New Temper oven

Gliden07

Gliden07

Well-Known Member
Well folks I cant afford a real H/T oven being laid off. So I picked this up at a tag sale for 15 bucks. Got a PID control off of Amazon, had some leftover KAO Wool to insulate it, I'll have a Tempering oven for less than 50 bucks! Hope if works decent (at least till I'm employed and can save the money for a real oven?)? I did have to order some Hi Temp wire and a heat sink for SSR. Left the timer on oven it was dead on. Gonna mount a fuse in the center hole for some protection. Fun little project! 20191007_161755.jpg20191007_161814.jpg
 
Interested in hearing how this works out, hopefully ok as I am erring doing the same for my stabilising oven, there is a thread on here I started.
 
Gliden07 said:
Well folks I cant afford a real H/T oven being laid off. So I picked this up at a tag sale for 15 bucks. Got a PID control off of Amazon, had some leftover KAO Wool to insulate it, I'll have a Tempering oven for less than 50 bucks! Hope if works decent (at least till I'm employed and can save the money for a real oven?)? I did have to order some Hi Temp wire and a heat sink for SSR. Left the timer on oven it was dead on. Gonna mount a fuse in the center hole for some protection. Fun little project! View attachment 70378View attachment 70379
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You do some interesting projects and always get a deal. I’m jealous.
 
opaul said:
You do some interesting projects and always get a deal. I’m jealous.
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Just have to live in my Budget. To do that sometimes I need to think outside of the box!! LOL!! Seriously I'm starting to think I may build a H/T oven if this works just won't have the fancy controls. But it won't really matter because I never leave when heat treating. Been doing a little reserch on the oven think the hardest thing is going to be the heating coil??
 
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I've been toying with the same idea off and on for a while. Though for now it will be the kitchen oven for me. However I will be following your build with interest.
 
Gliden07 said:
Just have to live in my Budget. To do that sometimes I need to think outside of the box!! LOL!! Seriously I'm starting to think I may build a H/T oven if this works just won't have the fancy controls. But it won't really matter because I never leave when heat treating. Been doing a little reserch on the oven think the hardest thing is going to be the heating coil??
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Saw a video of a guy making the coil for one, I think he used a SS wire but can’t remember, it was YouTube so...
 
As long as you test. Record and repeate everything else matters far less. Some would have us believe we need to drop a five figure sum to make great knives.
Funny but some really fantastic blades where made before we even had electric available
The guy that taught me in his final years was trained in those days and still remains the most skillful I have ever met.
 
For normal tempering below 400F (maybe 500F with added insulation) your oven will work as well as anything you can buy. I use a PID controlled toaster oven that controls temp ±1°F with no problem. How can you do better than that? A couple of comments on your build.

1. Be sure to use a good heat sink on the SSR, and keep heatsink in good airflow for cooling. That toaster oven is going to pull some current and create lots of heat on SSR. Did you order a 40 amp SSR? I've blown a couple of 25 amp SSRs due to excessive heat build up.

2. With the PID mounted where it's at, be sure to place plenty of insulation between hot oven and PID. If possible it would be good to have small fan mounted to blow air over PID for cooling. Perhaps extra ventilation holes in case for better airflow?

3. An old firebrick laying on bottom rack does a good job of adding mass to oven allowing a tad better heat control. I mounted the TC probe from rear of oven so tip of TC would extend into oven and be real close to center of blades in oven. Remember, only the tip of TC probe reads temperature.

About the only limitation of a PID controlled toaster oven I've found is size of blades that will fit.
 
KenH said:
For normal tempering below 400F (maybe 500F with added insulation) your oven will work as well as anything you can buy. I use a PID controlled toaster oven that controls temp ±1°F with no problem. How can you do better than that? A couple of comments on your build.

1. Be sure to use a good heat sink on the SSR, and keep heatsink in good airflow for cooling. That toaster oven is going to pull some current and create lots of heat on SSR. Did you order a 40 amp SSR? I've blown a couple of 25 amp SSRs due to excessive heat build up.

2. With the PID mounted where it's at, be sure to place plenty of insulation between hot oven and PID. If possible it would be good to have small fan mounted to blow air over PID for cooling. Perhaps extra ventilation holes in case for better airflow?

3. An old firebrick laying on bottom rack does a good job of adding mass to oven allowing a tad better heat control. I mounted the TC probe from rear of oven so tip of TC would extend into oven and be real close to center of blades in oven. Remember, only the tip of TC probe reads temperature.

About the only limitation of a PID controlled toaster oven I've found is size of blades that will fit.
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Heat sink is already on the way. I have a 25 amp SSR. Thought the 25A was gonna be enough never considered the extra heat? If it smokes I'll put in a 40A. Your right that toaster is rated for 1500W so its gonna almost max out the 15A circuit (dependent on a 10% or 20% duty cycle). I plan on 1/2" insulation on top, left side and bottom of toaster (so case will fit). The right side and back wall are getting 1". The other thing is if this works the way I think it will, even after i get or build a H/T oven it will still be GREAT to temper after hardening as there will be little to no downtime from H/T to temper!
 
Wiring done, just have to cut a couple pieces of insulation and get a little hardware for the Heat sink to attach it to the chassis, a fuse or 2 and have to put the thermal paste on it too. And need to test. All the wiring checks out but until I run it and get it to a set temp I wont know? Keeping my fingers crossed!!
 

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That looks good - gonna make a really clean neat installation. One comment - the heatsink is going to get pretty darn warm there. I've got a tad larger heatsink and it's in the open air well away from oven itself and it gets pretty warm.... actually past warm, bordering on hot. While it won't burn your hand, it is uncomfortable to hold. Where you heatsink is mounted it will get even hotter. I mounted a small 12vdc fan (wanted a 120vac fan but only had a 12 vdc fan on hand) to blow air across heatsink and it really makes a difference. Now it's almost cool. Heat will shorten the life of the SSR pretty quick.

To run the 12vdc fan I took a small cell phone charger (an old one that was 12vdc output), and wired the plug to the 120vac portion, then the 12vdc output of charger to fan. I added a SPST switch to turn fan ON/OFF because my PID stays plugged in 99% of time to display room temp at that end of room.

Later
 
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So here is the first test of oven. The PID is awesome held temp within 1 Deg, ran till it stabilized then bumped to 100 Deg again within 1 deg. I ordered another PID control that has a 40A SSR gonna put that SSR in prior to buttoning oven up. Debating on putting the Kao-Wool in the base and out back on the oven. I may build a H/T oven (over the Winter). I have been looking into wrapping coils for it out of 16ga Kanthal wire. Not sure how long the finished coil should be to fill the space I'm looking to heat though. I figured out the math for the wattage I want (1.5KW @ 120V) but there seems to be little info on the web as to how far you can stretch the finished coils. Almost there!!
 
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That's a darn good price on a PID, SSR, & TC for sure. Even the 75Amp SSR kit is only $20! I'd like it MUCH better if it was F as well as C.

I use a 4" TC so the temperature sensing tip is inside the oven a bit more closer to the blades. Something like this one: https://www.ebay.com/itm/172282254172? at $5.50 each shipped. That is one good looking setup.
 
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KenH said:
That's a darn good price on a PID, SSR, & TC for sure. Even the 75Amp SSR kit is only $20! I'd like it MUCH better if it was F as well as C.

I use a 4" TC so the temperature sensing tip is inside the oven a bit more closer to the blades. Something like this one: https://www.ebay.com/itm/172282254172? at $5.50 each shipped. That is one good looking setup.
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I was worried about that too, I'm sure it wouldn't hurt to get it closer to the center though. I checked it with an electronic thermometer with 2 thermo couple inputs. I put one on each side of the oven rack centering the 2 wire thermocouples(front to back), after stabilizing the temp in the oven for about 20 minutes I checked the thermometer. It only varied briefly 1 Degree C or less from side to side, according to the thermometer. 15708080453178923421668969101692.jpg

This is the thermometer I have. What I do know is 1) It has to be a more stable environment than a standard toaster oven, 2) GF cant get on me about doing it in the oven any more! LOL!!

PS Inkbird makes a kit that is C or F but the cost that includes a heatsink is 32 to 39 Dollars depending on relay rating!
 
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