Old Heat Treat Oven Help

[DCL Knives]

Hello, I recently picked up this old K.H. Huppert ht oven from a local shop.

I rewired the plug and turned it on for a quick test. It was able to get up to around 1500 °F in about 20 min. The dial to adjust the temperature was broken, so I wasn't able to test it much more than that.

The strange thing I noticed were three holes in the back of the oven. They go completely through all the insulation.

I looked around online and saw that some other similar models had the same thing. Is there a good reason that they are there? Should I plug them with something, or is that how it is supposed to be? The back of the oven is perforated and did not get abnormally hot.

I tried reaching out to the company, and did not hear anything back from them. If anyone has any advice I would greatly appreciate it.

Also, eventually I plan on upgrading it to PID controlled. The old analog controller looks extremely complicated (quickly pulled it apart to see if the dial repair would be easy). If anyone has any info on how the old analog oven controls function I'm all ears!

Thanks,
Drew

 

[Stacy E. Apelt - Bladesmith]

It is an old burnout oven. The vents are to let out the smoke and vapors from the melting and burning wax. Not great as HT ovens, but will work for carbon blades. Those timer type controllers (on and off for various time percentages) aren't accurate, regulated, or programmable. You will either have to sit and baby it the whole time or change it to a PID control (pretty easy to do).

If using it for HT, fill the vent holes with kaowool, satanite, or firebrick plugs.

 

[DCL Knives]

Thanks Stacy! I'll give it a shot, and likely will end up converting it to PID control.