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Burnout oven any good for heat treat?
- Thread starter jwesthurl
- Start date
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
- Messages
- 37,721
I have several from doing jewelry casting. They worked OK for small carbon steel small blades, but I was Sooooo glad when I got a HT oven. What I use them for now is tempering small high carbon blades. This allows the blade to go from quench to temper in just a minute or two, without having to go inside to the kitchen oven, or wait for the HT oven to drop 1000 degrees.
Unless it is a new type, most have a simple timer style pyrometer control. This just determines how long the coils stay on and how long they stay off. This works, but will drift upward with a long heat...and the heat dumps drastically when you open the door. The re-bound time to get back to temperature can be quite a while.
Adding a PID, SSR, and TC to the burnout will solve the temp control problem, but won't make the oven work any better. Burnout kilns aren't designed for fast heating or super tight temperature control. They are designed to slowly heat up and melt the wax, then continue to slowly heat and burn out the carbon residue. The temperatures used are between 700F and 1350F. Close regulation is not needed. Big swings in chamber temperature don't matter. The one word you need to remember about burnout kilns is SLOWLY...they take a long time to come up to fully soaked at 1500F.
Also, most burnout kilns have a small cubic chamber. Some are rectangular, but most aren't. This gives you a lot of height you don't need, and not the depth you do need. Try and not place the blade from corner to corner with the tip right in the corner. This may get very uneven heating ( and overheating of the tip).
The dial may go to 2000F, but my car speedometer also goes to 120MPH....neither will likely hit the top end. Burnout ovens are useless for stainless HT. Above 1500-1600F they are not good at all.
If it is free, or less than $50, it is worth thinking about. But it will take at least another $100 to make it work right...and then it will still be a pretty poor HT oven.
$150 will HT about 60 carbon steel blades at Peter's HT ( in three batches of 20), or 15 blades at $10 each elsewhere. That will give you a lot of time to work up your skills in knifemaking and not worry about HT. Once your knives are well made ( with quality professional HT), selling a few of the better ones will buy you a real knifemaker's HT oven.
Unless it is a new type, most have a simple timer style pyrometer control. This just determines how long the coils stay on and how long they stay off. This works, but will drift upward with a long heat...and the heat dumps drastically when you open the door. The re-bound time to get back to temperature can be quite a while.
Adding a PID, SSR, and TC to the burnout will solve the temp control problem, but won't make the oven work any better. Burnout kilns aren't designed for fast heating or super tight temperature control. They are designed to slowly heat up and melt the wax, then continue to slowly heat and burn out the carbon residue. The temperatures used are between 700F and 1350F. Close regulation is not needed. Big swings in chamber temperature don't matter. The one word you need to remember about burnout kilns is SLOWLY...they take a long time to come up to fully soaked at 1500F.
Also, most burnout kilns have a small cubic chamber. Some are rectangular, but most aren't. This gives you a lot of height you don't need, and not the depth you do need. Try and not place the blade from corner to corner with the tip right in the corner. This may get very uneven heating ( and overheating of the tip).
The dial may go to 2000F, but my car speedometer also goes to 120MPH....neither will likely hit the top end. Burnout ovens are useless for stainless HT. Above 1500-1600F they are not good at all.
If it is free, or less than $50, it is worth thinking about. But it will take at least another $100 to make it work right...and then it will still be a pretty poor HT oven.
$150 will HT about 60 carbon steel blades at Peter's HT ( in three batches of 20), or 15 blades at $10 each elsewhere. That will give you a lot of time to work up your skills in knifemaking and not worry about HT. Once your knives are well made ( with quality professional HT), selling a few of the better ones will buy you a real knifemaker's HT oven.
- Joined
- Sep 17, 2013
- Messages
- 430
Thanks for responding Stacy. He was asking $100 but I got him down to $50. It looks a little rough, but he insists that it is very reliable. The chamber is rectangular, I believe close to 6x8x12 inches deep is what he said.
I may just buy it and try to get my feet wet with heat treating just for the heck of it. I am currently sending my knives out but I would like to learn.
I may just buy it and try to get my feet wet with heat treating just for the heck of it. I am currently sending my knives out but I would like to learn.
- Joined
- Apr 16, 2008
- Messages
- 814
I have two they work good converted to PID hold temp. within a couple degrees.
