Which element to use, and how many watts, for tempering oven build?

nickandersonart

nickandersonart

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Aug 5, 2014
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Hey guys, just curious as to what people would recommend for element choice in building a tempering oven. Seems like the go-to choice are kanthal coils for any kind of high temp oven, but seems like a bit overkill, and unecessary hassle, for tempering oven (correct me if I'm wrong there).

Also, I have a ton of fiber blanket so if I could build just using a metal box or tube and some fiber blanket, and not need to use bricks and carve out channels for coils, the whole thing would be easier.

Is there a better solution like infrared heater or some kind of tube heater that would be better situated? I'm thinking of an interior length of, say, approximately 24-26 inches.

Finally, how many watts would be advisable for the element or elements?

Thanks as always ;)


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what size blades are you going to do and what kind of steel. if doing high carbon steel and stainless like 440C and AEB-L and they are less than 15", get a basic toaster oven from wallyworld for $50. with a toaster oven, get a good thermometer and verify temperatures. my oven has enough racks that the knives go in the middle and are shielded top and bottom from the elements. when tempering, i run it in convection mode, so the air inside is circulating and temps stay even. a regular oven would work ok once you verified temps.
scott
 
I would check Craig's list, habitat for Humanity stores, The Builders' store, Goodwill, etc. for an in-wall oven. If it is a convection oven, all the better. Add PID control for about $50 and it will temper anything but a big sword. New ones are expensive, but salvaged ones or scratch and dent units are cheap. You could also check out some appliance repair and installation contractor, as they might have a used one in the back room.

Another great device is a countertop oven ( bigger than a toaster oven) . These were popular for apartments that didn't have ovens, and are big enough to roast a small turkey. They regularly show up in the box in thrift shops and yard sales. I see them for $20-40.

As an alternate, any regular electric kitchen oven will work just fine. Again, you can make it PID controlled fairly easily, or just add a good bare wire TC and readout to monitor the temp..



If you build it from scratch, you can use your fiber blanket, but you will still need some sort of chamber. The heat can be made by ceramic heat rods, pre-made coil units in ceramic bases ( usually round), or some other heat rod type device. You might be able to salvage a quartz or ceramic heater and make it work. I would think a chamber made from something like 1/2" ins-board ( or maybe cement board ?) would be best. Wrap it in plenty of insulation wool and build a metal shell.
 
Nick's source of cheap ovens is MUCH less in Thailand than we've got around here I'm sure. Should be able to find something just for tempering. HT'ing is a different matter.

Ken H>
 
I made one from duct metal found at local Home Depot.
http://www.bladeforums.com/forums/s...Oven-Completed?highlight=StuNY+tempering+oven
Nice and long for big blades and of course heats up quickly, tracks temperature correctly.
I ended up using this heating element I got from Amazon:
https://www.amazon.com/gp/product/B00ARB37SY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
It is 600 watts, which is probably more than I actually needed but it was nice and long so figured it would heat the oven uniformly.
I basically had a narrow duct inside, wrapped it with fiberglass insulation, then covered it with a larger duct and end caps.
Works great
 
Thanks everyone for the replies! Yes Ken was right, while some things in Thailand are cheaper, there are a lot of things that are far more expensive, or in shorter supply than we have back home in the US. One anomaly out here is that the second-hand scene on goods is almost non-existent compared to the US (oh man do I miss flea markets and garage sales!). Essentially, smaller Countertop ovens exist here but for the price (about 150-200 US) I can build a much better and more insulated one that can do longer blades.

One thing Thailand is great for though is that there are a lot of industrial goods suppliers, so there are many companies selling oven building supplies for industrial applications (hence why when I bought ceramic fiber blanket I had to buy a 22 foot roll of it).

Stacy I'll check out those ceramic heating rods, sounds like a good start. I have the PID controller ready, just need to plug into the oven.

Scott I'll be doing as long as 25" blades, so long is gonna be good.

Perhaps will do the duct metal route plus long ceramic heaters. 600-1000 watts I'd say?


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One thing you can do is make a very simple tempering oven. A 36" long section of 12X12" AC duct and a roll of 1" kao-wool stuffed in it will make a good chamber. Suspend the heat rod from the top and set the blades on the wool on the bottom. Block the ends with fire brick. Lay the TC right next to the blade and connect the heat element and TC to the PID. Primitive, I know, but it will work.

The loose fibers from the wool will be no worry, as they are not heated to high temp or being blown about.
 
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