Heat treating without big investment

A

Absinthe

Well-Known Member
Forgive the n00b but I originally posted this in the wrong area, so I am cross-posting it here via cut and paste.


I am considering doing my own heat treating, 1 because I am cheap, and 2 because as part of the process I want to have my hands in it, at least once. When I was in school a million years ago, we all made cold chisels. To HT them, we got them super hot then dunked them. When we were done we polished them up and hit them with a torch until we could see straw color near the working edge, then left them on top of the forge and picked them up the next day when they were cold. That is all of my first hand knowledge of the HT process.

I am going to work with the easiest steels I can for some time such as 80CRV2 and perhaps some 1084 and maybe some O1 or W1 if I can find it. I am assuming that I can get to 1500° with just a torch, and I think I can use my toaster oven to get to 400°-500°.

Is there anything I am missing? Or do I need to make a 1 brick or 2 brick forge?

Is it worthwhile to pick up a set of Rockwell files, or can I just trust the process and expect specific results?
 
I'll start with the Rockwell files. I found them hard to use in that I could never get a real feeling of the hardness in my blades. Others may have better luck and some pointers.

As for heating with a torch I feel you can't get a nice consistent and even heat. I would build some type of small brick forge that you can funnel the torch heat into.

I had a very small forge, and I treated a few 1080 and 1095 blades with some success. However, I'm the type that likes the best and I throw money at it if I can. I bought a Paragon Oven and a used true Rockwell tester.
 
CDHumiston said:
I'll start with the Rockwell files. I found them hard to use in that I could never get a real feeling of the hardness in my blades. Others may have better luck and some pointers.

As for heating with a torch I feel you can't get a nice consistent and even heat. I would build some type of small brick forge that you can funnel the torch heat into.

I had a very small forge, and I treated a few 1080 and 1095 blades with some success. However, I'm the type that likes the best and I throw money at it if I can. I bought a Paragon Oven and a used true Rockwell tester.
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Thanks, seems like what I was expecting. I will keep an eye out for insulation fire bricks or refractory cement. I figure I can do either the 1 brick or coffee can... Do they still have coffee cans? :) At some point I want a small ceramic kiln, I wonder if there is any crossover in functionality to look for.
 
The Mr Volcano Hero forge on Amazon is less than 100 bucks. There's a larger one for less than 150. These forges get great reviews. I don't think you can make a forge for less than that unless you're sticking a butane torch inside of a couple of fire bricks.
 
The torch and fire brick, or coffee can and refractory was my plan. I am not interested in being a blacksmith, nor do I really care to make large blades. (Mostly interested in folders and the ilk by stock removal). But I did see the Mr Volcano and I have considered it.
 
The problem with a two fire brick forge with a hand torch is that you will quickly end up with a bunch of empty tanks to deal with. That's why I recommended a scaled down asperated burner run off a 35 propane tank. If you can find a small blower you might even be able to cobble together a blown burner from parts that you can get from a hardware store or at least High Temperature Tools and Refractory.

Doug
 
Doug Lester said:
The problem with a two fire brick forge with a hand torch is that you will quickly end up with a bunch of empty tanks to deal with. That's why I recommended a scaled down asperated burner run off a 35 propane tank. If you can find a small blower you might even be able to cobble together a blown burner from parts that you can get from a hardware store or at least High Temperature Tools and Refractory.

Doug
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What I do have on hand is a big propane tank. Like 1/3 larger than you would have on a BBQ grill. I also have a set of hoses and a torch that was intended to work with it along with an O2 tank for Oxy-Fuel rig. I bought the tank, hoses, and torch from a widow but left her with the O2 tank because it was clearly marked "Property of ..." and the name of the local rental company for such things. And it has a proper regulator as well. So I have a good starting point for whatever I end up doing.

My fear with too much investment is that i will eventually settle on some HT service and want simply to send stuff out. Or I would want such controls over my process that I would want to invest in a kiln or proper HT oven. I wouldn't mind having a fire brick left over, but having a full on forge of whatever kind would feel wasteful.

I am not counting anything out yet, just trying to come up with a plan.
 
If you go with the two brick setup, take your bandsaw and cut the torch head off the valve. Get a bbq grill regulator and hose, and cut the end of the hose off. Then you can slide the brass torch head into the hose, secure it with hose clamps, and run it off of 20lb grill tanks. A tank will last for a long time, and then you don’t have to keep buying the little hand tanks. It’s easy and cheap.
 
How does one effectively manage a heat treat with this kind of setup? Either 1/2 brick or torch. When I look up specific steel specs, it will say something like xxxx degrees, soak 5 minutes, quench (in one medium or another). Then temper at xxx degrees for 2 hours. Usually giving different temperatures for different rockwell scores.

The usual tutorial will speak of a magnet and the piece losing its attraction to the magnet. However, does that mean it has reached the austenitizing point that it would after obtaining said temperature and soaking? Or does that mean it has just reached the temperature, and now needs to be soaked for 5 minutes?

Again, my whole real world experience in this was making a cold chisel in HS. We forged that out of octagonal steel so it was not too many blows of the hammer to shape it :) But, they said stick it in the forge until it is orange to bright red, then pull it out and quench it in the bucket. I swear there was water in it, but that was a long time ago. Then we shined it up with steel wool, and heated the base of the chisel until we saw "straw" color at the edge. Then "congratulations, you made a thing!" I kind of wish I still had that, I'd love to see if it worked as well as I remember.

But no tutorial or video on HT knives makes it look this simple. So I assume there is either something I am missing, or everyone is out there sending Paragon $2K to get started, and Mr Volcano be d@^&ed :)
 
You are asking a lot if really good questions which gives a good insight of where you are in your knife making journey. We have all been there and many/most have asked similar questions. Suggestion, spend a few "hours" searching this forum for your questions, there is a huge wealth of information from earlier postings.
Regarding heat treating - its really complicated even for the experts, and lots of conflicting opinions. Read Knife Engineering by Larrin Thomas, he's one of the experts on metallurgy.
 
MTBob said:
You are asking a lot if really good questions which gives a good insight of where you are in your knife making journey. We have all been there and many/most have asked similar questions. Suggestion, spend a few "hours" searching this forum for your questions, there is a huge wealth of information from earlier postings.
Regarding heat treating - its really complicated even for the experts, and lots of conflicting opinions. Read Knife Engineering by Larrin Thomas, he's one of the experts on metallurgy.
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That book is on my short list. But in the mean time...

I get that it is not a "toss your hands in the air" process. But I am aware there are people out there that are doing this without a proper HT oven. They are limiting themselves to very forgiving metals, which they tend to list 80crv2, 1084, 1080, 1075 and so forth. (Obviously not SS or CPM) So is it an issue that these metals are so forgiving that even if they don't get it quite right, it is still okay? Perhaps who cares if it gets quenched to exactly 69RW or tempered to exactly 62RW and they are just happy with 54RW or whatever they get? If the file skates then they are happy, and if not try again for a hotter color? Or is there some process they are doing with a magnet or a ir laser thermometer or just SWAG and prayer?

I do get that a programmable heat source with good sensors/probes and timers and such can pretty much do everything but quench. But what are the folks actually doing that haven't invested in these devices?
 
Honestly, most of them are doing it wrong. I say that from experience.

Forge heat treating can be done. But you really need a much, much better understanding of basic heat treating than any beginner has.
 
My first knives were done in a small Atlas forge. They were 1084 and 1080. I bought a thermal sensor and tried to regulate the forge as best as I could. I heated the steel to non-magnetic and tried to stabilize the forge at 1500F the best I could. I soaked for the required time and then plunged into Canola oil.

I got some good results, and I got some bad results. I was making a lot of coupons to break and look at grain structure. I got pretty good at getting a nice heat treat in this manner, but I was never satisfied. I was also looking at working more with stainless steels...so a Paragon oven became a must buy for me.

Other than my grinder, the oven is the best investment I've made so far. But as I said in an earlier post, I don't mind throwing some money at a hobby that I enjoy this much. Nothing makes me feel much better than making a knife I'm proud of...
 
@Absinthe If you are only going to be doing folders and springs, an alternative furnace source may be something like a dental or jeweler's kiln. The chambers are small, they're usually all manual, and you have to be VERY SURE about the max temp before purchasing. Craigslist type thing. Set up a search bot like @MTBob mentioned the other day and let it creep.
 
Salt melts at around 1475, non magnetic is a bit cooler, so if you go only to non magnetic, some steels may not harden properly. Salt melting on a blade is a pretty good indicator that it is very close to 1500! I picked up a thermocouple so I can put that in the forge to see how hot the forge is when I do simple steels; I am hoping to be able to help keep the heat down to where I am looking for to let is soak without going way hotter. A muffle in the forge helps, too (large tube of steel) to help even out the heat.

I get doing your own HT, but I would stick to simple steels for now or get the small kiln. I usually send my high end steels off for heat treating, especially the SS and CPM stuff and bring high carbon to a local knife forge place where I can use their ovens and quench tanks. Higher temps, longer soak time, needing cryo, etc means more equipment and better equipment. I can send 23 blades off for HT and it's around $210 shipped back and forth, so it's like $10 a blade and they are professionally done. Eventually, once my forge is up and running, I will do the simple carbons myself (80CRV2, 1080, etc), but will still bring the 52100 and stuff to the forge to have it done better with them watching until I am confident in the process.
 
If you get a thermocouple and stick it in your forge, you can control your temp as good as anything else - for carbon steels anyway. I used to use my NC whisper lowboy. Had a thermocouple stuck in it, I think that was about $400. I would get the whole thing good and evenly heated up to about 1800 or so, then pull the NC burners out and stick in two regular old torches like you get at the hardware store into the burner holes in the top. Those torches would allow you to turn down the heat to 1500, and once you got them set, you could maintain 1500 +|- 10 degrees or so all day long. You have to use a baffle though. The direct heat from the burners will make hot spots. If you are good with wiring and piping and stuff like that, I’m sure you could rig up a small salt tank with a automatic gas valve and such. I’m not, I just bought a HT furnace :)
 
If you're going to use a propane torch, use as big and "soft" of a flame as you can get.

Tempil sticks are a good way to judge the surface temperature of something without needing a thermometer. I think Markal makes them up to 2500F. They aren't cheap (not as cheap as Crayola, anyway), but they aught to last you a long time.

I've been thinking about building my own (very large) heat treat oven for some time now. Maybe 3X2X2 feet. Maybe a bit bigger. Something I could could fit an anvil in for pre and post heat when I weld them up.

Anyway, obviously it has to be a big insulated box. The tricky bit is getting even, controlled heat. I'm going to heat it with propane burners controlled by a kiln controller. Instead of the controller powering heating coils, it'll control the blower and propane valve solenoids. I'm fairly certain I'm going to build it into a hillside by my shop.

Sent from my Champion Forge using Tapatalk
 
It's funny you mentioned the cold chisel and quenching it in water.

I forged a cold chisel 2 days ago and quenched it in water. I didn't temper it, though. I need it for some really hard material and I'm going to reforge it into a knife when I'm done with it.

Sent from my Champion Forge using Tapatalk
 
Radiaton and Oxidation Colors of Steel.jpg
Here's a pretty useful chart if you want to heat treat steel "old school". This is how I heat treat. Maybe I'm just lazy? I get good results. Good enough for me and my use, anyway. This is after a LOT of trial and error... lots of error. Cracked knives and such. The lessons really stick when you have to throw away a a knife after a full day of forging.

Edit: it does depend on your lighting, but if you have consistent lighting (not GOOD lighting, just consistant) you get fairly good at judging temperature. Goes dark, a little red, a little bit more red, orange, yellow, really bight yellow, then a shower of sparkles. Avoid the sparkle showers. They sound like lots of fun and yes, they DO look cool, but when you grab the tang of your knife to pull it out of the forge and all you have is 3/4" of blade left, the sparkles loose their appeal.

In summary: Sparkle showers are to be avoided.
 
52 Ford said:
If you're going to use a propane torch, use as big and "soft" of a flame as you can get.

Tempil sticks are a good way to judge the surface temperature of something without needing a thermometer. I think Markal makes them up to 2500F. They aren't cheap (not as cheap as Crayola, anyway), but they aught to last you a long time.

I've been thinking about building my own (very large) heat treat oven for some time now. Maybe 3X2X2 feet. Maybe a bit bigger. Something I could could fit an anvil in for pre and post heat when I weld them up.

Anyway, obviously it has to be a big insulated box. The tricky bit is getting even, controlled heat. I'm going to heat it with propane burners controlled by a kiln controller. Instead of the controller powering heating coils, it'll control the blower and propane valve solenoids. I'm fairly certain I'm going to build it into a hillside by my shop.

Sent from my Champion Forge using Tapatalk
Click to expand...
That sounds awesome! But not a project I want to undertake. I put my name on the 3 month waiting list at Jen-Ken
 
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