Poor Man's Heat Treating Thread...

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
Lot's of guys are just getting into knife making and don't have all the tools. We need a way for those guys to heat treat a blade with minimal tools or experience.
I put this together recently and will post it for review and reference. Please add in your experiences, pictures or techniques on getting heat treat done with the poor man's attitude in mind.

Thanks

Poor Man’s heat treating of 1095 – 1080 - 1084
Written by Tracy Mickley, owner of:
Midwest Knifemakers Supply, LLC at www.USAKnifemaker.com
Knife Dogs Knife Forum at www.KnifeDogs.com

This is remarkably easy and can be done a dozen different ways. A simple propane torch, magnet and bucket of oil or even water will get the job done. The more precise you are about heat treating your steel, the better result you will have. Use the internet to research different ways to heat treat. Visit most any of the knife making forums and search for heat treating for 1095 1084 or 1080. They are all so close the only difference will be slightly different temperatures and resulting hardness.
Normalize:
Normalizing steel resets the steel crystalline structure and will redistribute the carbides to a uniform size across the metal structure. Uneven crystalline structure creates stress and weakness. Uneven carbide size and distribution lowers the cutting performance. Normalizing is such an easy step it is worth doing. Heat to 1550F to 1600F depending on the steel. Allow to cool slowly in still air. Done. Generally, steel that comes in bar form from a mill is often annealed and probably doesn’t need to be normalized. It still wouldn’t hurt to do it. Read on for how to do this poor man’s style if you don’t have a forge or heat treat furnace (oven).
Annealing:
To anneal, heat to 1475F to 1500F, cool very slowly by leaving in a furnace (heat treat oven) to return to room temperature. Your rate of cooking should be 50F per hour at most. I heat mine to temperature and then it in a bucket of vermiculite to cool slowly. Some guys use a tub of lime. I put in some scrap steel I have heated up to help add heat mass and slow down the cooling rate.
Hardening:
Heat to 1475F to 1500F (steel type depending) until the metal is just past non-magnetic. Non-magnetic is around 1425F. A propane (or MAPP gas) torch played evenly along the blade will get the job done. Try to get the heat color evenly across the blade. You don’t need to harden the entire knife blank. Just the blade is good enough. Don’t worry about hardening the handle. It will never cut anything and it will be more than hard enough for use as a handle. Still, you can if you want to.
Alternatively, you can make a poor man’s forge in charcoal BBQ grill using a hair dryer to fan the charcoals hot enough. This is amazingly easy. Pile up some charcoal in your BBQ and get them going good. Aim your hair dryer at the charcoal and turn it on. See how hot the coals get from the blower on the hair dryer. Some guys will take a pipe and put one buried in the charcoal and duct tape the other end to their hair dryer. This forces air up through the charcoal and is pretty close to genuine blacksmith forge.
Put your knife in the pile of charcoal and heat it up. It won’t take very long at all. These steels doesn’t need a long soak time. A couple minutes is enough. In practice, you heat the blade and keep touching a magnet to the blade. When the magnet doesn’t stick any more, give it a minute more of heat and then quickly plunge the blade into your quench oil. Fire will flare up where the hot blade meets the surface of the oil. Be ready for that. You should slowly agitate the blade up and down or side to side along the thin edge. This helps remove any insulating air or gas bubbles. Do not agitate side to side as the soft metal can actually warp from the fluid being cooler on side versus the other. Agitate so the fluid moves evenly over both sides of the blade. The blade is very brittle at this point. If you drop it on hard surface, it will crack or may shatter like glass. When it reaches 100F or less, start your temper cycles to reduce the stress. Handle your blade carefully at this stage or you may end up with a cracked or broken blade. It will help if you pre-heat the oil to around 100F. This can be done by heating up some junk steel and sticking it in the oil a couple times.
Temper:
Heat up the blade for two cycles of two hours each. Many use their kitchen oven for this. Put the blade in the center of the oven away from the elements. Make sure all the oil is cleaned from the blade or your house will smell like oily smoke and your knife making career may be cut short by the boss of the kitchen. Consider picking up a cheap table top oven at the thrift store if you are going to make more knives. The temperatures for house hold or small table top ovens are often wildly inaccurate. Use an oven thermometer to get close to your target oven temperature. Allow the blade to return to room temperature between temper cycles. There is enough difference in temper temperatures here that you want to check out the specific steel for the proper temperature to achieve a desired hardness. Most custom knives tend to be hardened to 59RC for a good compromise between edge retention, toughness and sharpening ease. A harder blade, say 61 to 62RC will generally cut longer between sharpening sessions. It will also generally chip easier along the cutting edge. It will also take longer to sharpen. A softer blade, say 57RC, will chip less, be easier to sharpen and will bend quite a bit more before snapping. The edge will not stay sharp as long.

More on Quenching:
Quenching oil is very sophisticated in design and application. If you can afford it, buy some and use it. In place of that, use low viscosity motor oil or even canola, vegetable or peanut oil. It will work. It won’t be perfect and veteran knife makers will tell you to use dedicated heat treat quench oil to get better results. I recommend that also. I also know most any oil will work “good enough” for our purposes here. You can even use water and something called “interrupted quench” but let’s leave that for another time.
Watch out for fire flaring up during quenching! There will be fire and smelly, heavy smoke. Be ready and be safe. Do not breathe in the fumes. Wear eye protection. Wear heavy leather gloves and apron. Have a fire extinguisher nearby. Many shops have been lost to fire by someone knocking over burning quench oil. A surface fire on quench oil is not the end of the world. Simply put a lid on your quench oil container to smother it and put out the fire. You should end up around 65RC in hardness. Visit Youtube.com and search for “quench knife” to see dozens of short videos on what to expect. This isn’t that hard but you do need to respect the hazards.
Blade Bending:
Chances are your blade will be perfectly straight from quenching. Once in a while, they warp a little. Check it during quench before it cools down to less than 200F by looking down the spine. If you see a warp, now is the time to bend it slightly back to being straight and it should take.

Have fun. Be safe…
 
Nice write up.

Here's my $0.02 worth:

Making a 1 or 2 brick forge is pretty cheap and can be used for normalizing and hardening.

I heat my quench oil to about 130°F. I have a metal pan so I heat it on the side burner on my BBQ. Alternatively, you can heat p a chunk of scrap metal and stick it the quench oil.



Ric
 
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Well written.
My bit to add was I used a bucket of vermiculite or sand in the Normalize process. after bring to heat. Just stuff it in tip first up to the ricassio area to get a nice even cooling.

I had/Have good results using ATF fluid as a quench in a metal paint tray for differential heat treating.

Laurence

www.rhinoknives.com
 
... Finally a thread that's right up my alley. LOL

Use a muffle and some alternative temperature gaugings along with the magnet, at least until you train your eye.

What kind of budget are we on here?
 
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... Finally a thread that's right up my alley. LOL

Use a muffle and some alternative temperature gaugings along with the magnet, at least until you train your eye.

What kind of budget are we on here?

I thought you might like this one. I have started to "learn me up some" on heat treating.

A poor man's budget pretty much means anything other than using a regular forge or oven/kiln.

Tell us (pictures are even better) about a muffle and alternate temperature gaugings. I will be the first to admit I just can't use heat color as a guide. I am untrained I guess or possibly slightly color blind. I'm going for environment vs genetics on that saying I am just untrained.

I guess this might include building a poor mans forge to heat things up.
 
Maybe a mention of decalesence and recalesence which is a better guide than a magnet. Tai mentioning about the trained eye made me think of it.

Doug
 
This is almost exactly the way I've been doing my heat treating. I have a small BBQ grill and a hair dryer for hardening. To anneal I've been using cat litter. You can buy a small bag for next to nothing. I've been using Canola Oil to quench. I've done maybe 4-5 blades this way. So far I've only had one that has really heat treated correctly, but it's really me learning and not the process.
 
Well written.
My bit to add was I used a bucket of vermiculite or sand in the Normalize process. after bring to heat. Just stuff it in tip first up to the ricassio area to get a nice even cooling.

I had/Have good results using ATF fluid as a quench in a metal paint tray for differential heat treating.

Laurence

www.rhinoknives.com

I'm confused. Isn't that annealing? I thought normalizing relied on an air cool rate?

Learning every day. :confused2:


:biggrin:
 
Well, I am glad I saw this thread. It is something that can be discussed. I HT the poor mans way. There are some pros and cons to it but IT IS DOABLE. I even heat treat O-1 with a torch and get great results. However, I am planning on snagging an oven from USAKnifemaker

Now having said that, I have the belief that you are not getting the best out of your steel, but you can make a great knife.

1095 from Aldo. I quenched in a bucket of water.

IMG_0566.jpg
 
Well, adding the sand or vermiculite to cool the blade in from austinizing temperature isn't really annealing but it isn't really normalization either. True annealing take a bit slower cooling than that. Personally, I find that normalization gives a soft enough steel for grinding and some feel that annealing from critical will cause carbides to be large. This is different from a sub-critical annealing which is sometimes referred to as spherodizing.

Doug
 
I hope you don't get your vermiculite from Libby, Montana. It has asbestos in it, called tremolite. A lot of people here have died because of it. It's not just a "nuisance" dust and It will hurt you.
 
So, I have a question on the straightening step. You remove the knife from the quench oil and bend it to straight while it's still hot? (above 200 degrees F) I feel like that would result in a broken blade given how brittle hardened steel is. Am I wrong? Can you also clamp it straight while it is in the temper oven? I tried that on my last blade and it seemed to help. Next time I think I'll try clamping with a little bit of a bend in the opposite direction. Is this an ok way to straighten?
 
The muffle is simply a thick walled mild steel (or ceramic) pipe suspended over the coals (with a thermal blanket draped over the top) or through the coals or gas forge chamber, with the back end plugged.

* Creates an opened space to insert the blade, protecting it and making it easier to see.
* Helps even the heat out through diffusion.
* A piece of wood can be placed at the back of the pipe just prior to inserting the blade, to help create a more reducing shielded type atmosphere.
* Cuts out ambient light.

Alternate temperature gauging:
* Ceramic cones used to judge temps., when firing clay.
* Tempilstiks.
* Thermocouple with a meter.

Wood/charcoal:

ModMufflefurnace.jpg


Mufflefurnace015a.jpg


DSCN3179.jpg




Gas:

Mufflefurnace012a.jpg


DSCN2642.jpg


DSCN2645.jpg
 
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hi,
my toosense. collect all the safety hints we can. from little stuff like a lid for you quench oil container(only safe way to put out a fire), good gloves and tongs, maybe some electrical so we are constantly blowing fuses or worse.
scott
 
Peter, on straightening while the blade is still hot from the quenchant. The goal is to straighten the blade between the Ms and the Mf point on the cooling curve. The conversion of a crystal from austinite to martnesite occures very quickly but not all at once. When the blade is still just under the Ms point there isn't a lot for martensite that has been formed and the blade is still relatively soft give you the ability to straighten the blade. As the blade cools more martnesite forms and the steel becomes harder and more brittle so you time is limited but you may have 20-30 seconds to get this done, depending on how hot the blade is when you remove it from the quench tank.

Doug
 
Doug, thanks for explaining that! That makes a lot more sense and I think it will greatly reduce some frustrations for me. : )

Peter
 
Id add to read the scale pattern on the quenched blade, file testing for harndess, and etching in ferric after tempering to read the ht, and testing for performance against a known good blade, all things that are cheap or free
 
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