Heat treating knife rack?

T

Theforerunner

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Jul 11, 2018
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Up until now, I’ve been using a home made gas forge for heat treating high carbon steels but someone awesome just sent me a paragon pkm9d and I want to start playing with 440c, but it only came with one ceramic knife rack that only has two little rods on it.

Is there something I can make myself to use as a rack to hold multiple blades at once for heat treating?

Edit; also, is there a specific type of foil I should be looking for for wrapping or is it just stainless steel foil? And from what I read, putting a piece of paper or wood in the foil is a bad idea, but the manual for the paragon itself says to put a small piece of wood in there so I’m confused I guess about that.

Thanks
 
When i received my firebricks for my oven, one was broken. I cut a slab 1/2" thick and flat sanded it smooth on the cut side. Then i took a handsaw and made some slits on sawn face deep enough to hold my blades upright. I make small folder blades, keep in mind. I just set the spine of a blade in one of the slits.

I think cermaic racks are pretty cheap though.
 
I think I’ll try this too. I’m gonna be with ig with smaller 1/8” thick blades so it shouldn’t be too difficult to do. I just wonder what kind of rod they use on those things. Nichrome? Almost like... welding rods?! Why does that sound insane to me?
 
I use the soft fire bricks too. The bricks are so soft it is easy to just use the knife to scrape the grooves in.
 
Soft brick, cut into 1" thick slabs works decently well. Hard brick is better and cheaper in the long run (though a pain to machine). You could probably use HSS or something too.

309 and 321 are the alloys I am aware of for stainless "Tool Wrap" think 321 is the cheaper one that is good to 2000F. 309 I think is good to 2200F. But I don't remember off the top of my head. Be careful when using, that stuff is nasty and can cut the crap out of you.
 
Thanks for the advice. I’ll use it moving forward. Been a long time lurker of the forum and grateful for the useful information I’ve found here.

Tom
 
I have bent racks up from 3/32" stainless welding rod. They are not pretty and are not permanent, but they get the job done.

If you cut stainless welding rods with a normal pair of engineers pliers that leave a slight V-shaped cut end, you can chuck it in a drill and drill it into a piece of Insulating Fire Brick (the soft stuff). If you drill it in and then cut it off an inch or two above the brick, you can make a pretty effective rack. The stainless will Oxidize when it gets hot and the Oxide layer will spall off as it cools. 316 tends to lose a layer each time it cycles through about 850 degC, 1562 degF. 309 will retain the Oxide layer until it cycles through around 1000 degC, 1832 degF and 310 will handle about 1100 degC, 2012 degF. 316 seems ok for the temperatures used for many Carbon steels and 310 will handle the temperatures used for many stainless steels pretty much indefinitely.

You can just cut pins from welding rod and push them into IFB, but using the drill dramatically reduces the likelihood of cracking the IFB.
 
timgunn1962 said:
I have bent racks up from 3/32" stainless welding rod. They are not pretty and are not permanent, but they get the job done.

If you cut stainless welding rods with a normal pair of engineers pliers that leave a slight V-shaped cut end, you can chuck it in a drill and drill it into a piece of Insulating Fire Brick (the soft stuff). If you drill it in and then cut it off an inch or two above the brick, you can make a pretty effective rack. The stainless will Oxidize when it gets hot and the Oxide layer will spall off as it cools. 316 tends to lose a layer each time it cycles through about 850 degC, 1562 degF. 309 will retain the Oxide layer until it cycles through around 1000 degC, 1832 degF and 310 will handle about 1100 degC, 2012 degF. 316 seems ok for the temperatures used for many Carbon steels and 310 will handle the temperatures used for many stainless steels pretty much indefinitely.

You can just cut pins from welding rod and push them into IFB, but using the drill dramatically reduces the likelihood of cracking the IFB.
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Thanks! thats a good idea. I wondered if welding rod would survive the heat of 1850F or what the ones in bought stands were made from.

as far as the 310 stainless foil, are you suggesting that it could be re-used for multiple firings? or just that it can stand up to multiple heats for fancy alloys?

tom
 
Sorry, I was unclear: I meant the welding rod used for the rack. 316 is easy to find. 309 is not difficult. 310 is less common. I have not tried 312, but it is a fairly common rod for dissimilar metals and may hold up to stainless HT temperatures.

I have only ever used the lower temperature-rated foil and then only a few times. It certainly didn't give the impression of being reusable.
 
timgunn1962 said:
Sorry, I was unclear: I meant the welding rod used for the rack. 316 is easy to find. 309 is not difficult. 310 is less common. I have not tried 312, but it is a fairly common rod for dissimilar metals and may hold up to stainless HT temperatures.

I have only ever used the lower temperature-rated foil and then only a few times. It certainly didn't give the impression of being reusable.
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Oh okay got you. I didn’t think you were talking about the rods, makes a lot of sense now. Thanks
 
I use stainless steel angle iron and cut notches into it and lay the blades in that. But I don’t use foil for my high temp stuff so this works great.
 
JTknives said:
I use stainless steel angle iron and cut notches into it and lay the blades in that. But I don’t use foil for my high temp stuff so this works great.
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How does that work exactly? Do you quench in oil? Or air quench? Most of the knives I make I use the blackening from quenching to my advantage. Im under the impression that when you heat treat the stainless it not only oxidizes/produces scale, but it like, actually loses carbon? Effectively making the blade less strong or whatever? Or is it just the same as heat treating carbon steel because if so I would just forego the entire foil situation.
 
Theforerunner said:
How does that work exactly? Do you quench in oil? Or air quench? Most of the knives I make I use the blackening from quenching to my advantage. Im under the impression that when you heat treat the stainless it not only oxidizes/produces scale, but it like, actually loses carbon? Effectively making the blade less strong or whatever? Or is it just the same as heat treating carbon steel because if so I would just forego the entire foil situation.
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When you austenitize steel at the temperatures required for stainless, an oxidizing atmosphere does a lot of bad things to it, especially when many of these steels require long soaks at temperature. simple HCS also will suffer similar problems, but it is held at lower temps for shorter soaks, so the damage is generally constrained to the part you are going to grind off anyway.

I think JT uses a nitrogen or argon purge for his high temp heat treating (cause it is way cheaper and and has a bunch of advantages over SS foil if you do lots of that type of work). Speaking of, JT, what CFH do you end up running. I have a bunch of argon lying around, it may be easier for me to toss an extra tank and regulator behind my oven after I run out of my foil (which may take a while what with the fact that almost everything I do is forged and almost never SS).
 
joedhiggins said:
When you austenitize steel at the temperatures required for stainless, an oxidizing atmosphere does a lot of bad things to it, especially when many of these steels require long soaks at temperature. simple HCS also will suffer similar problems, but it is held at lower temps for shorter soaks, so the damage is generally constrained to the part you are going to grind off anyway.

I think JT uses a nitrogen or argon purge for his high temp heat treating (cause it is way cheaper and and has a bunch of advantages over SS foil if you do lots of that type of work). Speaking of, JT, what CFH do you end up running. I have a bunch of argon lying around, it may be easier for me to toss an extra tank and regulator behind my oven after I run out of my foil (which may take a while what with the fact that almost everything I do is forged and almost never SS).
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Yeahhhh I figured I’d need some foil. Where’s generally the best place online to get a hold of some? I think Texasknifemaker has 2’x4’ rolls for 35$. It seems like to even get anywhere close to a value here I’m going to have to buy 100$ of it at a time. I’ve only bought steel and g10 from alpha knife supply before, nothing from Texas.

And while we’re on the topic of procurement, looks like I can get two slabs of aluminum for plate quenching from amazon for 20$ a piece (1.5” x 6 x 12)

Is there a better place to find this that anyone knows of?

Edit: I also thought it might be a good idea to throw out that I’m working with some 440c currently if I haven’t mentioned that before
 
I think the last time I bought tool wrap (my 2nd roll), I got 100' of it of amazon. I only use it for HSS or stainless, and I don't do either very often as I generally buy prehard HSS and forge most all my knives. My first roll at 50' lasted a couple of years.

I am sure you can get the aluminum cheaper from a scrap bin at the local metal supplier (if they have any in stock), but for $40 I may just grab it off of amazon.
 
As far as the blade racks are concerned ceramic works best from my understanding. If you were in a pinch I wonder if it would work to use a few of those Dixie cup sized flower pots? You could stand the blades up on their spines in between a couple of them I would think. I wouldn’t use any kind of metal as it’s heating up so high, for long periods of time. Relatively speaking that is.

If you end up buying some stainless steel foil you might see if the same site sells ceramic heat treating racks too. About a year or two, when I got my Evenheat oven, I got both the stainless steel foil and a ceramic knife rack with rods, from USA Knifemaker. I don’t think the knife rack was very expensive either. One thing you might also consider is that a metal rack might adversely effect your heat treat. For instance, if you put it in with the blades at the same time, I could see it acting as a heat sink and pull heat from the blade where it was in contact. Not sure if this would happen. Just thinking out loud.

I would say, if you’re going to go to the trouble of heat treating stainless in house, it’s best to do it right and get a decent ceramic rack. There’s so many little things that can go wrong with heat treating complex, high alloyed steels, it’s best to remove any variables you can. $30 really isn’t that much for a purpose built ceramic blade rack. That being said, you might be able to make your own by drilling into a fire brick and putting rods in the holes. I’m just not sure where you’d get ceramic rods.

Good luck
 
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I made racks out of 1.5" angle iron. I just cut slits in one side wide enough for my blades. They are oxidizing and getting smaller and smaller with each run. But I've done i would guess 20 runs with them and they are still going strong.
 
Come to think of it, you might be able to make your own rack by drilling into a fire brick and putting rods in the holes. I’m just not sure where you’d get ceramic rods. Not sure which type of fire brick would be the easiest to drill into without cracking or breaking. Soft maybe... I would think a hard fire brick would last longer though. It wouldn’t insulate or absorb/retain heat as well as a soft fire brick, but it would work better in the long run I bet.
 
I think I’m going to start with trying to just make new rods out of stainless rod for the one ceramic homer I have already. I don’t see why I would need two holders for something shorter than 7.5 inches or so. I just think it would be harder to try and weave multiple blades through both of them, and remove them when they are ready to quench.
 
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