Picture of DIY Mini Forge
Forge Diagram.jpg
Lately I've been wanting to make some pocket knives for my friends and family.. So, I'm going to make a simple mini forge at TechShop to temper the steel...

This forge is meant to burn coal.. You can you lump charcoal and wood, but it will take a lot more of it to keep the heat at the right temperature for the duration of the process..

Step 1: Things You Will Need..


-- 1 1/4" Scrap Black Iron Pipe..
-- 1/2" Scrap Black Iron Pipe..
-- 1 1/4" Scrap Iron Pipe Tee..
-- 1 1/4 Scrap Iron Pipe Cap..

-- 1/8" Scrap Angle Iron..

-- Small Scrap Plate of 1/8" Steel..

-- 11" Diameter Scrap Brake Drum..

-- Cheap Hairdryer or Other Blowing Device..


-- Horizontal Bandsaw..

-- Cold Saw..

-- Flow Waterjet..

-- Angle Grinder..

-- Lincoln 255xt (MIG)..


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bennelson2 years ago
I built a similar forge recently completely from recycled and salvaged materials. A welder and angle-grinder were the only tools needed.

It was pretty neat to go from never having done any blacksmithing before, to building a forge, and starting to work on some metal projects in just one afternoon.

I had the Bob Rubert  blacksmithing video and made some little twisted coat hooks from old-fashioned square nails. I also tried a railroad-spike knife, which turned out ok. Not as great as I would have loved, but it was the first time I ever tried anything like it!

Thank you for the link - very nice!

MR.. (author)  bennelson2 years ago
Thats awesome!!
It really is amazing how easily you can build a forge and get going in one day.
I can't wait to show y'all the stuff i'll be working on..
You can add a foot operated switch that the Hair dryer plugs into.
lykle2 years ago
Nice writeup, . Pity I can't get coal around here.
I think for now I will stick to my smelting furnace when I need high heat.
But the moment I find some coal, I will come back to this one.
Saved in my "Future Projects" folder.
Just thought i would mention making charcoal out of dense timber makes it last longer and burn hotter. If you can find the very base of a stump from a dense old tree and turn that into charcoal it makes a big difference.
MR.. (author)  Slashie von Chainsaw2 years ago
Yes! Or you could use any kind of hardwood lump charcoal. Either way it won't burn as hot as coal and you'll end up using more of it. But in the end the same result can be achieved with charcoal as it can with coal.
MR.. (author)  lykle2 years ago
Check out http://www.penncoal.com/
lykle MR..2 years ago
Yes, good site, but they do not ship to Cyprus.
And I think it would be way to expensive to ship to here as well.
Never mind, I will use charcoal.
MR.. (author)  lykle2 years ago
Ah, sorry! I didn't realize where your location was.
Pfarmkid2 years ago
I have a old brake drum forge leftover from the previous lan owners (twenty years ago) it used to run for us but then was neglected for years do you have any ideas for a blower??? besides a blow drier???
MR.. (author)  Pfarmkid2 years ago
Sure! Right now I'm actually running a Vacmaster 2.5-Gallon Wet/Dry instead of the hair dryer. I bought it used at a garage sale for 10 bucks! I also will be installing a valve so I can control the air flow. I'll either post the mods I do on this Instructable or make a new one just for the valve install. Let me know how that works out and If you need any other help. Have a great day.
cody.lomas2 years ago
really like the forge design ive been smithing for a couple of years my forge isnt nearly as well constructed all i used was half a propane tank exaust pipe and concrette the motor is just a air matress pump and i got a rail road track for an anvil
MR.. (author)  cody.lomas2 years ago
Thanks! I'm glad you enjoyed!!
cody.lomas2 years ago
also are you hammering your knives or just using the forge for heat treating
MR.. (author)  cody.lomas2 years ago
I'll just be using it for heat treating at the moment.
forge ahead!
oppie2 years ago
Just for reference, look up induction furnace or induction forge. That's how modern heating of iron is done. Very clean and energy efficient. No flame though.
FFTravisM2 years ago
What kinda of temps are you getting? Anywhere near forge welding?
Great instructions.
MR.. (author)  FFTravisM2 years ago
The heat gun I used during the first run topped out. So, I'm not exactly sure how hot it got. The metal was demagnetized at one point and glowed at a similar color as other metals I've worked with. I was able to hammer it down nicely. And I believe if the right fuel is used, this forge will be great for small projects.
oppie MR..2 years ago
Forge welding is quite tricky. You have to get the iron to semi-liquid state (about 2700 F) and have very little or no oxygen. If you do have oxygen at this temperature, you will see something that resembles sparklers - your workpiece is ruined at this point.
Low oxygen is achieved by building the fire very deep. This is best done with coke which you should make ahead of time. Idea is that by the time the air gets to the top of the fire, all the oxygen has been used for combustion of the coal and not the iron.
Here's a very useful chart http://www.abana.org/resources/education/tempil_guide.shtml
MR.. (author)  oppie2 years ago
Again, Thank you so much! Your knowledge is much appreciated kind sir!!!
That looks awesome mate :)
MR.. (author)  RossThePiper2 years ago
Thanks! I'm glad you enjoyed it.
wakabi2 years ago
wow , creativity is devine thanks for the sharing heart.
MR.. (author)  wakabi2 years ago
It was my pleasure!!
oppie2 years ago
Always nice to see interest in traditional blacksmithing with a forge. First time I used a anthracite (hard) coal forge, was amazed at the amount of heat it produced.
For anybody interested there is a wealth of information on www.anvilfire.com
MR.. (author)  oppie2 years ago
Wow!! That site is awesome, thank you for sharing it!
oppie MR..2 years ago
Several places sell a 50 pound cast iron anvil. One place is Harbor Freight. Bad thing is that cast iron is brittle and can shatter. If you can find it, a one or two foot section of railroad rail makes a great anvil. Railroad spikes and track plates are also good for making tools (as are used car springs). Local commuter railroad did a major track upgrade a few years back and there was a good deal of scrap to be found.
With a coal forge - especially with Anthracite, the idea is to turn the "green" coal to coke. Coke is almost pure carbon and burns much cleaner and hotter than green coal. You keep the green coal to the outside of the firepot where it will not only give off its volitiles but it will protect the walls of the firepot from the hotter burning coke in the center of the fire. Feed the green coal from the outsides of the pot and use a tool to push the coke down and towards the center of the pot into the airflow.
If you haven't done so yet, also check out www.abana.org
MR.. (author)  oppie2 years ago
I found a place nearby with railroad track.. I'll be picking some up soon!!
oppie MR..2 years ago
Nice thing about railroad track is that it has so many angles to it. You can use it straight up and use the crown or edged for round-overs. On its side, the hollow is good for forming wide bends. The side of the bottom edge can be ground to an edge for cut-offs (put your hot piece against the edge and hammer on it to make an indent, grab with a tong and break off).
Hammers: depending on your work size, a 1-3 pound ball pein and cross pein hammer is good for the small stuff you had mentioned earlier.
One wonderful thing about blacksmithing is you can make not only ornimental stuff but your own tools as well.
If you are a real traditionalist, you can do forge welding- something I've never mastered (and thus I have an oxy acetylene torch and a MIG welder in the shop).
MR.. (author)  oppie2 years ago
Abana.org is a great site!!
3gghead2 years ago
Is there an advantage to the circular forge that a brake drum yields for the work you're doing? I'm led to believe that a square or rectangular multi-head bed to be more versatile and adaptable to smithing in general. In future designs will you try to accommodate longer and/or irregular-shaped pieces or is this a specific-purpose forge (for knives or whatever)? Are you using the brake-drum just because it's available and easy to work with or because it creates a hot-spot suited to your craft? This is the first "instructable" that's captured my attention and I'm just hoping to fill-in some gray areas. Even if my questions go unanswered, you still have my thanks for being the "everyday hero" that chose to share.
Square things lose heat faster than round things, due to the ratio of area to circumference. But ultimately, ensure the longest dimension is sufficient for the longest object you want to heat all at once.
MR.. (author)  3gghead2 years ago
The reason I used the small brake drum was because it was easy to find. And it suited my needs at the time, which is just tempering small knives at the moment.
MR.. (author)  MR..2 years ago
I'm glad you enjoyed it!!
jell442 years ago
If you could take a parabolic piece of glass from a large screen TV like the older styled 50+" sizes, on sunny days or even partly cloudy days you can get temperatures in the 3000 degree range at the apex of the beam. And have some semblance of temperature control by moving away from the apex.
MR.. (author)  jell442 years ago
I know, there's some sick videos of solar welding and people melting steel by focusing the suns rays... http://www.boreme.com/posting.php?id=19737
jerbear19782 years ago
I would love to see a video of this thing in action.
MR.. (author)  jerbear19782 years ago
I'll definitely will post one when I upload the Instructable of me tempering my blades.
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