Author Topic: using a small furnace as a forge??  (Read 3829 times)

Offline bertie_bassett

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using a small furnace as a forge??
« on: April 22, 2015, 01:59:43 PM »
on my ever growing 'to do' list is the need to melt aluminium along with the wish to try some forge work.

im currently thinking of building a small furnace for melting aluminium, something similar/the same as VT's POP furnace looks about right and manageable for me.  and was wondering if it could also double up as a small forge?

seems that if you leave the lid off  and just fill it up with charcoal it would do the job nicely, but im double checking in case im missing something obvious.

so.. am I asking a dumb question? or have a got a stupid idea?
a competent engineer uses the tools and knowledge available, to get a challenging job done.

 An incompetent "engineer" tells his boss that the existing equipment "can't do the job" and to get another machine

Offline awemawson

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Re: using a small furnace as a forge??
« Reply #1 on: April 22, 2015, 02:56:31 PM »
No reason not to, just not the most efficient method of heating.

I used to use my oil fired  furnace for heat treating parts I'd made  -examples being a set of 3MT to 1" bore adaptors to hold die heads. I dangled them into the furnace until cooked, then quenched in a can of oil. That was 25 years ago, and I'm still using then :)
Andrew Mawson
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Offline Will_D

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Re: using a small furnace as a forge??
« Reply #2 on: April 22, 2015, 03:12:21 PM »
Not made it yet (but getting closer) here is my bright idea:

http://madmodder.net/index.php/topic,10544.0.html
Engineer and Chemist to the NHC.ie
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Offline bertie_bassett

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Re: using a small furnace as a forge??
« Reply #3 on: April 22, 2015, 04:16:20 PM »
Not made it yet (but getting closer) here is my bright idea:

http://madmodder.net/index.php/topic,10544.0.html

ah, I knew id seen something similar!  looks a good idea

Im not sure ill be using either very much so don't want to go overboard, an if one tool can do 2 jobs its got more chance of being usefull
a competent engineer uses the tools and knowledge available, to get a challenging job done.

 An incompetent "engineer" tells his boss that the existing equipment "can't do the job" and to get another machine

Offline sparky961

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Re: using a small furnace as a forge??
« Reply #4 on: April 22, 2015, 05:37:28 PM »
It's been a while now, but I made a very nice large drawknife from an old file.  I heated the file in my propane-fired furnace, just laying in there kind of sideways like, and beat it into shape.  You might call it blacksmithing, but that would be too generous.  Then I finished the shaping and smoothing with another file (because the old one was now annealed) and an angle grinder.

Once I got it pretty close I heated it back up again and finished by plunging into oil.  I recently learned that using any old oil is not the best practice for a number of reasons, but sometimes we need to make do.  I didn't bother tempering it.

As a final step I used a flap-disc on an angle grinder to sharpen the edge and honed it to a razor sharp edge with a stone.  I welded some handles on, and I'm still using it today.

So, yes... it does work.  I agree that for hobbyists you should try to have multi-purpose tools when the use is seldom and it can still get the job done.

Offline vtsteam

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Re: using a small furnace as a forge??
« Reply #5 on: April 22, 2015, 09:18:04 PM »
I often used my frst charcoal furnace to forge and heat treat small boring bars for my lathe. Charcoal briquets work fine for this.

I once used real wood charcoal to check the refractory properties of some sand and clay mixes -- rolled into small patties. Since the furnace was only being used for that, I thought I'd just stick a length of 1/2" rebar through the lid opening to forge as well. After about 15 minutes at full blast I thought I saw the rebar move. but wasn't sure. Then i saw it definitely sinking in. Pulled it out and it was white hot at the bottom end and throwing off sparks like a sparkler. It was also shorter by about 2 inches.

When I'd finished with my refractory samples and pulled them out, there was also a nugget of solidified cast steel at the bottom of the furnace.

So, no problem using a small charcoal furnace as a forge. And maybe even melting iron in one, at least inadvertently! This experience is what led me to try my sawed off charcoal cupola several years later-- but without success there.
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Offline vtsteam

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Re: using a small furnace as a forge??
« Reply #6 on: May 18, 2015, 02:05:05 PM »
Bertie just to confirm (though using propane not charcoal at the time) a couple days ago I finished a job to bend two steel bars about 1/2" x 2" x 14" into a drawn out S shape, both needed to be identical, and I easily accomplished that with the plaster of Paris lined furnace.

I'd say a "real" forge (being horizontal and set at a good height)  is handier to use for sure. But for occasional use, in a pinch, you can forge metal with no more than that.
I love it when a Plan B comes together!
Steve
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