Propane forge for heat treat

Precision Edge Sharpening

Precision Edge Sharpening

Mail in sharpening service
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Knifemaker / Craftsman / Service Provider
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Jul 8, 2023
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Good evening all, sorry if this has been asked but i didn't see it anywhere. How does a small propane forge work for heat treat. Im not making any large knives at the moment, a few pettys here and there. would yall recommend a propane forge for this task. Ive been looking at the atlas forge. Its not huge if i ever wanted to do some larger gyutos or something down that line but i figure i can brick off the back and more or less use the heat coming out of the front to get it how i like it. Any thoughts?? thanks
 
Your best bet is to get/use a proper temperature controlled kiln. It’s important to not only get to a specific temperature range but to hold that temp for 10-15 sometimes longer depending on the alloy.
 
Oof there is a major problem, I neither have access to a kiln nor do I have anywhere close to enough dough. I’ve been using a hole in the ground a blower and charcoal and getting decent results. 52100 is relatively flexible
 
I have the Atlas Forge and I've used it for heat treat. But with very mixed results. One kitchen petty turned out so soft that I have to sharpen it almost every time I use it. Then a camp knife I made came out spot on. If you're just making the knives for yourself that's possibly OK. But if you plan to sell any, a heat treat oven is a necessity. Either that or send them out for heat treat.
 
While not ideal, folks have been using them for decades successfully.
Spend more time doing research to learn all the tricks and tips to maximize your chances for success and avoid the newer high alloy steels that are less forgiving.
Buy some books and read them, don't just do a 10-minute internet search and expect to find all the information you need. (I know I might sound like an old man lecturing a teenager, but....)
Invest in Larrin's book, Knife Engineering. And/or check out his blog, he has a couple articles on using a propane forge for HTing IIRC.
 
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OK, I will give you the advice you want. I'm not saying it is the best method, but it will work.
A kiln is better than a forge, but that does not mean a forge won't work. Forges were used to do HT for millennia before the first kiln was plugged in.

You didn't say what your "small forge" is. At the minimum, the forge needs to be large enough to hold the knife with some room to spare. It needs an adjustable propane supply ... and in the best scenario, air mix control. Tell us what type of forge you have.

You will need a magnet. A welding magnet stuck on the side of the forge is perfect.

You will need a pair of pick-up tongs or long handled pliers. Harbor freight has really cheap ones that work just fine.

Run the forge at normal temperature for 10-15 minutes to soak the refractory. Then turn it down to as low as it will go and hold a flame. This will likely still be too hot for a kiln type HT. If the lowest setting should not be enough to bring the blade to non-magnetic (that would be a good thing), slowly raise the gas supply until it is high enough. You would best do this with a plain bar of steel, checking for non-magnetic, and making it a bit hotter than that.

Place the blade in the forge and set it on the forge floor. Turn the blade over in about 30 seconds. Move it around and roll it over to try and heat the blade evenly. Try to keep the edge down so the spine heats up and the heat runs down to the edge.

As it starts to get red, pull the blade out every so often and touch the magnet. The point where it stops sticking is about 100°F below where you want it at quench. The edge area is what you are most concerned with, so watch it carefully and if necessary, move/turn the blade as needed to try and keep the edge and tip from overheating. If the edge is at the right temperature and the spine is a bit too cool, that is OK. If the edge and tip are overheated it can be a worse problem.

Heat to about one shade red above the non-magnetic point and quench. Quench straight into a container that is at least 6" deeper than the blade and at least 4" wide. The more the quenchant volume the better the quench. A gallon is the minimum. Two is even better for a small knife.

Immediately after the quench, temper in a toaster oven or the kitchen oven at 400°F for an hour. Cool in water and repeat the temper. Be sure to wipe off the oil and wash the blade with soap and water before tempering in the oven if you want to keep the wife happy.
 
Stacy E. Apelt - Bladesmith said:
OK, I will give you the advice you want.
Click to expand...
You are too kind, Stacy. How many times have you typed basically the same thing? (Or have you saved a copy and now just copy/paste?)

Sorry if I sound grumpy this morning. It might be related to me having to remind our 2nd youngest member not to move heavy equipment by himself and to clean up after himself for the nth time yesterday at our makerspace, and he still gave me attitude and asked me why I care what he does...
 
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Trust me, I would like a kiln but it looks like I can’t really get one under 2000 dollars, unless if a vevor, and I kinda have my doubts about it
 
Take a look at your local classifieds (facebook marketplace, ebay, craigslist) and you may find a used kiln for a reasonable price. It may be a pottery kiln, but those can still be used for heat treating knives (usually).
It's also relatively easy to at a PID controller and thermocouple to your gas forge and get at least some basic temperature control. You'll need a solenoid for your gas supply, and the more insulated/efficient that your forge is, the better it will hold a steady temp, but it's doable.
 
I’ve also been looking at red beard ops kiln diy video. He ended up with about $750 for a really nice kiln. My brother is an electrician and could help me with wiring and such
 
So you have a company called Precision Edge Sharpening but are making knives with subpar ht. Seems like a little bit of an oxymoron to me. I would recomend sending your ht out until you can set up a quality ht system including oven and Rockwell tester as a forge with no way of testing hrc is far from precise.
 
I’m not making knives to sell right now, I’ve only made a couple but I can see it as something I could get into, no I’m not planning on selling anything for a long time if ever. Sorry for the misunderstanding.
 
I think a person with a sharpening service could do great work and still not understand the details of knife making, in this case in particular, heat treating. My firsthand experience, I've been sharpening knives for years (not as a service) with success and only learned HTing details within the last year. Maybe I'm an oxymoron.
If you already have the forge, get a gallon of Parks 50 and try it, if you think you can make it work and are determined to. If you don't have a forge, don't bother because you will end up with mixed results, which sucks. Send your blades out for HT or buy an oven.
 
Precision Edge is a young feller with a lot of ambition. At 15 I probably wanted to set the world on fire in a month, too. He has a sideling sharpening knives and things.

He will quickly learn that things in knifemaking take time and money. The time is free, but the money comes hard to a 15-year-old on a farm. Actually, on a farm time is sometimes hard to find.

Pace yourself and learn one skill at a time. HT is a great skill to learn, but it can be done by someone else until you have the equipment or the skills.
Build your grinder and learn knifemaking.
When you have the skills to shape and handle a knife, then build a forge and try forging.
When you have those skills learned, then think about buying or building a HT oven.
Take your time. Some folks take several years just to get past those three steps.
 
I did this with pretty consistent results for a few years. I was just looking to make useable knives while I was learning.

So there's a couple things I would recommend to stay consistent.

1. 1084 is probably the easiest steel to ht in a forge.

2. You need to ht treat in very dim light and make sure each time you ht the light is the same as the last time.

3. Before ht, clean all the slag off of the blade so you can see the color consistently.

4. If you do any forging vs stock removal, you will have to thermal cycle the blade or it will not turn out.

5. The flame is your enemy. Use a piece of square tubing that is at least a couple inches longer that your blade. Leave the tube in the forge until it is heat soaked. Hold the blade in the tube edge up and test the edge against your magnetic. After non magnetic it will only take seconds not minutes to gain that extra 100 degrees you need.

6. If quenching in canola, preheat the oil to 120.

7. Remove the decarb when file testing!!! The file will cut into a hard blade until it gets through thr decarb layer so don't be discouraged if it doesn't skate immediately.

8. Before doing this to a knife, do it to a text piece and break it after hardening. The break will tell you if you're dealing with grain growth. The break should be powder sugar fine...if it has any grains you can see, it was too hot.

9. Don't take your edge down too much before ht...it's too difficult to keep from overheating. Nickel thick is a good place to start.

Temper twice for an hour at 400.

It might not be perfect, but 1084 is pretty forgiving. If you were close it'll make a nice knife, I've got several out there that have been holding up great for years.

Hope some of that helps.
 
I was able to pick up a kiln on FB marketplace locally for $150 and then added a new thermocouple, pid, ssr and some wiring. Maybe $300 total into it?

Look for some local makers, they may be able to help you out with the heat treat and stuff like that.
 
As far as I know, there are no local makers. However Francisco Vaz has been giving tips along the way.
 
Reach out to Jarod Todd. He offers heat treat services at a very reasonable price. I used him and Bos heat treating before I got my oven built, hardness tester, etc.
 
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