Kanthal furnace

[LaurenceOs]

Hi Chaps,

I want to make my own furnace, theres a video on youtube for a kanthal furnace and a link: http://kanthal.velp.info Which shows you how to make one, but i have a few Q's

What is the Crucible to be made of? it doesn't seem to mention on the site.
What else can be used as a power source? He uses and old welder.
Where can i find crucible pliers, or even PPE?
Is this the best way or is there a better way?

Anything else you want to mention, all opinions welcome..

 

[EVO-AU]

LawrenceOs: There is a site WWW.LindsayBks.com that publishes all kinds of how-to stuff. Mostly about metalworking. But you have got to see the website. I guarantee you will be impressed. Anyway, there are two furnaces in which you might be interested. Big Bertha ( electric ) and a real gem called "A Crucible Furnace". Both of these were designed by a gentlemen that has a tremendous background in metal working. Unfortunately, passed on a bit ago, however his books and pamphlets are available on the Lindsay site.

I am currently building the crucible furnace. My last furnace ( built in the eighties ) was hairdryer motivated and worked fine. But things do fall apart after a few years. Anyway, pull it up. It's good. Good luck, Phill

 

[leavemealone]

Good morning laurence,
my first "furnace" was simply a propane torch.Very bad idea.I always preach "right tool for the right job" so now I have a ceramic kiln that I purchased for $25 and works great.I wait until I have enough material to justify firing it up.It is great to see the material in its different melt stages.If I need something melted but not enough to crank up the furnace I just use my MAPP or Oxy/Acet. torches.I love the oxy/acet over mapp because I can really dial in a flame,and you can get a small,portable unit,inexpensively and the fuel lasts for quite some time.
Side note:I have mine setup for propane and O2,works like a dream,just DO NOT use it on steves melting dish furnace.....thats one mistake I wont make again.
One more side note:You can make your own kiln VERY easily.You can purchase the elements,and used power supplies on ebay relatively inexpensively,you can purchase refactory or "fire bricks" at any concrete manufacturing facility(Rinker,Tarmac etc).Make sure you use an element that is rated around 2000 degrees Ferenheit.When setting up your element,use some small steel "hooks" that are used to hang pictures on a wall,place the threaded ends between the bricks as you add the bricks then hang the element within those hooks.Make sure you place the hooks in strategic places so the wire does not sag in between,potentially touching itself and shorting.Thats pretty much it.The bricks are around $1.25 U.S. the element should be around $20-25 and you should be able to find a supply for less than $30.All in all you should have less than $100 into a kiln you've built yourself in a shape that best fits your needs.
Johnny

 

[LaurenceOs]

Where to buy the actual kanthal wire though? the only bits i can find are on ebay, they're expensive plus shipping.

 

[leavemealone]

No problem laurence.It doesn't have to be kanthal, http://shop.ebay.com/?_from=R40&_trksid=m38&_nkw=kiln+element .This kanthal element is 110 volt http://cgi.ebay.com/KANTHAL-A1-HEATING-ELEMENT-4-KILN-as-nichrome-wire_W0QQitemZ310144315033QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item48360aae99&_trksid=p3286.m20.l1116 and can be made into a small furnace for small crucibles/cupels.Here's an element thats 40 feet long http://cgi.ebay.com/40-ft-18-Ga-Kanthal-Heating-Element-Wire-Free-Shipping_W0QQitemZ130311070818QQcmdZViewItemQQptZBI_Connectors_Switches_Wire?hash=item1e57252462&_trksid=p3286.c0.m14&_trkparms=65%3A1%7C66%3A2%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50 right now its at $22.If he wants too much to ship it to you,let me know and I'll get it and send it over.
Johnny

 

[LaurenceOs]

hang on how did u manage the kiln for $25??

 

[leavemealone]

LOL......craigslist and a lot of patience.Craigslist is a website over here that people can post things for sale for free.Simply look up your area and what you are looking for and you get a list.
Johnny

 

[LaurenceOs]

Im no good with patience lol I'll build one, what other means of power supply do you suggest Johnny?

 

[leavemealone]

Pretty much any that has the appropriate wattage and amperage for the element you are using should do fine.You can also do some research online and get resistance levels for any distance and gauge wire you intend on using.
Johnny

 

[goldsilverpro]

Except for doing assays, I really hate electric furnaces. Neither the lining or the elements take kindly to the corrosive fumes and spilled slag that are commonly generated when doing routine refining work.

 

[leavemealone]

Yeh they also don't like soda ash,but thats why I built a gas furnace with the firebricks.
Johnny

 

[LaurenceOs]

Johnny, what do you think about this? http://cgi.ebay.co.uk/12-METRES-ELE...ms=65:1|66:2|39:1|240:1318|301:1|293:1|294:50

I messaged that guy with the 40 ft kanthal stuff about shipping but i've had no reply.

 

[leavemealone]

Looks great to me.It will get plenty hot enough to melt almost any PM,Its long enough to make a pretty decent sized furnace,and the price sounds really good too.I give it a thumbsup.
Johnny

 

[LaurenceOs]

not a little thin at .4mm? i'd expect it to bust all the time

Also measuring temperature? Any suggestions?

 

[leavemealone]

Well it said is was capable of 1300C ,you need less than 1100C to melt gold.So you should be ok.My kiln only goes up to 2000F thats less than 1100C.You may want to consider just getting a mapp torch for now until you have processed some of the gold.I used one for over a year when I started.Theres nothing wrong with it,god knows plenty of people on here use them.It would be a very fast,not too expensive solution to your problem.
Johnny

 

[LaurenceOs]

Thanks johnny, i swear googles not as useful as people make out

 

[leavemealone]

You are more than welcome.

 

[lazersteve]

I really hate electric furnaces. Neither the lining or the elements take kindly to the corrosive fumes and spilled slag that are commonly generated when doing routine refining work.

I can second this one. It seems every other time I use my electric box kiln I have to repair something on it. Spills will eat up the firebrick lining very quickly.I repair mine with castable refractory that contains an aggregate of fine gravel.

On the same subject be really careful using certain aggressive fluxes in your fire clay crucibles as the flux can eat through them very rapidly, especially if iron is present in the material.

On the upside they make for easy casting of gold into graphite. Since the dish gets evenly heated completely through, the gold stays molten for a longer time and pours like a dream. I preheat the graphite by setting it on the top vent hole in the furnace while the gold comes up to melting temperature.

The mini-furnace with straight MAPP gas is my favorite way to melt a small amount of gold (less than 1.5 ounces) quickly.

Steve

 

[LaurenceOs]

But doesn't the gas on those map torches run out pretty quick?

 

[leavemealone]

No I've used them for years.You will only be using it a couple of minutes at a time.1 bottle will probably last several weeks unless you use it a lot,which means you are getting more gold and thats a great thing.It is very cost effective to purchase one.You only buy the torch once,you only have to replace the tank which is less than $10.
Johnny