Heat treat oven ?

Keith Willis · Sep 12, 2009

I am wanting to build a heat treat oven,however,other than the box,(and I am not sure of a size)I do not know where to start.Is there somewhere that will show me the materials needed,from wiring,element,thermocouple,controllers along with anything else,and instructions on installing?I don't have 220 in my shop,but will run wire,if that would be a better option.I am not looking for anything large.

Thanks for any help,God bless,Keith

silver_pilate · Sep 12, 2009

I built my oven loosely based on the build located HERE. It was pretty straight forward once I had my head wrapped around it. I also used the supplier listed in the article for the kanthal wire and got my controller and pid from Auber Instruments.

Let me know if you need any help. BTW, here is my oven:

--nathan

P.Brewster · Sep 12, 2009

Here are some links:

Tutorials:
http://www.bladeforums.com/forums/showthread.php?t=456545
http://www.bladeforums.com/forums/showthread.php?t=506521
http://www.bladeforums.com/forums/showthread.php?t=573671
http://www.bladeforums.com/forums/showthread.php?t=538320
http://www.bladeforums.com/forums/showthread.php?p=6281417

Controls:
http://www.auberins.com/

Wire etc:
http://resistancewire.com/mainpage.php/
http://www.ec-securehost.com/PelicanWireCo.Inc./Miscellaneous_Requests.html
http://www.joppaglass.com/elements/mainelpg.html
http://www.budgetcastingsupply.com/Heating_Elements_Controllers.php
http://www.duralite.com/store/scripts/prodView.asp?idproduct=108

I used the last vendor, Duralite - great service and prices.

Figure 20A to be a minimum; Rashid recommends a 30A oven for fast heat and element longevity.

My oven is shown in this thread:
http://www.bladeforums.com/forums/showthread.php?t=659447

It "bolts" together with no mortar.

cooper_luke_10 · Sep 13, 2009

Something I've been unsure about is the length of heating wire I would need for the 240V 10A power supply in Australia.
Using V = IR I think I would use enough Wire to get 24ohms of resistance.
Would this be correct?
Or would I be better off getting a 16A socket put in and use 15 ohms worth of wire?
When I get to build it I think I will aim for something like a 20 * 6 *6 chamber.
I would prefer to use a 10A power supply.
I just thought the guys here who have built their own ovens might know.
Thanks

12345678910 · Sep 13, 2009

cooper_luke_10 said:
Something I've been unsure about is the length of heating wire I would need for the 240V 10A power supply in Australia.
Using V = IR I think I would use enough Wire to get 24ohms of resistance.
Would this be correct?
Or would I be better off getting a 16A socket put in and use 15 ohms worth of wire?
When I get to build it I think I will aim for something like a 20 * 6 *6 chamber.
I would prefer to use a 10A power supply.
I just thought the guys here who have built their own ovens might know.
Thanks

Keep in mind that you are only permitted to place a load on a circuit that is 80% of the supply

10 A supply 80% is 8 amp
16 A supply 80% is 12.8 amp = about 3100watts consistent with other ovens the same size that I have seen.

DrThunder88 · Sep 13, 2009

My home-built kiln uses 20ohm element (40 feet of 18 gauge) at 240VAC to heat the 4.5x3x15" chamber. I remember coming across a recommended wattage per unit kiln volume when I was building mine, but I'll be darned it I can find it. Currently it's 14 Watts/in^3, which is over three times that of a Paragon or Evenheat of similar size. Probably too much but it gets hot fast!

john0270 · Sep 13, 2009

I am also planning on building an electric heat treat oven, but would like it to be about 30" long, anyone here build one this big?

Keith Willis · Sep 13, 2009

Thanks for the replies,not sure if I comprehend it all as of yet,i'm a little slow.Looks like a lot of good information that Patrick provided,thanks Pat.In the time it will take to get my box built.I hope to learn a lot more.Thanks for the help,thanks in advance for anymore help.

God bless,Keith

P.Brewster · Sep 13, 2009

I had a hard time knowing where to start with the wiring. I was comfortable with the math and electrical concepts.

Basically, I realized that I wanted to use the most watts/amps possible from 12g wire on a 20A breaker (thats a common/reasonable size). I simply did not want to run 10g or heavier back to the breaker box.

80% of 20 A is 16 A (80% is the recommended working load). With that number (amps), and your volts, you get resistance (ohms).

Find a chart that compares kanthal wire gauge to ohms per foot. Pick a gauge based on factors described in the tutorial links (longevity vs low power consumption, gauge vs length, etc). Now you have your wire size (gauge) and total length (feet).

I arbitrarily decided that I wanted to use 50ft or less, so mine turned out to be 45ft of 15g, IIRC.

Coil your wire as described in the prior threads.

Or buy a pre-made element.

Build your oven and install the element. Then wire your 220V, 20A power supply to your control and element per tutorials. Both legs must be switched off for safety; only one leg need be switched for temperature control. Ground every exterior metal component.

oldwolf · Sep 14, 2009

john0270 said:
I am also planning on building an electric heat treat oven, but would like it to be about 30" long, anyone here build one this big?

I'm building one about that big using soft firebrick. Just add more brick to the size you want. There is a good tutorial by Dee on Fogg's forum.ttp://forums.dfoggknives.com/index.php?showtopic=13506