# Muffle Furnace -vs- Open Coil Types For Ht. Any Comments?



## countryguy (Jun 19, 2015)

Issue: The refurb muffle furnace we now built runs great. Put in a SOLO PID controller.  But- the Son wants to sell it and get a newer Evenheat. The KF27.  They look sweet and all but I'm just not in the know about open-coils in the chamber and HeatTreat work. he'll do his knives and axes. I'll do usual small parts for various projects. Just HT work anticipated.  Max is 2200 on both.  

Any comments welcome and thanks! 
CG.


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## T Bredehoft (Jun 19, 2015)

If the muffle furnace excludes normal atmosphere (oxygen) I would stay with that. If it is a feature of the Evenheat, go for it. If O2 can be eliminated that will enhance the surface of the heat treated product.


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## JimDawson (Jun 19, 2015)

First, if what you already have does the job, then buying a new one really doesn't make much sense.

For a number of years I used a Blue-M with exposed coils,  Never had any problems.  I have been thinking about buying a pottery kiln to use for heat treating, generally less expensive and much more available on the used market.  Also do to the design, it would be easy to convert to a controlled atmosphere furnace because the bottom is closed and they are top load.  It would be easy to plumb in an argon line from my TIG tank.


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## countryguy (Jun 19, 2015)

Ohh and a follow up-  The Thermocouple is in the middle of the space.   It's noted as 'shapable'  - Should I bend it and mode it over near the wall of the chamber?    Some theory online about using TC's for temp control -vs- direct wall mounted probes.  Reason being that in a setting of  Wall temp -vs- air temp -vs- actual part temp, the wall temp will be closer and should be used.    That's what it noted anyway.    any comments welcome.  I was not sure really where to put these HT type posts.     

Thanks, 
Jeff


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## countryguy (Jun 19, 2015)

Jim,  Yeah - The kid thinks new and shiny is better.  I'm w/ the "rust is a must" folk.       Hope all is well.  Wish I had more time here!  Summer is Firewood (15+ cord)  Hay, house, and honey do's.   Hope everyone is making chips as I'm certainly not of late.   

Tom,  I can port a gas into the Muffle furnace w/ a hookup I can build.   That is what many do to control the O2.   Correct. I'll call and ask about the Evenheat stuff.   

The  was to refurb & sell the muffle. They go for $2K usually w/o a refurb PID on them.   And the Evenheat KF27 is about 1K so the Son sold me on putting a few dollars in my pocket.   But now that the muffle is part of the "shop"  it's certainly under some 'child protective" treaty that it MUST stay.     Am I right? 


Enjoy and HAPPY FATHERS Day to everyone deserving of the phrase.


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## T Bredehoft (Jun 19, 2015)

I'm envious of any 'method' of heat treat, I'm limited to my A/O2 torch and a can of non-detergent engine oil. I temper in the kitchen oven. When I was employed, I'd soak stuff in the Seal-peel tank overnight.


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## Flammable_Solid (Jun 19, 2015)

Thermocouple placement is important.  If you can, make up an embedded TC to better monitor your parts.

Google "furnace survey" to learn about measuring the working zone of your furnace.


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## countryguy (Jun 19, 2015)

Perfectr!  Exactly what I was looking to find out.  Love to dig into this stuff.    You guys Rock here!   

Tommy B.   There are guy's who did "ditch clay" to make a circle forge heated by the torch.    A Thermocouple built into the wall and a temp display could get you going.... I saw a few of those DIY projects.  Let me know if you want some sources.     
Best, 
CG


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