Heat-treat oven/furnace purchase: what to look out for?

[ThinWoodsman]

This weekend, I'm going to drive around and look at a few (used) options for a heat-treat oven. There are basically two types I'm looking at: kiln (e.g. evenheat, paragon), and muffle furnace, all small ovens running at 110V. I've already looked up the specs and such, so I've determined the suitability for heat-treating ahead of time.

What sort of problems should I look for when evaluating these devices? I know that the thermocouple and the elements are the most likely to cause problems; how can I verify that they are in working order? Is there a quick (5-15 min) test to demonstrate the reliability of the oven? Any gotchas I should worry about?

Thanks

 

[pdentrem]

Have to run it and test the draw and temperatures. I have seen the elements test okay but the unit would not get up to temp.

 

[Diecutter]

I have two Paragon PKM9D electric furnaces and have been heat treating steel dies in O-2, L-6 and 0-1 for decades. They are quite reliable. As far as what to look for in a furnace. Make sure the INTERIOR SIZE is large enough for your use. Make sure the max. MAX TEMP. is high enough for your use. Plug it in and make sure the temp rises quickly and that the buttons on the keypad work. Keep a spare element on hand. Elements are not expensive but once up to heat the first time they become brittle and can't be moved around. I have had them last for many years, but lost one when trying to case harden (they don't like fumes corroding them).

 

[ThinWoodsman]

Plug it in and make sure the temp rises quickly and that the buttons on the keypad work. Keep a spare element on hand.

Good to know. I'll check the expected ramp-up times for the different models. I don't want to spend the time heating the furnace up to 2000 F and then cooling it back down so I can move it, but checking how fast the temp rises is a good idea. Maybe set it to cut off at 400 or so, good check of the thermocouple as well.

I suppose that would leave the possibility of elements that don't get up to max temp, as pdentrem mentioned. But for the price-point, replacing elements is not a big deal.