Awesome, that's encouraging to know. This 1075 is actually from a few years ago and this is also my first knife (well, it's the 2nd but the first was a lost cause) using it. I'm not sure if my 1075 is any different from Aldo's recent batch, but I'm not worried as you said it should harden just fine at this thickness.

John, I'm curious to hear what your HT procedure is (time & temps) for your 1075 knives, which always come so dang perfect looking (and performing I'm sure) btw.

Also, would you suggest that I do my normalizing and thermal cycling first, then clean up the blade, then apply the "clay" and harden the blade?

Or, should I put the clay on, do my normalizing, thermal cycling and hardening all at the same time? When I clay my blades I do apply a thin wash of clay to the entire blade before applying the clay to the spine, so I'm not sure if that will be enough to prevent the scale/decarb from affecting the quench and thus the hamon.

I'm kinda thinking of doing the former, because if the blade happens to warp a bit during one of the thermal cycles I'd obvious like to correct it before quench, and I won't be able to do that (or possibly even see a very slight warp) with the clay on, or without causing the clay to fall off while trying to adjust it.

Thanks for the help guys. :)

~Paul
My YT Channel Lsubslimed
... (It's been a few years since my last upload)
 
I know you asked John but I've been having good results normalizing and thermal cycling first, then doing clay and quench. I'm austentizing at 1475f and while I haven't checked the RC of any yet, every one has skated file after going through a bit of decarb. I didn't see anything different between the one blade I gave a light wash coat of and the next 4 i did not. I quench in parks 50.

I had one small blade fail to produce a hamon and i don't know why, the only thing different about that one was the size. Almost like it cooled too fast clay or not.
 
I do all my thermal cycling first, then apply the clay and heat and quench.

I'd ditch the thin wash of clay on the whole blade and just do the clay for the actual hamon.
 
Alright cool, 1475 F does seem to be pretty much the go to austenitizing temp for shallow hardening steels. I'll just do the typical 4 step normalize & grain refinement cycles with some of my PBC anti scale, or maybe even just a thin wash of satinite to keep clean up for applying the clay to a minimum. I have Parks 50 so quench speed won't be a problem.

I guess I won't be using the thin wash of clay since both of you guys seem to be on the same page about that. I've always just just added the wash as one of those extra steps that "might help but shouldn't hurt", since it can help speed up and even out the quench as I've read in the past that it helps with collapsing the vapor jacket. Although it may not be an issue anyway with what I'm using.

I swear I've done all of this before, it's just been so long that I need to be refreshed on certain things lol.

Much appreciated fellas! :thumbup:

~Paul
My YT Channel Lsubslimed
... (It's been a few years since my last upload)
 
1475F is the go to temp for hyper-eutectoid steels, whether they are deep or shallow hardening. The reason being you bring just enough carbon in solution to reach that maximum RC hardness post quench (~.77%). The rest of the carbon is left over as carbides for wear resistance. The more carbon you put into solution above that point, the more plate martensite you get (more matrix strain), the more retained austenite there is, the lower the HRC number becomes, and the more carbon you rob from the carbides. Whether it's W2 or 52100 or O1, 1475F is the sweet spot. And depending on the actual alloy, your kiln, your thermocouple, the moon phase, etc (ok maybe not the moon phase), that target temp may vary a little. eg. 1460 for W2, 1490 for O7. You get the picture.
 
samuraistuart said:
1475F is the go to temp for hyper-eutectoid steels, whether they are deep or shallow hardening. The reason being you bring just enough carbon in solution to reach that maximum RC hardness post quench (~.77%). The rest of the carbon is left over as carbides for wear resistance. The more carbon you put into solution above that point, the more plate martensite you get (more matrix strain), the more retained austenite there is, the lower the HRC number becomes, and the more carbon you rob from the carbides. Whether it's W2 or 52100 or O1, 1475F is the sweet spot. And depending on the actual alloy, your kiln, your thermocouple, the moon phase, etc (ok maybe not the moon phase), that target temp may vary a little. eg. 1460 for W2, 1490 for O7. You get the picture.
Click to expand...


Thanks for adding that, Stuart, it's always good to know why we do things as opposed to just whether or not they work. I just recently start reading through "Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel" by Verhoeven etc. again. I made my way through a few sections in the past but this stuff needs to be saturated in your head in order for one to put it altogether and understand and apply it... at least for me it does. I never took any chemistry classes in school so there aren't really any of those connections made, such as with there being a eutectic point in phase diagrams other than steel.. lol :foot: .. which I'm sure I would've learned in any beginner chemistry course. Of course there are some 'ah hah!' moments simply from the tons of unorganized info I've picked up over the years of reading on the various forums etc. :cool: :thumbup:

~Paul
My YT Channel Lsubslimed
... (It's been a few years since my last upload)
 
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