Simple Heat Treat Steels

E

ErikD

Joined
Dec 5, 2000
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I am just getting started in making my own knives. Hopefully soone I will be able to order some steel and start grinding out some blades. I know that O1 and 440C are pretty much the standard steels to start with. At the moment i am leaning towards O1, so hopefully I can do the HT myself and save some money. Being a student I don't really have all that much money to spare. Another thing I like about O1 is that it is a good deal cheaper than 440C, and just strting I am sure I will make mistakes and ruin blades. I would much rather waste a piece of steel that cost me a few cents a foot than a few dollars a foot.

My question is on what I can use to get the O1 up to the correct temperature to harden. I have an old BBQ grill, but doubt that would do the trick unless I rig up some kind of blower. Would one of those MAPP torches do the trick? I have a propane torch, and an Oxy/MAPP torch. The propane alone won't get it hot enough, I know that. With the Oxy/MAPP rig the heat is concentrated in such a small area (meant for welding), that I doubt I could heat the whole blade enough. Another option I might have is using my home furnace, as I can open it up and stick the blade in there. Only problem with that is I don't really think oil quenching in my basement is the best idea.;) I would also need to work whenever the burner decides to come on, and hope it stays on long enough to get the steel where I need it. I am guessing that a MAPP torch might be my best bet. Or if that wouldn't work then maybe building a cheap forge, are there plans in Goddard's $50 Knife shop? Been meaning to pick up that book for a while now. Thanks for your help.
 
Use O1. 440C requires much more care in heat treatment, at much higher temperatures. :eek:
 
On the contrary,i use a small propane torch in the one brick forge and it heats up the 01 plenty hot. All you need is critical temp,and to make sure your oil is preheated a bit..I have had great luck with 01 and would definitely recommend it to someone just starting[like me]. hope this helps.
 
propane can be used, it just might take a bit of time.
Look up the one-brick forge (in wayne goddard's $50 knife shop book). A couple of fire bricks, a propane torch. Get a magnet to test with and have your quenchant close at hand.
 
I didn't doubt propane would get it hot enough if used in the forge. I was wondering more just using the torch to heat the blade in open air. Looks like I will have to get myself the book and build a one brick forge.:D
 
I've used mapp in open air. If you make a 1 brick or can forge, though, you will save alot of time.

Tim
 
I guess I will have to make a small forge. At this point though I think a small can forge might be the easier and/or cheaper option. I am thinking something like a can lined with some kind of heat resistant cement and a hole drilled in the side to let the flame in. I had some furnace cement just lying around in the shop, and an empty soup can, so I gave it a shot. It will be to small to do any blades, but just testing out the idea.

Anyway, for when I do build a forge to use for HT I do have a couple of questions. If I do go with a can forge, do I need to close the top off, from my quick searching it seems as if leaving it open would work out. Also, would it be ok if I can only fit the blade into the forge? Since I am going to be using O1 I could do a differential HT, leaving the tang soft as it would never get to critical temp, correct? I would guess though that this might make it take a bit longer to get the blade up to temperature due to heat loss through the tang, but I could live with that. Thanks again.

The thing that has me leaning more toward the can forge is having to drill a hole in the brick. I can't really think of a good way to drill a hole thorugh a 9" piece of brick without buying expensive drill bits. Also this would limit me to making blades that are not any wider than 1" at any point, so a soup can seems a bit more versitle. Plus, if my idea works it will be a freebie:D :cool: .

Just one more question. Does it matter if the flame coming out of the torch hits the blade? Or would I need to get it setup so that the flame just hits the center or opposite side of the can?:confused:
 
If you are building a small forge from a large can of some kind, no the flame doesn't have to touch the blade, the flame will be heating the interior of the can.

To start though it is perfectly doable to heat treat small blades (knives with blades up to 4" or so) with propane torches only, if you build a small enclosure of four or five regular firebricks just to help concentrate the heat of the torches. I used two hand held propane torches with jumbo flame tips and some fire bricks to heat treat my first knives with good success. I rigged the blades so that they were inside the stack of bricks edge up so that I could then play the torch flames alog both sides of the blade simultaneously to get a more even heat. If done in low light conditions this method is surprisingly quick and controllable as it is easy to see when the blades goes through the phase change as it passes through the recalescense point.

Any kind of forge though gives you better control as long as you don't have any severe hot spots. Always beware of overheating the tip, the most sensitive and vulnerable point when heating a blade
 
Don't use a torch in open air. It is important to heat the blade uniformly. Have your quenching oil and your tempering oven preheated. Preheat the quench to about 135 F. and the tempering oven to 400 F. When the magnet no longer attracts the O1 quench and place in the tempering oven before the O1 falls below 125 F (hand warm). Temper 1 hour. Cool to room temperature and temper again but this time at 375 F for 1 hour (about 25 degrees less than the primary temper).

You will like O1 as a steel to work with and as a great knife blade. Later when you are tooled up to heat treat 440C you will probably not want to because then you will be able to heat treat steels even more actractive to you.

RL
 
I just tried out my "forge" made of a soup can and some furnace cement. I took a small soup can lined it with some furnace cement and drilled a 1/2" hole in the side. This was just mean as a test to see if the cement would work to get steel hot enough. Well I took my MAPP torch and pointed it in the hole, but about an inch away from it. I was not able to get the steel hot enough, at least I don't think I got it hot enough. I can think of a few possible problems:

1. I was using a scrap of mild steel, as I don't have any O1 yet
2. The cement didn't dry 100% yet
3. The cement just doesn't work all that well to hold the heat in the can
4. I didn't have the torch pointed in just right
5. The cement was bad, I had it just lying around and it was partially hardened before I used it

I am thinking it is probably either 1 or 3. Even if the torch wasn't pointed just right it I think it should have got things hot enough as I left it for 10 - 20 minutes. The outside of the can did get hot, but that may just have been from the flame hitting the side of the can some. Any thoughts?

I will probably just end up buying some Inswool or Kaowool and satanite to make the one I will use for HT blades. I don't think I would have enough cement left for a larger forge anyway, and these supplies aren't that much more than the cement.
 
My juice can forge mixed furnace cement with vermiculite (1-3or4 mix)(some say pearlite is better) I packed it around the gas bottle for about a 1 inch wall then pulled the bottle out. I have some more furnace cement painted on in a weak solution to even the mixed stuff, and the inside painted with ITC 100, which reflects in about 98% heat so the story goes. I'haven't fired it up yet, I'm protesting the negative 10 degree temps in the shop. I plant to use a brick or two across the mouth of the can, to hold back the heat a little. Mine is set up for two torches.

>Well I took my MAPP torch and pointed it in the hole, but about an inch away from it.

The pictures I am working from show the end of the nozzle even witht he outside of the can, almost sealing the hole. The gas flies in, creating positive gas pressure, which holds back the flame enough that the nozzle is never overheated, nor is the ouside of the can (assuming sufficient insulation)

>The thing that has me leaning more toward the can forge is having to drill a hole in the brick. I can't really think of a good way to drill a hole thorugh a 9" piece of brick without buying expensive drill bits.

Are you talking about a firebrick, or a refractory brick (i hope those are correct terms)? The refractory bricks, that cost about 8 Canadian each are pretty soft. I have just the one, and haven't tried it yet, however it looks easily drilled, virtualy with a spoon. The fireplace bricks, which are also a light sand colour are hard, and you would need something like a watercooled diamond saw to cut one, it wouldn't be easy, but then they aren't the bricks one uses for the one brick forge.
 
Well I guess it is worth giving another shot with the nozel even with the outside of the can, won't cost me anything. Just from what I had been reading it seemed as if the nozzle should be a bit out of the forge, but I might have misunderstood.

Yeah, I know that the correct firebrick is soft and should be fairly easy to drill. I just meant that I don't have a 1" or larger drill bit, and that they are rather expensive. A can forge just seemed easier and cheaper as a first attempt.

What is the purpose of the perlite or vermiculite??:confused: I used to use the stuff when I was doing landscaping, but wouldn't think it to be very heat resistant seemed kinda like foam particles. Anyway the stuff is cheap enough, I could buy a bag and make another mini forge for experimental purposes.
 
If you look around the various sites that talk about homemade refractory cement, there are oodles of formulas. These two materials tend to be the components used to insulate the cement. There are more or less complex formulas, but enough people were having luck with just stove cement and V or P that I decided to go that way first. You have to give it a long time to dry, or at least with the V. As you say they are very light, so when you mix 3-4 parts of P/V with the stove cement (some add a little portland), you end upwith a kind of cement foam.

On a lot of the bigger propane forges, the fit is designed so the tip of the nozzle is flush with the outside metal shell. There is usualy an inch or two of insulation also.

I have seen some of the torch style actualy rest the nozzle against the can, just so there is something holding it there, some of the forges have little or no internal insulation (and therefore hardly last longer than a use or two). In this kind of deal the nozzle is inside the can a fraction. I haven't seen any can forges with the nozzle outside, but as long as the gas is all getting inside, and all burning inside, and the same hole you are shooting the gas through isn't the hot gas chimney, I don't seem much of a problem.

The one brick forges do have the torch sorta outside the forge.

I am not sure everyone is drilling the holes full size in the bricks. I thihnk they are drilling holes and enlarging them with various tools like hacksaw blades.
 
Those are some cool forges, but big by some standards.

Is that a ventury burner in the last photo, and what is the satelite dish thing on top for?

That's where I store my gas can just in case it's a slow day!
 
Not a satellite dish, but for air control and the red container has Heatbath quenching oil. That burner is a full size venturri with a 1" tube. Takes just 8# of pressure to get to yellow heat and it will hold it at 2#.


Ken Beatty
 
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