Knife Material Matters: How to Build a Heat Treat Oven Control Box

I’m going to skip right over the oven build itself and get into the control box. This is the part where a lot of people are unsure of how it works. It’s actually much easier than you might think!

If you need any help building the oven let’s discuss it on Instagram!

Disclaimer

This is only a guide. Use on your own risk. If you are at all unsure please ask for help!

This guide is based on a supplied power of 220 volts.

⚠️ Do not attempt to run this on 115 volts!!

Wiring Diagram

I’m including an easy to follow wiring diagram to show you how each component is connected.

Here is what you will need 

➡️ I put all the parts you will need in a list on Amazon.

  1. One  “PID” This is what controls the oven temperature. For our oven we want a PID  that can handle temperatures up to 1200°c ( 2200°f )or more. I recommend the Inkbird itc 100VH. If you buy a different PID make sure it is 110-240 volts input  and has a relay output in DC volts (3 – 32 volts DC) .
  2. One heating coil rated for 3000 watts. I recommend buying a finished coil, they are inexpensive and much easier than making your own. 
  3. One solid state relay or SSR for short. This relay allows for constant on and off switching of the heating coil needed for your oven. 
  4. One thermocouple that can measure up to 1200°C ( 2200°F ) I recommend option #2 from my list it will last longer than the standard ceramic Thermocouple. 
  5. One DPDT ( double pole double throw ) power switch. The one I listed is easy to turn off with gloves on but you can use whatever switch you like. 
  6. One fuse holder with a 1 amp fuze. This isn’t a must but it will protect your PID if something goes wrong.
  7. One Porcelain screw terminal. To make the electrical connections from the heating coil to your PID. Plastic connectors will not work!
  8. One project box to put all the electronics in. A metal or aluminum box is ideal for this but a plastic box will work if you dont mount it directly to the oven.
  9. Two wire connectors of your choice. Plastic is ok here. 
  10. Miscellaneous wires. Silicone insulated wire would be best for this application because it doesn’t dry out and get brittle over time. I recommend using 2mm wire on all line voltage ( 220 volt ) connections inside the control box!

With this, you get your control box working!

Control box with alarm light

Want a fancy alarm light, too? Or a buzzer?

11. OPTIONAL Signal lights or buzzers. These can be wired to show when the heating coil has power or to alert you of a high or low temperature alarm. To use them as an alarm signal you will have to set a maximum and minimum operating temperature on your PID.  

The following wiring diagram shows the setup with the optional lights/ buzzers.

I would be happy to answer any questions you might have and hope to see some home made ovens from all of you real soon! Reach me on Instagram at @knifematerial.at!

Cheers,

Keith


Read Keith’s previous post: An Abrasive Discussion.

This post is part of the Knife Material Matters column by Keith from knifematerial.at.

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