# Small Heat Treat Oven



## Brian Rupnow (May 14, 2021)

This deserves a thread of it's own. I have decided that I need a small heat treat oven. I know nothing about them, but I'm learning fast. I checked out the internet, and ovens in the size range I need range from about $800 Canadian up to $3000 Canadian. I didn't want to spend that kind of money, so I posted a want add in local Buy and Sell newspapers. I got a phone call from Montreal Quebec from an Anglican minister who had some connection to potting. She had two ovens, and would sell me one for $200. plus shipping from Montreal. It shipped UPS and that cost $98. So---the oven came, I plugged it in to 110 volts and it warmed up immediately as you can see in the picture. It had no controls on it at all.  I had no idea what controls I needed, but a few helpful people on the forums stepped up and advised me on what I would need. I purchased a PID controller from Ebay, and it cost me about $230 Canadian including shipping. It consists of a plastic box about 5" x 8" x 3" deep, a pyrometer probe which extends thru the side of the oven, two 110 volt cords coming out of it, one with a male end and one with a female plug, an on/off switch, and a digital screen on it. At his time I don't know a heck of a lot more about it, but as I said, I'm learning fast.


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## Brian Rupnow (May 14, 2021)

My two car garage holds a lot of the "overflow" from my small engine hobby, and MUST have a clear space for my good wife's car. I have one place near my air compressor and old stick welder that will do for a place to mount the oven. I have angle iron harvested from 3 old bedframes (That cost $15), and will use that to make a shelf that holds my oven. So here you see the corner where my air compressor and stick welder live, and the frame of angle which will support the oven and the controller. The 3D model of a person is 67" tall, same as myself except for the white beard and pot gut.


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## Brian Rupnow (May 14, 2021)

So, if you've been keeping track, I'm now up to $543 Canadian. I don't think I am going to need anything else, but if I do I will let you know. An observation---This heat treat oven, as purchased with no controls, would be very simple and cheap for a home shop guy to build. There is really nothing to it, just some light gauge sheet metal, some fire brick, and a door. There are lots of "How to build your own heat treat oven" videos on Youtube.


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## jkimberln (May 14, 2021)

Don't put your oven controller above your oven where it can fry.  Better to locate it underneath the oven or off to the side.


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## Brian Rupnow (May 14, 2021)

jkimberln--I thought of that while I was designing the support stand. I don't have room to locate the control below or off to the right side. I could always move that 220 volt outlet mounted on the piece of plywood down another six or eight inches--that might free up space to mount the controller below the furnace.


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## clockworkcheval (May 15, 2021)

Your set-up certainly looks good! As explained in the parallel thread 'Keeping 01 free of carbon buildup while hardening' quick transport from oven to quencing bath is essential, so you may want to spend some thought of where to position your quencing bath. Our resident heat treatment engineer has explained to me that quencing slightly alloyed Silversteel in water may give a somewhat harder result. But it brings the risk of soft spots where vaporbubbles originate and the risk of cracks. So water quencing is best limited to simple shapes and under vigorous stirring. In other situations quencing in oil is preferable at a temperature of about 50 degrees Celsius. In a bath of one liter oil or more small components will only increase the quencing temperature a couple of degrees.
By the way, in full heat the topside of my oven is only a little bit hotter than handwarm. So I think that when you put a piece of steel or aluminum sheet as heatsink/-deflector under your control its position on top of the oven should not be a problem.


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## ajoeiam (May 15, 2021)

Further to clockworkcheval's note - - - - put your controller shelf a moderate distance above the oven and run a 3W computer type fan to move the warm air from above the oven to make sure that the controller is kept cool.
Low cost for purchase and in use and will minimize space requirements - - - - HTH.


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## HennieL (May 15, 2021)

Brian Rupnow said:


> I purchased a PID controller from Ebay, and it cost me about $230 Canadian including shipping. It consists of a plastic box about 5" x 8" x 3" deep, a pyrometer probe which extends thru the side of the oven, two 110 volt cords coming out of it, one with a male end and one with a female plug, an on/off switch, and a digital screen on it.


Hi Brian,
Congratulations on the oven - it's always much better if one can do one's own heat treatment.
Regarding the PID, did you get an operator's manual with it? If not, search online for the name/model number of the unit mounted in your box and download the info (if possible). PID's come in various flavours, but all of them have some capability to be programmed. In case you don't know, they work by switching "on" before the temperature that is being controlled falls to your lower required limit, and switch "off"  before reaching the upper set limit. This then evens out the lag where with a normal household oven the temperature overshoots the desired (set) temperature, and then undershoots the lower limit by only starting to warm up again when it crosses the set limit threshold (hope this is clear...). 
Most PID's (if set into the correct mode) can also "self learn" what the actual lead and lag times must be , so as to not overshoot the target temperature. The operator's manual should tell you about these matters, and how to program the unit. If you cannot find the information, please drop me a PM with your email address, and I will send you some generic information, in PDF format, that should put you on the right path.
Just to get you started, the "SV" display is your set value (the temp that you want to maintain), and the "PV" is the actual temperature of the oven. Press the sideways arrow below the displays to get into "set"  mode, and then either of the "up" or "down" arrows to adjust the flashing digit. Press the sideways arrow again to scroll through all the digits, setting each digit individually. Press the "set"  button to store the set value and start the oven. (As I said, units differ, and yours might need you to press the "set" button to start...

I agree with jkimberln that it's not ideal to have the controller directly above your oven.



> I don't think I am going to need anything else, but if I do I will let you know


You will need a quench tank and a proper quenching oil (don't use old engine oil or similar...). You will also need a tempering oven, if at all possible. One can use the main hardening oven, but it uses a lot more electricity than a small dedicated toaster oven, and it allows one to do both the hardening and the tempering operations at the same time.
An old fire extinguisher, with just the top cut off, makes a very nice quenching tank for small items, holding about 4-5 liters of oil. If you are going to heat treat larger parts then you will probably have to weld your own larger tank. I have two tanks, a 5 liter ex-extinguisher, and a much taller large diameter pipe with one end welded shut with a 2mm steel plate that also acts as it's stand - this tank holds 25 liters of oil.

Depending on the type of steel you plan to harden, your cheapest "best" quenching oil to use (if you don't want to buy actual quenching oil...) is Canola cooking oil - it is a rather quick quenching oil, and being a vegetable oil, it has a very limited vapour phase, ensuring uniform hardening. It also smells like chips when heated - a much more pleasant smell than most other oils 
And yes, clockworkcheval is correct, heat up your oil to make it cool the steel more rapidly.


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## HennieL (May 15, 2021)

Brian Rupnow said:


>


One more thing, Brian - You should place some type of baffle between the exposed heating elements and the steel you want to harden. The temperature of the element is much higher than the optimal austenitizing (heating) temperature of most steels, and will tend to create "hot spots" on the sides of your tool that is exposed to the element. This will result in grain growth and carbon loss, both unwanted. This can be something as simple as half a fire brick, or even a sacrificial sheet of steel. Well worth the added effort/cost.


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## Brian Rupnow (May 15, 2021)

Thank you Hennie L--I did get two sheets of info with my controller, but after reading it, I don't have the faintest idea what it said. A lot of gobblydegook.  Once everything is hooked up and in place, I may have to reach out to you for a a bit for help to get it set up.--Brian


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## clockworkcheval (May 15, 2021)

Two reasons for a separate tempering oven. In the first place you want to do the tempering immediately after the quencing, and your big oven will take a while - up to 30 minutes - to cool down to tempering temperature. In the second place at least my wife was not happy with the prospect to let 'my stinky oily part' simmer for an hour in her kitchen oven. A small oven capable of heating up to 200 - 220 degrees Celsius or 400 - 430 degrees Fahrenheit and with a timer up to one hour will probably set you back no more than $ 20 to $ 30.
A word of caution on the self-learning of some controllers: at one time mine teached itself to go full-out to reach the maximum temperature the oven can handle. And still went full-out when I wanted a lower temperature causing a strong overshoot in temperature.


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## clockworkcheval (May 15, 2021)

On a baffle; I found a slab of thin so-called pizzastone very useful to make all sorts of baffles and subdivisions in the oven.


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## HennieL (May 15, 2021)

Brian Rupnow said:


> Thank you Hennie L--I did get two sheets of info with my controller, but after reading it, I don't have the faintest idea what it said. A lot of gobblydegook.  Once everything is hooked up and in place, I may have to reach out to you for a a bit for help to get it set up.--Brian


My pleasure, Brian - just shout if you need help.



clockworkcheval said:


> A word of caution on the self-learning of some controllers: at one time mine teached itself to go full-out to reach the maximum temperature the oven can handle. And still went full-out when I wanted a lower temperature causing a strong overshoot in temperature.


Yup, that happens if the programmed parameters are incorrect. Best to record all the parameters (and there are a lot of them...) pre-programmed before making any adjustments to the program - these units are not called "*Proportional, Integral, and Derivative*" devices for nothing - they like Calculus


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## Asm109 (May 15, 2021)

I hope the controller you bought has an auto tune feature built in.  I have used those for controlling the temp of a heat staking tool.  Makes initial setup painless.  Turn on the auto tune and let the thing go through its motions.  Essentially it is smart enough to heat up watch the response and and set the PID gains for fast response with minimal overshoot.


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## Brian Rupnow (May 15, 2021)

I moved things around a little and located the controller below the oven. That should keep oven heat away from the controller better. If I had to, I can put some insulation in the gap between the oven and the controller.


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## Brian Rupnow (May 15, 2021)

I've had as much fun as I can stand for one day. Probably about half done on the support frame for the oven. It's been a while since I done much welding, but I do love this mig.


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## simonbirt (May 16, 2021)

interesting thread. I have just bought a Prometheus Mini Kiln Pro-1 which has a digital controller. I thought it was time to make my toolmaking a bit more precise. I have had an initial play and have had variable results thus far using silver steel (drill rod) and gauge plate (01 tool steel) the former water hardening the latter quenched in oil.

Very happy with the kiln/muffle furnace/ oven which does a great job. It is not much use for tempering as it takes ages to cool to the correct temperature, using the domestic oven pro tem.

I have tried a variety of technique raging from heating the oven to the correct temperature then placing the sample on a stainless rack and waiting for the temperature to recover and then quench. Heating the sample slowly and soaking for 1 hour per inch and something in between.

Smaller diameters up to about 3/8” have all been good and are glass hard after quenching. Above this things are not so simple, the outer part remains soft with the centre hard soft all the way through. Tried a few things including raising the temperature to 800 deg C for silver steel which according to the data sheet is at the upper end. I made a D bit 1/2” dia and this proved a challenge. 


Gauge plate seems more consistent but I have not tried any large sections as I mostly use it to make form tools for the lathe 3/8 x 3/8” or thinner and wider. 

I have ordered a set of hardness test files which should remove some of the guess work. I then plan to adopt a more scientific approach.

All in all I’m not really sure why I am doing this as I really did not have a problem hardening the stuff I need with a propane torch. Occasionally I would have distortion on long thin work.

One other observation: I think I was heating well above 780 degs with my gas touch as the colour seems brighter than what I am seeing in the oven. By the way I have a high temp thermocouple and gauge which confirms the temp of the oven within a few degrees.  

I may make a short video showing my experiments.


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## clockworkcheval (May 16, 2021)

Increasing the hardening temperature above 800 deg C seems like a good idea. Our resident metallurgy engineer advises for small oil quenching parts a hardening temperature of 830 deg C for at least 15 minutes. After that as quick as possible transfer to the quenching bath of oil at 50 deg C. Tempering soon after that at 200 deg C for something like one hour.


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## HennieL (May 16, 2021)

simonbirt said:


> I have tried a variety of technique raging from heating the oven to the correct temperature then placing the sample on a stainless rack and waiting for the temperature to recover and then quench. Heating the sample slowly and soaking for 1 hour per inch and something in between.


Ideally one should heat the steel in the oven from cold, but that only works if you have an industrial oven with an inert atmosphere, and/or a oven that does not have any "hot spots" as a result of exposed heating elements or direct flame. In practice, I pre-heat my oven to the correct temperature, and then insert the steel to be hardened. I then start my "soaking timer" once the temperature inside the oven has recovered - this normally takes 5-10 minutes, depending on the size of the item being hardened, and the actual hardening temperature required (stainless and high-alloy steels require temperatures in the range 1050°C to well over 1150°C for some types of HSS, and these take longer to recover...). Important is to ensure that you "soak" the steel for the required time at the hardening temperature - i.e. leave it at temperature in the oven/kiln for the required "soaking" time (this varies from steel type to type...)



> I have had an initial play and have had variable results thus far using silver steel (drill rod) and gauge plate (01 tool steel) the former water hardening the latter quenched in oil.
> Smaller diameters up to about 3/8” have all been good and are glass hard after quenching. Above this things are not so simple, the outer part remains soft with the center hard soft all the way through. Tried a few things including raising the temperature to 800 deg C for silver steel which according to the data sheet is at the upper end. I made a D bit 1/2” dia and this proved a challenge.
> Gauge plate seems more consistent but I have not tried any large sections as I mostly use it to make form tools for the lathe 3/8 x 3/8” or thinner and wider.


Larger pieces of steel are apt to "self temper" if you just leave them in the oil, or remove them from the oil whilst still warm (50°C - 100°C) as many people recommends one to do. I disagree with this advice. What happens is that the outside of the tool cools down rapidly whilst the inside remains much warmer (above 200°C) for some time, and this results in the interior of the part tempering the exterior whilst the interior is still hardening. Rather remove your larger parts from the oil whilst still too hot to touch, and then plunge it into water to finally cool down to air temperature. There is a very slight increased risk of the part cracking, but I've only experienced one such crack during the 10+ years that I have been doing my own heat treating.

Of course, the steel type also plays a major role in how deep one can harden a thick part - look for steels that have some manganese, molybdenum and/or chromium in the alloy - this makes for deeper hardening. O1 is excellent for larger parts - I suspect your silver steel is a plain medium carbon steel without much other alloying elements, hence the reason why it won't through-harden.


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## Gordon (May 16, 2021)

The discussion is interesting but I doubt that Brian's kiln is capable of reaching the temperatures needed for heat treating tool steel. I think that his goal is to merely anneal cast iron rings and that is 1100 F. I have a small ceramic kiln and I doubt that is is capable of reaching the temperatures required for tool steel. I have never tried to push it to that type of temperature so I may be wrong. An industrial heat treat furnace is an entirely different animal  than a ceramic kiln.


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## Brian Rupnow (May 16, 2021)

The frame is completely fitted and tack welded, and the oven and control are in place for test fit. The old red stick welder fits right in where it always sat, but I have it removed right now because I had to get down where it was to put some woodscrews into the framing on that wall. I'm going to move that air hose reel about three inches to the right, and all the stuff that was hanging on that wall is going to hang on a different wall. I'm quite happy with this. I will now put the oven and controller back in the house, take down the frame, and finish welding all the joints.


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## MJOSPINA (May 16, 2021)

Nice project, Brian. Maybe the questions is what is the highest temperature you can reach with the oven


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## HennieL (May 16, 2021)

Gordon said:


> The discussion is interesting but I doubt that Brian's kiln is capable of reaching the temperatures needed for heat treating tool steel. I think that his goal is to merely anneal cast iron rings and that is 1100 F.


Well Gordon, O1 is tool steel, and it's only heated to around 800°C - 820°C... The point of mentioning high alloy stainless and high speed tool steels' heats was not that Brian would necessarily need (or want) to harden these steels, but rather to point out that these high temperatures take longer to equalize back to the required temperature once one adds the part to be hardened into the pre-heated oven/kiln, due to the higher target temperature required.

Not that it is very difficult to heat the martensitic stainless steels - I do it all the time using a small electric HT oven (not an industrial oven), and I dare say that Brian's pottery oven can heat just as high. Now heating HSS is a different kettle of fish - the 1150°C (2100°F) really pushes my oven to the limit, but even so, I have very successfully (and more than once...) hardened Bohler S705 (equivalent to AISI M41) to an after temper hardness of 65.5 Rockwell C in my little oven, so it can be done. Here is one of my wood-turning chisels that I made with this steel:


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## Gordon (May 16, 2021)

I guess that I just never thought about using my kiln for that. I bought it to anneal cast iron rings and that is all that I have ever used it for. I have made quite a few parts from W-1 but I used the torch to heat them to carrot color, quenched them in water and then tempered them in a toaster oven. I heat rings to 1100 F and W-1 requires 1425 to 1500 F so I am sure that my kiln is capable of that. Looks like I have something new to try. Too soon old and too late smart.

Gordon


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## ajoeiam (May 17, 2021)

HennieL said:


> snip
> Here is one of my wood-turning chisels that I made with this steel:



Hmmmmmm - - - - I would be quite curious as to the process you followed to make this. 
A description of some kind please?


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## HennieL (May 17, 2021)

ajoeiam said:


> Hmmmmmm - - - - I would be quite curious as to the process you followed to make this.
> A description of some kind please?


 I don't think we should hijack Brian's threat any more than we already have (apologies Brian...). I will post a new thread on this - now should it be under "Tools" or under "Metals"... hmm, rather under "Tools", I think...
I will have to just gather my info (I think I took a few photos at the time, but will have to search for them)... Will probably only post this evening (local time)


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## HennieL (May 17, 2021)

HennieL said:


> I will post a new thread on this - now should it be under "Tools" or under "Metals"... hmm, rather under "Tools", I think...



OK ajoeiam, just for you 
Heat treating high alloy and high speed steel tools


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## awake (May 17, 2021)

Hennie, some very helpful information - I look forward to reading the new thread as well.


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## willray (May 18, 2021)

HennieL said:


> ... Now heating HSS is a different kettle of fish - the 1150°C (2100°F) really pushes my oven to the limit, but even so, I have very successfully (and more than once...) hardened Bohler S705 (equivalent to AISI M41) to an after temper hardness of 65.5 Rockwell C in my little oven, so it can be done.



--edit--
(I notice, HennieL has responded to my plea even as I typed!)
--end edit--

Ooh, ohh - someone who will admit to successfully heat-treating HSS, rather than intoning the gospel homile "it's complicated, and can't be done"!

Pray tell - could you give some ballpark starting advice or pointers to guidance that does not require a lifetime's investment in learning the holy language spoken in the industrial HSS inner sanctum?

I ask because I have something well north of $10K of decent-quality HSS cutting tools - primarily Chicago Latrobe, Morse and Cleveland Twist Drill - that I successfully annealed by passaging them through my shop fire.   Yes, it got that hot - my shop fire puddled cast-iron tools, and turned barrels of silicon flour into glass plugs.   If I can salvage mild-steel, or even just woodworking capability out of even a small fraction of the tooling, I'll be thousands of dollars ahead of buying it all again.

I realize that I don't know most of the alloys, and the random time/temperature soak to which everything was subjected makes any attempt to be precise about moves from their current state into a joke.  I can live with that - even a small percentage of successes is better than nothing.  20x my insurance payout won't come close to making me whole, so I'll take anything I can get.


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## HennieL (May 18, 2021)

willray said:


> Pray tell - could you give some ballpark starting advice or pointers to guidance that does not require a lifetime's investment in learning the holy language spoken in the industrial HSS inner sanctum?
> 
> I ask because I have something well north of $10K of decent-quality HSS cutting tools - primarily Chicago Latrobe, Morse and Cleveland Twist Drill - that I successfully annealed by passaging them through my shop fire.   Yes, it got that hot - my shop fire puddled cast-iron tools, and turned barrels of silicon flour into glass plugs.   If I can salvage mild-steel, or even just woodworking capability out of even a small fraction of the tooling, I'll be thousands of dollars ahead of buying it all again.


Willray, please see the link in my earlier reply to ajoeiam - I started a new thread on this topis, so as to not further hijack Brian's thread. Won't you just repeat your questions there (just to keep the thread neat...), and I will respond as best I can.

Hennie


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## willray (May 18, 2021)

HennieL said:


> Willray, please see the link in my earlier reply to ajoeiam - I started a new thread on this topis, so as to not further hijack Brian's thread. Won't you just repeat your questions there (just to keep the thread neat...), and I will respond as best I can.



Absolutely - I had started my post to ask last night, but didn't get around to clicking "post" until I got to the office this morning, and then discovered that in the mean time, you'd already granted my half-written wish    No desire to hijack Brian's thread!


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## Brian Rupnow (May 18, 2021)

The frame that supports the heat treat oven is finished. It is fully welded and even painted. The old Lincoln A.C. welder even got a new handle out of the deal.--It had a handle on it to move it around years ago, but for some reason I had cut  the handle off, and I can't remember why. The next stage of this game is going to involve figuring out the control for the oven. It is intimidating because it has to be programed, and I haven't got the faintest idea how to do that. I have two pages of instructions that came with the controller, and I think they are written in ancient Greek or one of the "dead languages".


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## HennieL (May 18, 2021)

Brian Rupnow said:


> The next stage of this game is going to involve figuring out the control for the oven. It is intimidating because it has to be programed, and I haven't got the faintest idea how to do that. I have two pages of instructions that came with the controller, and I think they are written in ancient Greek or one of the "dead languages".


Not in official Chinglish?

Brian, as posted earlier, just switch it on, and play around with changing the SV (set value). If this works, you are well on your way to mastering it.
Please send me (or just post here...) the manufacturer's name and/or model number of the PID itself (not the whole controller) - this should be somewhere on the PID - or just post a close-up photo of the unit. If we can identify the make and model number, we should be able to download the instruction manual, and then it should be easy to go on from there.


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## awake (May 18, 2021)

Brian Rupnow said:


> I have two pages of instructions that came with the controller, and I think they are written in ancient Greek or one of the "dead languages"



γεγραμμένην ἐν τῇ Ἑλληνικῇ γλώσσῃ τῇ κοινῇ ἐστὶν; αὐτὴv καὶ γράψαι καὶ εἰπεῖν δύναμαι. σοι βοηθῆσαι θέλω.


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## Gordon (May 18, 2021)

awake said:


> γεγραμμένην ἐν τῇ Ἑλληνικῇ γλώσσῃ τῇ κοινῇ ἐστὶν; αὐτὴv καὶ γράψαι καὶ εἰπεῖν δύναμαι. σοι βοηθῆσαι θέλω.


That is what my controller says also.


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## awake (May 18, 2021)

Gordon said:


> That is what my controller says also.


Uh-oh, that's not good. It translates to an offer to help ... without actually helping at all!


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## Gordon (May 18, 2021)

awake said:


> Uh-oh, that's not good. It translates to an offer to help ... without actually helping at all!


Actually I did manage to understand it enough to get the controller to work along with some trial and error. I was only interested in getting the controller to attain a temperature so cycles and different temperatures were not necessary. I wanted to get to x° F and I have a clock which I could watch to turn it off after the required time period.


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## awake (May 18, 2021)

Gordon said:


> Actually I did manage to understand it enough to get the controller to work along with some trial and error. I was only interested in getting the controller to attain a temperature so cycles and different temperatures were not necessary. I wanted to get to x° F and I have a clock which I could watch to turn it off after the required time period.


Ah, I see a potential problem - the ancient Greeks did not use Fahrenheit, so this may be throwing off your settings ...


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## HennieL (May 18, 2021)




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## Gordon (May 18, 2021)

The sun dial is not as accurate as I would like to be either.


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## awake (May 18, 2021)

Gordon said:


> The sun dial is not as accurate as I would like to be either.


Yes, good point. The glow from the furnace can cast a shadow and cause a false reading. The ancient Greeks did have water clocks (? I think? if I recall correctly?) but that may not be a good choice around heat and electricity either.


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## Brian Rupnow (May 18, 2021)

I scanned my instructions and they all came up as .pdf files and I can't upload them. so, being Mr. Resourceful, I took pictures of them with my camera because it saves them as .jpeg and I can post them. I will be very grateful for any help.---Brian


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## HennieL (May 18, 2021)

OK Brian, I see it's called a "DTXG" - Google gave me access to sites where I downloaded the same instruction manual, and a second Word document with some more info. Please send me your email address (PM me...) and I will forward them to you.

It's getting quite late here in my nick of the woods, and I must have an early start tomorrow morning, but I will try to read up on the documents through the day tomorrow, and see if I can help you tomorrow evening (SA time - say an hours before the time of this post...).

One quick thing that I can note now, is that this unit does differ slightly in setting the required temperature - according to the operator's manual one must push the "Set" button for a short period (not more than probably one second) in order to enter the "SV setting mode". Then, it's as I suggested earlier - push the sideways arrow to jump between the various digits (i.e. the "ones", "tens" "hundreds" and the "thousands". On each of these digits, push either the "up" or "down" arrows to change that digit's value, and then push the sideways arrow again to move to the next digit. Once your temperature is set, push the "SET" button again to store that value and start the oven.
Don't push the "SET" button for more than a short push, though - keeping it pushed for more than 3 seconds will cause the unit to enter it's "Program" mode, and we don't want to go there yet. If it does enter the program mode, don't panic, though - just leave it be (do nothing) and it will revert back to it's normal mode in about 10 seconds or so.
Hope is is of some help in the meantime...

Hennie


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## Brian Rupnow (May 18, 2021)

Hennie---My email is [email protected]  Thank you.---Brian


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## Brian Rupnow (May 18, 2021)

If you look at the lower left corner of the frame I built, down by the air compressor tank, there are two screws going into the "baseboard". My knees have got so bad that there was just no way to get down on my knees in that corner to put the screws in.  I have "gell" kneepads, but my knees are basically "bone on bone" now, and it just hurts to much too get down on them. Damn, getting old isn't much fun. Anyways, our 42 year old son came over for supper tonight and brought his battery powered screwdriver and put the two screws in for me. I still have to grind away a little bit of weld inside the oven holding bracket so the oven sets level, and then it will be on to the oven and controller.


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## Brian Rupnow (May 19, 2021)

My heat treat oven has a round hole in the door (see post #8 for picture). I assume that is where the temperature testing probe connects to tell the controller how hot it is inside. that seems to me to be very inconvenient. Can I put a new hole in thru the side of the oven and mount the probe permanently in the side? What can I use to plug the hole in the door?---Brian


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## HennieL (May 19, 2021)

Brian Rupnow said:


> My heat treat oven has a round hole in the door (see post #8 for picture). I assume that is where the temperature testing probe connects to tell the controller how hot it is inside. that seems to me to be very inconvenient. Can I put a new hole in thru the side of the oven and mount the probe permanently in the side? What can I use to plug the hole in the door?---Brian


I don't see any reason why you would want a probe through the door... I would install it through the back of the oven (presuming there are no heating elements in the back). The refractory material might be brittle and crack, but hopefully if you just go slowly and use a concrete bit you could do it without serious problems.

Does your probe have a sheath? Probes also need to be protected from oxidation at high heat, and it is normal to install the probe inside a ceramic or stainless steel sheath that screws air-tight onto the probe. these sheaths normally come with some kind of mounting bracket, and that would dictate the position that is must be mounted in/on your oven - see below:


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## Gordon (May 19, 2021)

My oven has the probe through the top rear of the oven. The refractory material is pretty soft and easy to drill. Just go slow and make sure that it is not through one of the heater elements. If you go through the hole in the front you will be flexing the leads every time you open the door and they will soon break.


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## Brian Rupnow (May 19, 2021)

The heat treat oven is in it's final home position. I drilled thru the side of the oven near the top, for the thermocouple, not interfering with the heating coils, about  4" in from the front (the oven is 8 1/2" deep.). I have power to the controller and the oven is heating up and the digital display on the controller is lit up. I have to put a new 3 wire lead on the oven, as it only had a two wire lead and plug on the cord, with no ground. I went down town this morning trying to find a length of 3 wire heat resistant cord, but all the businesses are shut down for covid. I'm happy with what I have here, and hopefully will be even happier when I get the controller figured out. This oven has the cheesiest hinges ever, I think they are made form #20 gauge steel, so I will fabricate new hinges for each side of the door.


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## HennieL (May 19, 2021)

Well done Brian 
Have you tried to adjust the PID as I suggested in post #43? Curious to know if it works, and shuts off around the 100° setting that is currently showing on the PID (the green SV reading).


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## BaronJ (May 19, 2021)

Brian,  that hole in the door is supposed to be a viewing port and should have a high temperature glass window in there.  If you don't want it put a plate over the hole and stuff some insulation in it.


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## Brian Rupnow (May 19, 2021)

HennieL  I haven't tried anything on the controller yet. Saving that exercise for tomorrow. Tomorrow I will take a run at the controller and see about making better hinges for the oven door.---Brian


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## willray (May 20, 2021)

BaronJ said:


> That hole in the door is supposed to be a viewing port and should have a high temperature glass window in there.  If you don't want it put a plate over the hole and stuff some insulation in it.



Not to be too contrary, but I don't think I've seen such a thing on a kiln.  All of the kilns I've worked with (admittedly, only 6 or so) have either little (usually cast iron) doors pivoted from a simple screw above the peephole, or, they use kiln plugs:

< Skutt Peephole Plugs | BLICK Art Materials >


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## willray (May 20, 2021)

Regarding your thermocouple installation:

Of course you know heat rises - there's only so much you can do about thermocouple position in a small chamber like that, but you might be surprised at how much difference there can be between the top and the bottom of the chamber.  Don't be surprised if you need to make some tweaks to temperature controller settings to produce "correct" temperature set point results.

Another possible cause of consternation (or not, if your controller is actually designed for this) - most of the heat transfer in your oven will be radiative, and your exposed thermocouple will experience exactly the same phenomenon that you observe when you discover that the black fender on your car is blistering-hot to the touch on a sunny day, even though the air may be cool, or is chilly-cold to the touch on a cloudless balmy night.

The thermocouple sheath/thermowell device that HennieL shows is not simply there to protect the thermocouple from the atmosphere, but also to shade it so that it responds more accurately to the kiln's temperature rather than to the elements' temperature.   If your controller expects a shielded thermocouple, you may have to play with your controller a bit to get it to behave well.

Neither are show-stoppers by any stretch of the imagination - just things to keep in mind if things don't seem to go quite by-the-book when you start it up.

Best of luck!
Will


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## Brian Rupnow (May 20, 2021)

After what seemed to be an incredible lot of faffing about, I have the oven controller operating, holding the oven at a constant 1100 degrees Fahrenheit. I may want to tighten up the parameters, (its cutting off power at 1130 degrees and restoring power at 1020 degrees. I will search about in my instructions and see if there is a way to do that.


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## HennieL (May 20, 2021)

Congrats, Brian - now you're getting there.
I suggest you now run the "Auto tuning" function of your PID. The below is an extract from the manual that I emailed to you, and lists the steps. The two documents that I sent to you differ a bit - typical of the Chinese documentation, and I'm not 100% sure which one would be fully applicable to your unit, but I suggest you try the following:

Start with your oven cold the the "SV" value set to your 1100°F
Press the "Set" button for at least 3 seconds - the unit will then enter it's "programming" mode.
 Following the program steps in the image posted below, repeatedly press and release the "Set" button, checking to see if the menu follow that on the left hand side of the image - starting with "AL 1".
Keep on pressing and releasing the "Set" button until you reach the "Auto tuning switch" depicted with either "Aru" or "At" on the display. According to the manual this should be the 3rd push of the button, but depending on the unit's security settings it could perhaps be only after the 10th button push.
Don't push any other buttons except for the "Set" button until you reach the "Auto tune" function, else you might inadvertently change something else.
When you reach the "Auto tune" function, press the sideways arrow button once to enter this function.
Check the display, and confirm that the value now shows either "0" or "off". Press either the up or down arrow to change this value to either "1" or "on".
Press the set button to exit this function.
If the "Auto tune" led does not light up and the oven does not switch on, press the "Set" button a second time, keeping it pressed for at least 3 seconds - it should then start.
Leave the oven to cycle on and off for some time (could take hours...) until it finally switches off on it's own - the auto tune function would then have switched off, and your PID should now be "tuned" for your oven.
If everything went well, it should now have less over- and under-shoot.





I really hope this works for you - unfortunately, not being able to look at your PID while you're running through the program steps, there is a (slight) risk that it might not respond as I'm used to my PID's responding, but even if it does not auto tune correctly, you will still be able to change each individual parameter back to it's factory setting, so no great risk here...

Good luck


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## Brian Rupnow (May 20, 2021)

I didn't do any more messing around with the controller today. I still have to learn more about it and I've seen that I can get the oven to go to 1100 degrees F and hold it there, which was my biggest question. This oven had the poorest hinge plates on it that I have ever seen. They are only .025" thick material and were bent all to heck. I whittled out some new hinge plates this afternoon from 3/16" aluminum and tomorrow I will concentrate on getting the "door" to fit better and install the new hinge plates.


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## dsage (May 21, 2021)

If I can make another suggestion.
The display might be showing 1100deg but can you prove it is??
Pre-heat the oven to one of the temperatures that produce the well known tempering colours.
For instance 282deg C (540def F).
Put a thin piece of very clean steel in the oven and let it soak for an hour or more (depending on the metal thickness). For the temperature mentioned the steel should have turned purple.
You can google the tempering colours. They are very close in temperature and accurate. So you can get your oven tuned very close with those. It will probably come down to the best placement of the thermocouple to accurately sense the real internal temperature.
Don't forget you need to allow a long time at the beginning of a session for the bricks heat to stabilize.


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## clockworkcheval (May 21, 2021)

With respect, one of my main drivers to buy an oven is that I'm not really able to tell temperature by colour. 'Halfway between cherry-red and tomato-red as observed in an old dark and smoky smithy' is way beyond my skills. It is remarkable therefore to see the suggestion to use colours to check the temperature of an oven. The only comparative check I do once in a while is to put a piece of aluminium in the oven and set the temperature just over its melting point. If it then melts I consider the temperature indication to be OK.


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## willray (May 21, 2021)

clockworkcheval said:


> With respect, one of my main drivers to buy an oven is that I'm not really able to tell temperature by colour. 'Halfway between cherry-red and tomato-red as observed in an old dark and smoky smithy' is way beyond my skills. It is remarkable therefore to see the suggestion to use colours to check the temperature of an oven.



In all fairness, dsage's suggestion was to use the tempering colors rather than the black-body radiation colors as a cross-check.

In addition to tempering colors, and going up to temperatures considerably above the canonical steel tempering colors, there are these neat temperature-check crayons available:

Tempilstik

A handful of these that span your desired temperature range, and you can scribble on a piece of steel and then simply look to see which ones melted and which stayed "crayon gritty", to learn what temperature different parts of the kiln achieved.

... and also, do be aware of that radiative heating issue - a surface that "sees" the elements will heat much faster, and be a lot hotter, than a surface that is shaded from the elements.  This makes getting some geometries all to the same (similar) temperature, a real challenge.  Sometimes you need to intentionally put "shade walls" up on the sides of your part so that none of it can directly see the elements...


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## Brian Rupnow (May 21, 2021)

This morning I installed the new hinge plates on the oven. The door fits much better with no gaps now. I managed to turn on the Auto-tune function and with the temperature set at 1110 degrees the oven shuts off at 1112 and turns back on at 1108. I'm very happy with that.---and for now, that is all the programming I need. in future I may want to do other things, which may mean that I have to learn more functions, but for now, I'm fine. This essentially ends my work on the oven. Thanks so much for the help you fellows gave me. I would have been lost without some guidance from forum members.---Brian Rupnow


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## dsage (May 21, 2021)

clockworkcheval said:


> With respect, one of my main drivers to buy an oven is that I'm not really able to tell temperature by colour. 'Halfway between cherry-red and tomato-red as observed in an old dark and smoky smithy' is way beyond my skills. It is remarkable therefore to see the suggestion to use colours to check the temperature of an oven. The only comparative check I do once in a while is to put a piece of aluminium in the oven and set the temperature just over its melting point. If it then melts I consider the temperature indication to be OK.



It was meant as a verification that the controller is indicating / operating properly. Especially considering Brian arbitrarily inserted the thermocouple himself. When you can confirm the reading then you can rely on it and not use the colours. With  respect. The "melting point of aluminum" is probably quite variable depending on alloy and from welding experience is hard to determine by looking at it.
I'm not talking about glowing pieces of metal - yes difficult to tell. Rather the metal surface turns a colour and they are easy to differentiate. There are many colour charts available on the internet. For instance purple and blue are easy to differentiate and the difference in temperature is small.
Again, just as a verification of the oven operation until it can be trusted. If it's accurate at lower temps then it can probably be trusted at higher temps.
If the temperature is important then it is important to be sure your equipment is measuring it accurately. It's not wise to just blindly accept a digital readout.
The temp sticks are a good idea too. But only if you have them at hand.


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## HennieL (May 21, 2021)

Brian Rupnow said:


> I managed to turn on the Auto-tune function and with the temperature set at 1110 degrees the oven shuts off at 1112 and turns back on at 1108. I'm very happy with that.---and for now, that is all the programming I need... This essentially ends my work on the oven. Thanks so much for the help you fellows gave me. I would have been lost without some guidance from forum members.---Brian Rupnow


That's good news, Brian - glad I could help a bit 
Last suggestion - run the auto tune once a year - temperature probes age worse than humans, and it's just good maintenance to adjust for changes...


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## Gordon (May 22, 2021)

Thanks to Brian's experience I tried to heat treat some parts made from W1 drill rod. In the past I just heated up the part with the torch and quenched it in water. This time I put the part in my kiln at 1450° for one hour and then quenched it and put it in my toaster oven. I just had never even thought about using the kiln. Everything went well except that I screwed up something on my controller setting and had to go back and reset some things. 

I am sure that this method is more precise but it certainly is quicker to use the torch.

Gordon


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## HennieL (May 22, 2021)

Gordon said:


> Thanks to Brian's experience I tried to heat treat some parts made from W1 drill rod. In the past I just heated up the part with the torch and quenched it in water. This time I put the part in my kiln at 1450° for one hour and then quenched it and put it in my toaster oven.


Congratulations, Gordon - welcome to the club 
If I may comment on this - W1 only has a very small % of alloying elements, and I would expect that it would only be necessary to soak this steel for a short time - It's never a good thing to keep any steel heated for longer than is necessary, as this contributes significantly to grain growth.
I don't normally work with this steel, but a Google search linked me to the Hudson tool steel corporation that recommends a 30 minute soak per 1" thickness of part.


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## Gordon (May 22, 2021)

HennieL said:


> Congratulations, Gordon - welcome to the club
> If I may comment on this - W1 only has a very small % of alloying elements, and I would expect that it would only be necessary to soak this steel for a short time - It's never a good thing to keep any steel heated for longer than is necessary, as this contributes significantly to grain growth.
> I don't normally work with this steel, but a Google search linked me to the Hudson tool steel corporation that recommends a 30 minute soak per 1" thickness of part.





HennieL said:


> Congratulations, Gordon - welcome to the club
> If I may comment on this - W1 only has a very small % of alloying elements, and I would expect that it would only be necessary to soak this steel for a short time - It's never a good thing to keep any steel heated for longer than is necessary, as this contributes significantly to grain growth.
> I don't normally work with this steel, but a Google search linked me to the Hudson tool steel corporation that recommends a 30 minute soak per 1" thickness of part.


OK thanks. I was not aware that too much time could be a problem. I also found the30 minute time but did not realize that more could be problem. My piece was1" dia x3/4 lg so30 minutes would have been fine. Fortunately the piece is not critical. Just need wear resistance. Next time the parts may be more critical.


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