DIY Heat treating oven help needed

P

PandaRen

Joined
Apr 10, 2021
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Hello everyone! After 2 years of inactivity on the forum' I'm back requiring more help!

SO, I've managed to make my 2x72 using Dan Comeau's plans and help and have gotten pretty used to it by now. Gotta say it's fun to play around with this stuff! SO far I've made some trial pieces to test out how to actually work the stuff and see how bad I am haha. A few things came out pretty decently!
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I very much so love this dagger. Made it from Magnacut with brass fittings and a G10 handle. Those of you who saw the first little thing I made can see the inspiration + classic gamblers knife.
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Went for a more Bushcraft type knife.
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Trying out different shapes to see what I can manage.

NOW, these were all sent to the guys at Heattreat.ca which are amazing and helpful. The prices are also pretty damn fair so I didn't consider trying to to HT myself until this happened....:
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This thing just made me go wow. I had a 3V piece laying around that I cut out as a cutlass trying to do something semi complicated for a challenge that just wasn't doing it for me and it go reground into this. And I fell in love. This thing is sadly about 21" long (HT.ca can only go up to 20) and I had to adjust it to a piece that was already all cut up to make something nice. This one I could send to the guys in Alberta as the tang is short so the total length is about 19" I believe but even there, the prices at this size go up dramatically. Can't ship in a flat rate box and the costs are way way higher. During the drawings I got into East Asian swords a lot and based this off a type of sword/machete.


Long story short (hah!), I want to build a Heat treating oven that is about 5" x 5" x 32"-36" long. I've been scouring the forum and the web for weeks looking at the info available and sadly, I suck at math and am no electrical engineer so I come looking for help for the important stuff!

The shape is a standard one: 2 sides are IBF23 full bricks with an indent top and bottom then top and bottom are bricks inserted into it. The 4 pieces will be individually mortared together on the length so they can be taken apart and changed. It will then be seated on 1" 2300F ceramic fiber boards. The whole thing will be in a 16g steel box with removable top

I figure this has to run on 220/240 as it is pretty long. Design is pretty much based on the Paragon Km36-T as its a long box.

I had questions for those here who are knowledgeable:

-Do I need zones seeing how this is a long unit?
-Does making a modular unit work? I've seen some kilns that can pile up like Constructicons and make a longer kiln. How viable are these and could it work well? This option seemed interesting because having a short and medium kiln would be more efficient outside of long blades. Use them apart mostly and join them when making a sword.
-The god damn coils... I can't for the life of me figure out how big/long/whatever to make them with all the formulas out there :| Also, I saw the build by JKTKnives where he has them on top only wrapped around ceramic dowels and was curious as to how effective that was? How do those compare to have 2 rows on each wall. Or 4 rows?
-Basically, I can build the whole shell and stuff but as far as the electrical things, I'm somewhat clueless. Here I thought hooking up a 1.5hp motor to a VFD could be complicated...

I looked at the kit from Auber Inst. https://www.auberins.com/index.php?main_page=product_info&cPath=58&products_id=677 but wasn't too sure and didn't know if everything in there was actually useful. And also: the 1 zone thing. I saw some people saying the PID on there wasn't very user friendly also. Speaking of which, depending on what I go for (on or more thermocouples) and looking at the PIDs, the Genisis 2.0 seemed like a good one for not TOO much money + a kidney. Are there others that are more affordable PID and can work well. the TAP is almost twice as expensive and I'm in Canada so we get screwed hard.

I wanted to just get the KM36T but the cheapest found was around 2300USD which is 3100k+ on top of the insane amount we'll have to pay at customs. Or they go for around 5K from the few dealers we have here.

So have away gentlemen! I'm all ears. Thanks to anyone who's willing to help with this project. We have basically 0 community here in the province of Quebec.
 
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There is a lot to learn about building a HT oven. I would change your dimensions. 7X5X36 would be wiser. The tighter the chamber the more specific you have to be about even heating. Zones are great, but add another level of design/build difficulty.

Read everything you can pull up in a search here. Use the custom search engine in the stickys.
 
There is a coil calculator spreadsheet on the heat treat oven page at dcknives. I think the equations are basically correct, but in my opinion, the coil length should be interpreted as a minimum value. I stretched my coils a good bit more than the 2x factor in the spreadsheet.

If I ever build another oven, I will go with JT's arrangement for the coils. I think Drew Riley Drew Riley built one with the coils on top as well.

For a really deep oven, a 5x5" opening seems small. My opening is about that size and getting an 18" blade in a foil packet in and out is a bit tricky already.

I have an Auberins PID controller on mine. I looked at the programming manual for the ramp/soak version and decided it was too complicated to use so I went with the regular one. That works well enough and does not require looking at the manual every time I use it. BTW, the link to the kit in your post did not work for me.
 
"... BTW, the link to the kit in your post did not work for me."

Just as well - he should not be posting links anyway.

I agree that JT's top coils on ceramic rods is a very good method of the heat supply. No sag and no grooves and staples. I also concur with JT that a counterweighted door is a good plan. You probably don't need his argon insertion, but it is also a good thing if you want to go there.

Ramp/soak is nice to have but a simple PID controller will work fine for most steels you HT. You just have to watch the temperature rebound and use a timer to do the HT.

Here is the JT oven build thread: https://www.bladeforums.com/threads/heat-treat-oven-wip.1407817/
 
I did not know that you couldn't post links? Sorry. It's the Auber kiln kit that has the SYL2325P PID and everything in it almost plug and play.

I've already looked over JT's build before and went over most of the common DIY posts here and around online. I was curious about top coils as to me it seems the heat would be mostly at the top no? Doesn't that mean the top would always be hotter and blades going up would have the edge hotter? I figure there's some sort of physics involved here when reaching higher heats that it acts a certain way and this isn't an issue? Otherwise it seemed like a damn good plan.

I've tried looking at Dan's spreadsheet but the data on it goes up to 16 and I figured 14-12 would be better for a bigger build?

Then the zone issue: I can't find anything on someone building a zoned one or if it's THAT much better for the hassle. Hell, I was wondering if having a different PID for each section would be an option lol. Or 2, as I figure most of the time I wouldn't use the full length, it shouldn't be hard to close off one section and open it up when the need comes. Brainstorming here.

What I had figured build wise was this:
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Orange is the outer brick layer, with 1" ceramic fiber boards all around (yellow). Blue is of course, the elements (the big parts are the coils, slim are unwound wire). Not sure if I'd use a fold down door or a side open one as I'm not a welder/have the place to do all the fun metal work so still have to go with something simple. All this looking is making me want to take an intro class in welding though because it looks so damn useful. Anyways, the drawing is to scale, 1/4" for 1/4". If I went the zone way, this seems like a layout that would be effective to someone who knows jack about electricity and thermodynamics! The elements could come out from the bottom and be hooked up there as opposed to out the back where it's too far for the first two sections. Meaning I could do the wiring and such under the oven.

Coil sections are about 11 1/2" except the first one because I'd intend the door to stick in 1" for a better seal.

Following Stacy's advice, the opening would be 7 x 5 and I figured angled channels would hold the coils better:
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Now if I ever get the math down (or you know, some gentle soul helps me) for the coils as a whole, if I go the 3 route, I doubt it's as easy as just cutting it in thirds and voila?

But before all that, I'm very curious about the top coils thing and cannot find any information about it anywhere outside the two builds posted on this forum froM JT and Thadbow. Is there a place to read up on it or does anyone have any information as to it's ups and downs? Because it really seems like a much simpler approach no? It must change the math on coils because now you have a whole flat surface (kinf od) as opposed to 2 rows each side. The chamber probably has to be a bit higher and not as wide? Any links?
 
That controller will work. We are not allowed to post links to sales sites unless they are Bladeforums dealers.

Top coils radiate the heat down from the top evenly. Spacing of the loops is easier and more accurate than stretching. Wiring is also simpler. The ceramic rod heats up and acts as a radiator.

The oven refractory soaks the heat and the entire interior becomes an even temperature.
A sufficient soak time at temperature is very important in doing HT.
In a properly soaked oven, a bar of steel will end up the same temperature throughout after 10-15 minutes in the oven.
Most of us place the blades vertical with the spine up and the edge down, point toward the back.

Sufficient volume for some convection is needed, which is part of why 5X5 seems a bit small to me. I know the Paragon KM-36" oven is 5.5X4.5", but they are building one with a good controller and years of testing and experience. I still recommend 5" high and 7".
 
I was looking at getting the Bartlett Genesis 2.0 or Genesis mini depending on which way I go. The math also seems to be simpler with the top coils from what I can tell.

If the coils are on top, shouldn't the oven be higher than wider? Then again the wider makes more element over the surface so it should heat up faster? The idea seems more and more appealing honestly as whatever choice I make this way can easily be modified later if I want to. I'm guessing the rods used by JTknives JTknives were 3/8" because his slots seem to be 1/2" wide. Going this route doesn't affect anything else already planed... I think I might be sold.

As it stands, the dimensions are .416 x .583 x 3 = 0.728 cubic feet. At 6000watt c.f. that would give around 4400 watts? There would be 23 x 8" rods (7" exposed) on the roof. The shop is equipped with lots 220 for a bunch of giant tools so I'm pretty sure I can get a good outlet, I'll go take a peak in a few minutes (Canada so not sure if we have 220 or 240?). This is the part I can't compute properly yet. I'll go over the formula again tonight and try to make sense of it.
 
You can modify Dan's sheet to add in thicker gauge wire, but the cells you want to change are password protected, so it requires a bit of hacking.

At 4,400W (240V), the stretched coil lengths for an ID of 3/8" are 122" and 186" for 14 and 13 gauge Kanthal, respectively. That's too long to fit across 23 7" rods for 13 gauge. I'd be tempted to go for 240V/25A/6kW with the 13 gauge wire for a coil length of around 136".
 
Yah I tried to play around his doc. and was unable to lol. Would have saved me a lot of trouble if I could... I think.

So if I understand this properly, at 136", each rod have 5.913 inches of coil on it? - a little bit less for the 1" unwound between each rod. Is that enough space to stretch the coils over the rods? I thought you needed at least twice the size of the wire in space. Also sounds like I'd need a giant spool of wire to make the coil lol. Is 14gauge too thin?

At this point, I was really considering going with 3 elements/3 zones meaning the front would have 7 rods and then 8 rods each. This brings me to another question: would shorter coils make them last longer or would it actually make them get used faster since (in theory) the power in them would fluxuate more when they adjust for the different zones (IE: the front one would probably wear out faster since it's near the door)? Would 14g be good for this then? Seems like a good middle ground for size and life expectancy?

THEN ANOTHER QUESTION, do zones act like different elements in calculating the power and series / parallels? do I just cut the overall math in 3 (or pro rata with the 7-8-8)?

Does anyone have links to rods that can fit? The links given by JTknives JTknives are dead and the ones mentioned by T Thadbow I can't seem to find (and seem quite expensive...) Mcmastercarr has Mullite tubes at 34$USD for 24" which makes it about 480$CAD for the rods which is.... a little way too much.
 
The 136" was for a coil with a 2x stretch factor. I have attached a zip file that has an unlocked spreadsheet in libreoffice and excel format with the 13 and 14 gauge data in it. Please, double check the values and use at your own risk.

With multiple zones, it will be a lot harder to fit the coils. Multiple zones would be parallel elements. For a fixed voltage, longer coils will last longer, not the other way around. The longer the coil, the higher the resistance, the lower the dissipated energy, the higher the lifespan.
 

Attachments

Thanks a lot for the doc!

So I'm reading the sticky by SteelSlaver about the elements:
Series and parallel are also important fundamentals you must understand when working with more than 2 elements.

SERIES means in line or one end of each element is connected to the other and power goes from one power line through one element then to the other element, through it, then to the other power line.

PARALLEL means the elements are connected together at both ends. Power goes into both from the same power line and leaves both at the the same place at the other power line.

example 2 8 ohm elements connected in series would measure 16 ohms (8 through the 1st then 8 through the second)(twice the length) use less than 14 amps and make around 3000watts.

2 8 ohm elements connected in parallel would measure 4 ohms (goes through 2 paths and is twice as easy) use 55 amps and make 12,000 watts.

Same 2 elements way different results
Click to expand...

So what I understand is: that series means the two elements form just one circuit, each one of them has one end connected at the power source and the other end connected to the other element (like an extention cord). Parallels means both elements start and end at the same power source separately.

Going by the spreadsheet, having two elements for the same desired output means DOUBLE the amount of wire? As in each separate coil has to have the same Ohms as the singular one would for 1 element? If I put "2" in the elements portion of the spreadsheet, are the calculations done for the whole or per element?

And here I was at the point of starting to understand ONE element math... -_-
 
I think you are misunderstanding a ZONE system.
Each zone has its own PID, TC, and coils. They are not interconnected in series or parallel resistance-wise. They only share the common power cord and main switch. Consider it three HT ovens sitting end to end. Each zone is 1/3 the oven heat/power, so if you wanted a 6600watt oven, each zone would be wired with coils for 2200watts.
 
The TAP and Genesis and probably other PID controllers are able to control 1-3 zones. I know each ZONE has its own T.C. which is how the temperature is regulated between each of them. What I do not understand is the power distribution and such seeing how they are all connected to the same control board in this case. Also, I seem to realize that Wattage value is inversely proportional so coil size: less wire = higher wattage (because it takes less time for the energy to travel from end to end?). One thing I had not considered because, well I'm an idiot, is the coil size :| Right now I've been going around looking at the 0.375 and wondering how can that fit in there at all but going to .5 cuts down a LOT of length. Is that something viable to have a 1/2" coil (I'm guessing the spreadsheet considers ID and not OD? or is the .375 a coil that was done on a 1/4 dowel?) What's an acceptable coil size seeing as this is just one surface being covered?

I have a hard time getting my head around the math though like if let's say I got with H Hubert S. 's proposition: 240V/25A/6kW with the 13 gauge wire I just didn't understand how I couldn't just take that, separate it in 3 and have the same wire length... now I kind of get it a bit more but it's very counter intuitive :D Now I see that it seems it's the opposite? If I want those same specs, I would need like 5 times the total coil length. Or let's say, go to 2 3000watt zones with 16gauge wire would give about the proper amount of coil that fits.

Make sense?
 
It is not intuitive.
I would suggest reading up on it and calling the folks at Aubreins or Genesis and discussing how it operates.

Don't try and calculate anything until you have decided the system type (single or multi zone) and the parameters (voltage and desired wattage).

There is a lot more to know than just the coil size and length in building a HT oven. LOTS more!

If it is not absolutely clear how every part of the system works and how changes affect things, don't do anything without someone to help you. Asking questions here is a good way to learn more, but it won't replace a direct contact with a person to show you hands-on.
 
I think the spreadsheet is based on the coil ID, not OD. I will check when I get back to a computer. If you want two zones, I think you can either calculate a parallel setup with the spreadsheet or a single coil with half the wattage and make two of them. The result should be the same. Using a larger coil diameter is a good way to fit more coil in the oven.

The thicker the wire you use, the longer the coils will last. The spreadsheet does not calculate surface load, which is an important parameter. You can find a Kanthal handbook online that has recommended values for surface load. I forgot the details since I built my oven, but I vaguely recall that the spreadsheet will exceed recommended surface loads for the given wire sizes for higher wattage coils. I think that 3kW for 16ga might make for a short lived coil because the surface load is too high. You can add the calculation to the spreadsheet by dividing the wattage by the surface area of the coil and then compare to the handbook recommendations.

If all of that sounds too complicated, there are companies that make custom coils that could probably give you some good guidance.
 
Sadly, there's about 0 community around me that I can find. I'm forced to come pester you guys on here. I can't even find big pottery supply shops around my area which is a bit weird. I've had contact with the folks at Bartlett and they were pretty nice about the Genesis 2.0. It's probably the system I will go for of the mini. I want to get something that will last long and be useful as I get into it more and not have to change out. Same thing as when I built the Sayber OSG grinder (love you Dan) with Kback27d instead of getting something cheaper to start off with. I knew this would be a long lasting hobby hehe

As far as calculations go, it's either single element like Hubert mentioned or a 2 zone piece. Not sure the spacing inside allows for those zones the way the coil is set up so that project might not happen for now and I'll just put an extra T.C. and temp monitor to see how the heat is distributed.


I haven't done anything yet except line up the bricks panels to have the measurements for the casing and I sure won't start connecting stuff (oh thank god my computer crashed mid message I thought I lost it ) until everything is planed out.

It does sound complicated but might as well try to learn as much as possible while building this thing. Teach a man how to fish and all that.
 
Fill out your profile with your location. We don't know where you are. Maybe there is someone who can help that you don't know about. Luckily, you have folks like Herbert here who know this stuff.
 
Well then that means that it'll take less space because I was going off ID :D a 3/8 coil is minuscule... I thought they would he around 1/2"-5/8"
 
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