Mini Forge / Heat Treat Oven Experiment 

You're my shop teacher whether you like it or not.

Glad to hear that your thinking about a larger forge, I am looking forward to seeing the outcome.

Enjoyed that one John. I was surprised that you state that safety is My responsibility.....I always thought it was YOURS!! ;) Take care Mike

Awesome test! Looking forward to See that full build!

I like the way you clean a shop. I do that all the time.

keep up the good work!! I love the fact that you are trying something outside the box and using your mind to make something out of random "junk"

A few points: One, thanks for keeping the 'sped up' version of 'stuff that didn't work' in there. That was a good call. Two, if anyone IS worried about the danger of electric shock a transformer or GFI outlet would solve the issues :) Three. A dimmer on the element (or simpler series/parallel switching) would allow for it to be used for the annealing also. Four, thanks for taking the time to make these videos.

Interesting video John and enjoyable to watch ...thanks buddy

It's quite an interesting project John ! I'd be very interested in the heat oven you're building up. Keep the good work !

Love your experiments John!

I enjoy your videos on this channel. It's like I'm hanging out with you in your shop, but not getting in the way. Thanks, John!

Neat idea! A mini forge can always be handy to have!

Cool experiment John!

Great idea! I understand the danger - probably why I can't wait to try it! lol really like the experiments. being on a budget this will help my shop a lot.

i am always amazed how many things we have around us can be used in different way if you just put a little thought into it, loved the video. i am wanting to set up a safe space to be able to just play around with things like that myself but a am a over do it person so i figure it would be safe for me to have a bunker lol

You may want to look at Kanthal A1 wire when you build you bigger oven. I think it will stand higher temps than nichrome. It's fairly inexpensive so if someone doesn't have a heater to salvage a coil from they could still build on a budget. As I recall I used 18 GA in mine. Have heat treated 6 or 7 A2 plane irons with excellent results.

I was expecting that wire to burn off. I figured it was made to keep cool enough with the aid of air circulation and would burn off otherwise. And I will probably never try this myself. Good thing there are those who are comfortable enough with this stuff to show us wimps what happens when you take apart stuff that specifically sais DO NO TAKE APART. Nice video as usual.

Once again very cool and informative, I have an old heater I've been saving for some reason and now I know why.

Good timing on this! I've spent the last two weeks trying to soften dull files to make rasps out of them. Was going with a gas forge and vermiculite at first, which didn't work. Then tried a charcoal fire and managed to melt the files. I figured an electric oven would be the smartest way to go, since they're supposed to cool at a maximum of 20°C per hour, and I hadn't considered that the elements inside of an electric fan or hairdryer would survive those temperatures. But after wrecking the files i've started trying to case harden mild steel instead.

I look forward to more of these. You should make a V-42 Stiletto when you get this thing sorted out. I got a hand made one from Petawawa as a tour gift and it's a pretty cool dagger.

"This or any other project"... I love it!

If it's 440c stainless, 1850f for half an hour, air quench,then draw temper at 400 for 2 hours, love ur videos!

Cool idea John

Hey it got hot. I wonder if a burner from a hot plate or stove wood work??

The resistance of the coil may varies when it's temperature changes. The rated power should be close to 1500W at least.

I think you did a good job, if set up right seems it'll be much easier to run then a propane setup. one thing though, you said the 360/90 watts the element pulls is a far cry from the 1500 on the box, but that's just the heat element, not the fan and heat and whatever else all on high power could get to 1500 I'm guessing, right?

I think this is a marvellous video because, for someone like me who is colourblind, all that "heat to a straw colour" when tempering steel means nothing because I can't bloody see it right. However, temperature indicators are something I can read and very accurate so this is brilliant for me and cures my extremely severe and incapacitating disability when it comes to 'straw colour'. Best Wishes, Brendan.

Those white lightweight bricks you have are insulated kiln bricks; very nice stuff (and expensive!). I have searched for them locally but can't find those. What we have locally are the second brick you have; the dense thick fire brick. These bricks are not insulating although they do hold up to high temperature without cracking

I think if you try to make another coil connected in parallel with the final one that you have made it will give you higher temp in shorter time say one at the top and the other at the bottom what do you think !

great video. and those were the most enjoyable "lawyerly" warnings I've ever heard. "If ... it's your fault." awesome. sad that we're at this place in society at all. makes me think of all the car / motorcycle ads with the "professional driver on a closed course. do not attempt" warning, and it's someone moving maybe 30 miles an hour. oh, the horror.

Wait...if I hurt myself doing this it's NOT your fault? These videos are great, and please keep making them! I'm going to build the heat treat oven you made in a later video. It's perfect.

Thanks John that was cool..

sorry to comment late to the game. thank you for this vid. did u connect the heating coils directly to mains power? or was there other circitry involved ? thank you

John, do you ever sleep? =) I enjoy your videos a lot; thanks for sharing your time and talents.

I'm going to do this. I had an old heater that went bad. I took out the coil for a reason unknown until now. Do you think it gets hot enough go fofge?

Without a doubt I will not be attempting to build a mini forge given that I am not even comfortable using the self clean function on my oven. I am glad you do these things as they are entertaining from a distance. BTW, did you ever get to the dump?

Hi, nice video. If you don't know what temperature to bring it up to; a crude method is to take a magnet and check the heated material with it. When it is not magnetic anymore it reached the point when you can quench it. When this happens you are at about 1380 Deg F. (about 750 C) - Austenitic state.

to simply check if the knife is hot enough to cool it down is to use a magnet. when it stops being magnetic, it's time to put it in the oil. just a trick a lot of homemade knifemakers use. if it is still too "cold" it will not make much of a difference.

Impressive first tests, have you considered case hardening for putting a hard layer on the softer blade material. Not sure if that would work for a knife, we did it in shop when we made tools like screwdrivers, I recall, but that was many years ago. Love the videos and variety.

If you wired the unused portion of the heating element in parallel would it not double the heat output?

Now that is really interesting.

Love the into warning music

I have designed several furnaces of that sort several years ago. If memory serves me correctly you are probably looking for an off fire temp of about 1200 deg C to do your heat treatment. Looks like you already have a controller. The nichrome toaster wire you had is fine for experimenting but will not last when trying to do some actual heat treatment. You will need a heavy duty electrical service to do one properly. The volume and mass you are heating will determine to a large extent what your power requirements will turn out to be. Then you also have to consider at what rate you want the thing to heat up at. Best if you have a controller that will allow programming in ramps and soaks so that you can anneal and soak the heat as needed.

I highly recommend you look up the Waterglass videos about making a coffee can forge. I plan on making one this summer. Obviously I'll be using a torch instead of electric power. A friend of mind has jumped in with both feet into the whole blacksmithing thing as a hobby and loves it. I'm getting him to make some "iron" handles for me for a little storage chest I'm making. I really like the knife stuff you do ... perhaps a new channel "I Forge It.ca" ;-)

10 vid in a row. i now sub

Hi, im a 15 year old beginner who likes making knives from old files and lawnmower blades. What do I need to know about heat treating? Im now at the part that is stressing me out the most, quenching in oil and tempering, but im not exactly sure what I should do and at what temperature. Please help

Going way back. I remember 1333 F as the critical temp for steel. So that would be the absolute minimum temp, At that temp, the transformation to austenite would take a very long time. The higher you go, the faster things happen. Aim for 1400-1450 steel temp, approx 1hr for every inch of thickness. If you have 300 stainless, don't bother, its not hardenable.

Fun stuff. Now you just need to try using a coil from an old microwave to build an induction heater. I'm guessing that'd work too, although it might risk melting your blades. I think "Grant Thompson - The King of Random" has a video or two on forging using that method. If you turned the power down it might work great for heat treating.

Great one!

Incidentally, insulating fire bricks like you have and non-insulating fire bricks are a completely different animal. In my experience, insulating fire bricks are absolutely essential. Without them, so much heat is lost through the walls that high temperatures are not achievable without super high power.

so, it looks like that element would continue to heat, perhaps reach a maximum heat inside the chamber. I suspect, however, that the interior would definitely be hot enough to melt aluminum (1400deg). Did you note a max temperature where your element wouldn't continue heating?

What if you were able to mount the other half of the original coil to the underside of the top brick and plug it in separately. This could aid it getting the temperature to rise.

Most hardenable stainless steels need to be heated between 1950° & 2150° they don't need to be quenched because high chromium steels are air hardening or air quenching steels.

Thank you for the entertaining video. To make it hotter, you could just plug it into 220V ...

The resistance of the coil changes with the temperature, I think it'll be more accurate if you measure the amperage when it's red hot to calculate the watts.

Hi John, I really like your videos. I'm looking foreward to making a knife, that I want to heat treat and wanted to ask you, why you use motor oil. Does it have any advanteges to water? Jonas from Germany

For a filiment, the resistance goes down considerably as the temperature goes up, if I recall from EE a long time ago, so the watts should be measured live with a current meter for a more accurate result. Interesting oven though, will be interesting what you end up with.

For hardening steel heat it up until it is not magnetic anymore than put it in oil. great vid goad idea

I believe you quench the metal when it is non magnetic, I do not now what that temperature is

i think that is pretty cool.

So tragic that today one must spend so much time doing disclaimers and safety warnings for what was just common sense a generation or two ago. Good test.

standard high carbon steel which is hardenble should become non magnetic when it reaches the correct temperature. you will also have to stress relieve it after you harden it or it will be too brittle and snap.

Sometimes the Ohms law doesn't apply to reactive circuits. There could be a way to manipulate. Any capacitance, parasitic capacitance, impedance all interfere with the Ohms law. The idea is great. Thank you.

Doesn't the 1500W also include running the fan? Although I'm sure you're right either way - nothing that is supposed to be powerful ever meets the marketed specs.

you could use this small oven for tempering maybe ;)

Impressive. I was sure the heater element would burn out because it was not cooled.

*"DON'T TRY THIS IF YOU ARE IN ANY WAY, SHAPE, OR FORM, STUPID!"* LOL!! Great video! [Stonehenge (snort!)] Keep the entertainment coming, John Heisz!

What's the max temp you have reached

You want to heat it to its Curie point, or the point at which it loses its magnetic property (a bright red). Check with a magnet!

quick and dirty trick for most steels, is to check it with a magnet, when it becomes non magnetic, your in the proper quenching ballpark.

If I'm counting correctly, this mini forge reached 1400 in arround 23 minutes? :)

Could you do the same with a toaster?

Touch the blade to a magnet when it's as hot as u can get it and if its still magnetic it's not hot enough

I'm a process engineer that works with heating elements, temp increasing means resistance decreasing, which means current increasing. Heat generated is proportional to the square of the current, so that means the resistance will keep going up and its a positive feedback loop until you reach a balance point where the heat generated is no longer trapped effectively by the material. Measuring the resistance at room temperature gives no indication of how much energy it will use when warmed up.

You forgot to account for the fact that the more heat, the more resistance.

Hi. i am also in canada, finding a hard time trying to source the k 23 bricks. would you mind telling me your source?

Current needs to be measured during operation. Resistance drops when heated.

ohm's law is a bit different for AC current but since it is only resistance the effect should be small. My guess is the resistance is way lower bout 10 Ω

Why not try to build an induction heater?

Quench in water, temper in oil - and you can't harden most stainless or low carbon steels.

2 each 1/2 coil in parallel.

Can it reach 1550 degrees f? I have the exact same broken heater but 1400 is pointless for my sake . Cool shit tho.

We all see that petroleum jelly back there ;) ;).

Most stainless steels are low carbon and won't harden by heat treatment

I was just waiting for the screws to soften and drop the heavy metal bit/blade directly across the mains! lol

But how does it vape ;)

Seems like 1400 is hot enough maybe just need to leave it in longer and do a magnet test before quenching?

Resistance will drop as soon as it gets hot! So it will probably have the claimed 1500W!

quench carbon steel when it is just non-magnetic.

I tried this at home and set fire to my pubic hair. But I'm a real man, I put the fire out with a hammer.

heat until it is no longer magnetic then quench

There's a simple reason why it's rated at 1500W. Two words: Marketing wank.

The resistance of the element drop as it warms. That is why your math doesn't arrive at the rated 1500W.

Sounded like my dad at the end ...

*"simple heat treat for homemade blades."* optimal temp varies depending on type of steel but for most high carbon steel this method should produce high quality results. (I recommend 1075 for beginners) -you need a hot enough forge - a large magnet -a metal container of oil -and a a "liquid nitrogen container" for this you need to cut a 2 liter bottle at the thickest part of the neck. have a pvc pipe about 3" diameter with holes 1/4" diameter drilled all over it and stick it into the 2 liter bottle, filling the sides with broken chips of dry ice, and fill the container with isopropyl alcohol, this creates a imitation liquid nitrogen ///WARNING!!!/// -> DO NOT TOUCH WITH SKIN!!! DANGEROUS AND WILL FREEZE ON CONTACT! -and also a oven ------------------------------------------------------------------------------------------------------- 1) heat metal in the forge until cherry red and/or non magnetic, allow to air cool to relax the molecular structure and repeat step 1) 2) stick back in the forge for a few seconds, and as quick as possible under 2-3 sec get in the quench oil edge facing down and move back and forth, not side to side as this could cause warping. 3) a few seconds after the sizzling stops, take out of the oil and into the "liquid nitrogen" container tip end first. (when steel is heated the molecules relax and realign, and quenching it shocks the molecules making them form tighter, and bringing the steel to subzero furthers the molecular change and a tighter molecular structure) 4) once the steel is cooled test with a file, if it skates instead of bites then the steel took the heat treat. 5) set the oven to 420' and temper the blade for about 2-2.5/hrs to soften the steel back a bit to prevent brittleness. --------------------------------------------------------------------

You can't use ohm's law on AC power. AC power is measured using RMS power.

Keep in mind not all steels can be heat treated. You should know the chemical composition of the steel, specifically how much carbon it has to know the optimal austenitization temperature. If the temperature is too high you will get larger grain size in the metal which again leads to undesirable mechanical properties.