So heres my big issue guys. I am trying to temper these knifes after heat treat, but the wife wont let me use the oven, I dont have the money to build or buy one of the fancy knife ones, and the toaster oven I bought for this is fluctuating about 50 degrees up then down and then up and down etc. So my question is, what are my options? And is the temper fluctuating that big of a deal if im not going for a certain hardness? Thanks!
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Fluctuating Temps when tempering
- Thread starter remfallen
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DanF
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50 degree fluctuation will affect your temper.
You can maximize your toaster oven with a few not-too-expensive improvements to it (it’s mentioned a lot here in many threads).
I’d link some but I suck at google-foo, lol.
You can maximize your toaster oven with a few not-too-expensive improvements to it (it’s mentioned a lot here in many threads).
I’d link some but I suck at google-foo, lol.
How does it affect the temper?
Stuart Davenport Knives
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If your target hardness is say, 61HRC, a swing up 50° past that target temp could quite possibly lower your intended target hardness by a couple of points, depending on alloy and a few other variables.
I don't know why your wife won't let you use the kitchen oven. It's not like it's going to hurt anything. Just make sure you've cleaned off any oil that might "cause a stink", no pun intended.
I have a huge stone cooking thingy in the kitchen oven, and it holds a target temp quite well due to that heat sink. You could try something akin to that in your toaster oven if a talk with the boss lady doesn't pan out.
I don't know why your wife won't let you use the kitchen oven. It's not like it's going to hurt anything. Just make sure you've cleaned off any oil that might "cause a stink", no pun intended.
I have a huge stone cooking thingy in the kitchen oven, and it holds a target temp quite well due to that heat sink. You could try something akin to that in your toaster oven if a talk with the boss lady doesn't pan out.
Stacy E. Apelt - Bladesmith
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In an effort to help those who are challenged by trying to connect a PID and its associated circuitry to a device, I will give the procedure and setup to run a toaster oven as a tempering oven. The same hookup can run a variety of things (solenoid valve on a forge, salt pot, BBQ smoker, kiln, etc.), with the appropriate thermocouple and SSR. If you only want it to read temperature, you just use the thermocouple as a thermometer.
Some components can be found in thrift stores, other from online suppliers, and most everything can be purchased on Amazon or Ebay. Search for PID, Thermocouple K, SSR, Thermocouple plug connector, 120V cooling fan.
The Oven:
Any manual control toaster oven will do fine. You don't want a digital control oven. One of the old twist-dial types for a few dollars from a thrift store will be perfect. It only needs to be able to set the oven on HIGH or ON. You are going to permanently set it on the highest setting. It needs nothing modified beyond a small hole drilled to allow the thermocouple to stick inside. Some folks wrap a blanket of insulation around the oven to get a little more efficiency. That is a good idea but use the proper insulation. You want a jacket insulation blanket, which controls the loose fibers, like a water heater wrap from the hardware or plumbing shop. Wrap the entire toaster, including the back, and tape the jacket with duct tape. Leave a flap to drop over the front door. This will greatly help the oven regulate temperature and hold a somewhat higher temperature.
The PID:
Most cheap PID controllers are pretty much the same. You want 120VAC input and the ability to take a type K thermocouple.
They often come as a package deal with the PID, SSR, heat sink, Thermocouple, and wires.
Amazon search - PID Temperature Controller Set, PID Temperature Controllers Thermostat Regulator, SSR 40DA Solid State Relay AC 100 to 240V, White Heat Sink and K Type Sensor Thermocouple
The Thermocouple:
The Thermocouple that they often give you with those controllers is pretty useless for most of our purposes, so you will likely need a new one. The temperature range needs to match the desired use. If it is going into an electric toaster oven, it just needs to be a type K that is long enough and rated around 1000F. (BTW, there is a + and - wire, make sure you hook them up right or the display will read wrong.) If your TC has a plug-in probe cord. get a corresponding K-type socket to connect to the PID.
You don't want the ceramic coated TCs for a tempering oven. Just a metal clad probe.
Amazon search - 3M K-Type Thermocouple 100mm Sensor Probe Temperature From -100°C to 1250°C
How it works:
The SSR is actuated by the DC output voltage from the SSR control circuit on the PID.
The SSR can control 48-480VAC circuits. The SSR amperage rating needs to be enough to run the device being controlled, plus a bit. Most folks just use a 40-Amp SSR. You will need a heat sink on the SSR to keep it from burning out (they only will take 3-5 amps otherwise). A small fan, like from a computer, should be used to cool the heat sink.
A 10-foot 120VAC 15-Amp rated 14-gauge extension cord. It will be cut into four pieces - 3-feet with female socket; 5-feet with the male plug; two 1-foot pieces for connector wires. Strip 6" of the outer insulation off the longer pieces and all the outer insulation off the foot long piece. Strip 1/2" off all the ends to expose bare wire.
Other parts - Some connector strips/blocks or wire nuts,18-gauge wire, a power switch, a 15-amp buss fuse and holder, some miscellaneous parts and screws.
To hook all this up:
Enclosure:
Select or make a suitable cabinet for the controller. While you could mount it all on a flat board, open circuitry with 120VAC is a bad idea. A piece of 1/4" plywood with a plastic bread storage container on the back side to cover the wires will work if you don't want anything fancier.
The PID -
Mount the PID on the board/cabinet. Yours may have come with a case or mounting plate of some sort, so mount it as needed.
Connect the thermocouple to the + and - contact screws. Be sure to observe the polarity of the probe! You may need to use a socket that matches the cord type.
Connect two of the 12" long 14-gauge wires to the AC POWER screws. One should be blacks and the other white (from the extension cord). If the PID has a ground terminal, connect a green wire there.
Connect two 12" long 18-gauge wires to the DC SSR Control screws. They are + and - so it is best to use red and black wires.
There may be some additional jumper wires or clips to connect on the PID as the directions will tell you.
On the SSR:
Mount the SSR on the heat sink as described in its instructions (it may recommend using heat sink compound, which is a good idea). Make sure the cabinet or enclosure has sufficient room to aid cooling.
Connect the red/black wires from the PID to the corresponding+/- DC CONTROL contacts on the SSR.
Connect the black AC wire on the female piece of extension cord to one of the LOAD contacts on the SSR. Connect a 12" long 14-gauge black AC wire to the other LOAD contact.
Mount the SSR, heat sink, and the fan so the air blows through the fins and cools the SSR.
The fan connects to the 120VAC buss strips. (see POWER below)
POWER:
Take the 10-foot extension cord and cut it into four pieces as described in the parts list. There will be a common wire (white) and a load wire(black) and a ground wire (green). This will become the power-in and power-out cords and connection wires.
There will be several things connected to these cords, so installing two power buss/multi-connection strips is simplest and safest, but wire nuts will work. AC connection wires will be white and black. Securely fasten the male and female power cord pieces to the cabinet with cable clamps of some fashion.
Install a SPST power switch and a 15 amp fuse. Connect the black wire from the male power cord (the 6-foot-long piece with a plug) to the switch and the switch to the fuse.
Install a black AC wire from the fuse to the load power buss. At this buss the connections are made to:
The 12" black wires from: The load contact on the SSR: The PID: and The fan.
The white wire from the power cord goes to a common buss at which the connections are made to:
The white wire on the Female power cord end (3-foot piece with a socket): The PID: The fan.
The green wires are connected together.
The toaster oven (or controlled device) plugs into the female cord. The male cord will plug into the wall socket.
Insert the thermocouple into the oven chamber. Affix as needed. If the thermocouple is installed just below the rack/grate/shelf, it can be affixed with a twist of bare wire. That way it reads the temperature close to the blade being tempered. Simplest way of installing is drilling a hole in the back or side and sticking the TC through.
You only want the metal probe in the oven, not its wires. Use a longer probe if needed for larger ovens. The tip of the probe is what reads the temperature, so as long as the tip is where the knife will sit on the rack, it will be fine.
The operation of the PID is simple and the instructions give the setup and programming. A good supplier will offer support help. The basic operation is to set the desired temperature (set point or set value) and turn the control program on. The toaster oven is permanently set at its highest setting and will be turned on and off by the controller and the power switch. The controller will allow the power to flow to the oven until the temperature is reached. Then it will cycle on and off to maintain that setting. The PID will auto tune itself to learn how to hold the temperature evenly. There are a lot of strange words, like hysteresis, in the instructions, but once set up it is pretty simple to operate.
Let the oven run for 30 minutes before placing the blade in to temper it.
Hope this helps clear some of the mystery.
Stacy
Some components can be found in thrift stores, other from online suppliers, and most everything can be purchased on Amazon or Ebay. Search for PID, Thermocouple K, SSR, Thermocouple plug connector, 120V cooling fan.
The Oven:
Any manual control toaster oven will do fine. You don't want a digital control oven. One of the old twist-dial types for a few dollars from a thrift store will be perfect. It only needs to be able to set the oven on HIGH or ON. You are going to permanently set it on the highest setting. It needs nothing modified beyond a small hole drilled to allow the thermocouple to stick inside. Some folks wrap a blanket of insulation around the oven to get a little more efficiency. That is a good idea but use the proper insulation. You want a jacket insulation blanket, which controls the loose fibers, like a water heater wrap from the hardware or plumbing shop. Wrap the entire toaster, including the back, and tape the jacket with duct tape. Leave a flap to drop over the front door. This will greatly help the oven regulate temperature and hold a somewhat higher temperature.
The PID:
Most cheap PID controllers are pretty much the same. You want 120VAC input and the ability to take a type K thermocouple.
They often come as a package deal with the PID, SSR, heat sink, Thermocouple, and wires.
Amazon search - PID Temperature Controller Set, PID Temperature Controllers Thermostat Regulator, SSR 40DA Solid State Relay AC 100 to 240V, White Heat Sink and K Type Sensor Thermocouple
The Thermocouple:
The Thermocouple that they often give you with those controllers is pretty useless for most of our purposes, so you will likely need a new one. The temperature range needs to match the desired use. If it is going into an electric toaster oven, it just needs to be a type K that is long enough and rated around 1000F. (BTW, there is a + and - wire, make sure you hook them up right or the display will read wrong.) If your TC has a plug-in probe cord. get a corresponding K-type socket to connect to the PID.
You don't want the ceramic coated TCs for a tempering oven. Just a metal clad probe.
Amazon search - 3M K-Type Thermocouple 100mm Sensor Probe Temperature From -100°C to 1250°C
How it works:
The SSR is actuated by the DC output voltage from the SSR control circuit on the PID.
The SSR can control 48-480VAC circuits. The SSR amperage rating needs to be enough to run the device being controlled, plus a bit. Most folks just use a 40-Amp SSR. You will need a heat sink on the SSR to keep it from burning out (they only will take 3-5 amps otherwise). A small fan, like from a computer, should be used to cool the heat sink.
A 10-foot 120VAC 15-Amp rated 14-gauge extension cord. It will be cut into four pieces - 3-feet with female socket; 5-feet with the male plug; two 1-foot pieces for connector wires. Strip 6" of the outer insulation off the longer pieces and all the outer insulation off the foot long piece. Strip 1/2" off all the ends to expose bare wire.
Other parts - Some connector strips/blocks or wire nuts,18-gauge wire, a power switch, a 15-amp buss fuse and holder, some miscellaneous parts and screws.
To hook all this up:
Enclosure:
Select or make a suitable cabinet for the controller. While you could mount it all on a flat board, open circuitry with 120VAC is a bad idea. A piece of 1/4" plywood with a plastic bread storage container on the back side to cover the wires will work if you don't want anything fancier.
The PID -
Mount the PID on the board/cabinet. Yours may have come with a case or mounting plate of some sort, so mount it as needed.
Connect the thermocouple to the + and - contact screws. Be sure to observe the polarity of the probe! You may need to use a socket that matches the cord type.
Connect two of the 12" long 14-gauge wires to the AC POWER screws. One should be blacks and the other white (from the extension cord). If the PID has a ground terminal, connect a green wire there.
Connect two 12" long 18-gauge wires to the DC SSR Control screws. They are + and - so it is best to use red and black wires.
There may be some additional jumper wires or clips to connect on the PID as the directions will tell you.
On the SSR:
Mount the SSR on the heat sink as described in its instructions (it may recommend using heat sink compound, which is a good idea). Make sure the cabinet or enclosure has sufficient room to aid cooling.
Connect the red/black wires from the PID to the corresponding+/- DC CONTROL contacts on the SSR.
Connect the black AC wire on the female piece of extension cord to one of the LOAD contacts on the SSR. Connect a 12" long 14-gauge black AC wire to the other LOAD contact.
Mount the SSR, heat sink, and the fan so the air blows through the fins and cools the SSR.
The fan connects to the 120VAC buss strips. (see POWER below)
POWER:
Take the 10-foot extension cord and cut it into four pieces as described in the parts list. There will be a common wire (white) and a load wire(black) and a ground wire (green). This will become the power-in and power-out cords and connection wires.
There will be several things connected to these cords, so installing two power buss/multi-connection strips is simplest and safest, but wire nuts will work. AC connection wires will be white and black. Securely fasten the male and female power cord pieces to the cabinet with cable clamps of some fashion.
Install a SPST power switch and a 15 amp fuse. Connect the black wire from the male power cord (the 6-foot-long piece with a plug) to the switch and the switch to the fuse.
Install a black AC wire from the fuse to the load power buss. At this buss the connections are made to:
The 12" black wires from: The load contact on the SSR: The PID: and The fan.
The white wire from the power cord goes to a common buss at which the connections are made to:
The white wire on the Female power cord end (3-foot piece with a socket): The PID: The fan.
The green wires are connected together.
The toaster oven (or controlled device) plugs into the female cord. The male cord will plug into the wall socket.
Insert the thermocouple into the oven chamber. Affix as needed. If the thermocouple is installed just below the rack/grate/shelf, it can be affixed with a twist of bare wire. That way it reads the temperature close to the blade being tempered. Simplest way of installing is drilling a hole in the back or side and sticking the TC through.
You only want the metal probe in the oven, not its wires. Use a longer probe if needed for larger ovens. The tip of the probe is what reads the temperature, so as long as the tip is where the knife will sit on the rack, it will be fine.
The operation of the PID is simple and the instructions give the setup and programming. A good supplier will offer support help. The basic operation is to set the desired temperature (set point or set value) and turn the control program on. The toaster oven is permanently set at its highest setting and will be turned on and off by the controller and the power switch. The controller will allow the power to flow to the oven until the temperature is reached. Then it will cycle on and off to maintain that setting. The PID will auto tune itself to learn how to hold the temperature evenly. There are a lot of strange words, like hysteresis, in the instructions, but once set up it is pretty simple to operate.
Let the oven run for 30 minutes before placing the blade in to temper it.
Hope this helps clear some of the mystery.
Stacy
Fan ! Without fan inside ten PID will not give you uniform temperature ................
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Natlek likes to add a circulation fan in his ovens. You can do that, but it will add to the complexity of the build.
My plans are simple and work.
Of the hundreds of commercial and home built HT and tempering ovens I have personally seen and used none had a circulation fan. They all worked just fine. I believe that if it was a good improvement the major companies would long ago have incorporated it.
If you like the idea of a convection oven for tempering, look for a used in-the-wall or countertop convection oven in the local "For Sale" lists. You can find them surprisingly cheap. I have a 30" wide, digital control, in-the-wall, KitchenAid Convection oven that I will install after some remodeling. I bought for $50 still in the box. It was never installed by the first owner. Besides an occasional casserole, it will do a lot of tempering.
Again, Natlek has his methods, and they work for him.
My plans are simple and work.
Of the hundreds of commercial and home built HT and tempering ovens I have personally seen and used none had a circulation fan. They all worked just fine. I believe that if it was a good improvement the major companies would long ago have incorporated it.
If you like the idea of a convection oven for tempering, look for a used in-the-wall or countertop convection oven in the local "For Sale" lists. You can find them surprisingly cheap. I have a 30" wide, digital control, in-the-wall, KitchenAid Convection oven that I will install after some remodeling. I bought for $50 still in the box. It was never installed by the first owner. Besides an occasional casserole, it will do a lot of tempering.
Again, Natlek has his methods, and they work for him.
Last edited:
Somewhere in March I will open thread about my new HT and tempering oven ...all in one case . I wait for some parts and tools to make them .Tempering oven would be very cheap to make . . .. ..
And while we're on the subject of tempering steel ................Often here someone shows steel with all the colors of the rainbow after the tempering process. And they get the answer that it's from touching with fingers, oil residues and whatever else.......... That thus colors don't mean anything
On that Kephart, one part of steel is coated with a thin layer of engine oil, part with quenching oil, part wiped with acetone, part with alcohol, part touched with sweaty fingers, I even put Danish oil before tempering ........ .....And here it is after tempering at 230 Celsius ............How is this possible ? Why I get ALWAYS one color and it was
matching color from tempering color chart ? Why I never get that *rainbow* Stacy ?
Note.......the second cycle at 230 degrees Celsius lasted over ten hours! Went home and forgot what I had in the oven. .......
On that Kephart, one part of steel is coated with a thin layer of engine oil, part with quenching oil, part wiped with acetone, part with alcohol, part touched with sweaty fingers, I even put Danish oil before tempering ........ .....And here it is after tempering at 230 Celsius ............How is this possible ? Why I get ALWAYS one color and it was
matching color from tempering color chart ? Why I never get that *rainbow* Stacy ?
Note.......the second cycle at 230 degrees Celsius lasted over ten hours! Went home and forgot what I had in the oven. .......
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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I agree with scanniaman, the home kitchen oven is a good choice. The OP said his spouse forbid it, thus my re-post of the article in the stickys.
Another option is a used kitchen oven in the shop or garage.
Natlek - I'm not going to argue over older threads topics or the different equipment we use. Let's just agree that you have your ways of doing things and asking questions. I prefer to go with what is common use and ask things in a less attacking method. That's the last I will comment here. Feel free to send me an email or PM if you want to discuss it more.
Most of the burnout, powder coat, and HT ovens hobby knifemakers here in the USA don't have fans. Most home ovens don't either (convection ovens are starting to become more common in the kitchen, though). Industrial ovens have them, but they are much bigger and start at $30,000.
This is a standard $4,000 Cerakote/powdercoating oven that many shops have for tempering and such. It has no fan.
Another option is a used kitchen oven in the shop or garage.
Natlek - I'm not going to argue over older threads topics or the different equipment we use. Let's just agree that you have your ways of doing things and asking questions. I prefer to go with what is common use and ask things in a less attacking method. That's the last I will comment here. Feel free to send me an email or PM if you want to discuss it more.
Most of the burnout, powder coat, and HT ovens hobby knifemakers here in the USA don't have fans. Most home ovens don't either (convection ovens are starting to become more common in the kitchen, though). Industrial ovens have them, but they are much bigger and start at $30,000.
This is a standard $4,000 Cerakote/powdercoating oven that many shops have for tempering and such. It has no fan.
Stacy , mu friend I'm sorry if you take that I ask in *attacking method* . I am Macedonian . I was raised to speak what I think and to ask direct question whenever I have some doubt .
Now about that $4000 Cerakote oven you posted .............It is convection oven and have FAN
Next time don t look just in picture , read description 
Last edited:
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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My error. Yes, that one has a fan. I was typing too fast and didn't say what I meant. I changed the post comments. Getting old ... I can't even blame it on translating from Macedonian.
My point was few makers have one like that. It was the cheapest I saw in a quick search for convection tempering and similar ovens. Most were $15,000 and up.
Среќна Нова Година
My point was few makers have one like that. It was the cheapest I saw in a quick search for convection tempering and similar ovens. Most were $15,000 and up.
Среќна Нова Година
Used toaster ovens are so available and cheap at yard sales, consignment shops, Goodwill, etc and even convection type toaster ovens. Then add that $22 PID system that Stacy linked to above and you've got a nice tempering oven at very low cost.
My wife tossed a convection toaster oven (she wanted a new type - I don't argue with wife about what she wants) so I took the "thrown away" toaster oven, added PID control and it works just fine. I did remove cover and wrap with some 1/2" Ceramic Fiber Blanket around the top and side. It now holds±1°F just fine.
My wife tossed a convection toaster oven (she wanted a new type - I don't argue with wife about what she wants) so I took the "thrown away" toaster oven, added PID control and it works just fine. I did remove cover and wrap with some 1/2" Ceramic Fiber Blanket around the top and side. It now holds±1°F just fine.
bladegrinder
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I did the same, took a convection toaster oven apart, lined it with ceramic fiber, wired the fan so it stays on, added a pid and it will keep no more then a 3 degree swing. I also use it for stuffed jalapeño peppers.
Stacy E. Apelt - Bladesmith
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For those wanting plug and play, the Oster Convection Oven 8in1 is less than $200. Digital control, good size capacity 200-450°F.
The plus is it will cook two 16" pizzas as well as temper a batch of knives.
The Black and Decker simple convection countertop unit is barely more than a bottle of Blantons.
The plus is it will cook two 16" pizzas as well as temper a batch of knives.
The Black and Decker simple convection countertop unit is barely more than a bottle of Blantons.
That is what PID and thermocouple read .Temperature swing in steel which you temper will be + - much less than that 3 degree ...... with fan on . I spend days in making test with this thing ...... https://www.bladeforums.com/threads/building-tempering-oven.1607678/page-3