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I Forge Iron

$20* forges capapable of welding


reefera4m

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Brand NEWBIE here so sorry if this is old news.

Here's a couple of forges I built for $20* each *(excluding the regulator which I had and scrap materials which I also had). The first design wasn't optimal for even heating so I changed the burner position on the second. #2 has offset burners that create a 'swirl' effect and heat more evenly (though a little slower). Both operate well at between approximately 6 and 12 psi.

Both now have a refractory cement coating over the KOAwool.


If interested I have a complete list of material and tools required - no charge.

Main cost:
12" length of 6" steel pipe = $10
1' KAOwool $8
1 gas valve $2 Harbor Freight

All the rest was scrap but if priced new would be another $10.

Tools used:
MillerMatic 175 MIG Welder
3/4 metal cutting hole saw
4" grinder w/cutoff wheels *$.79 @ HB
3/4" Pipe Threader (not needed if purchasing new nipples)
Drill and tap for the MIG .030 welding tips

The venturi cones were made from 3" lengths of 2" diameter scrap exhaust pipe. The adjusting rod was an old 1/2" carriage bolt welded to a 3/8" black steel 'T'.

Base was made from 2 pieces of 3" scrap angle steel 24" long welded together.

After only 3-4 minutes almost to welding temp and this was before coating the KOAwool with refractory cement.

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  • 2 weeks later...

Couple of modification/enhancements to the original design. I coated the KOAWOOL with refractory cement and then ITC100 - both really help increase the internal temperature by reflecting the heat back into the forge.

Sliding, extendable blade/tool rest. This, along with the fire brick on the 'porch' allows me to position the work piece where I want to and where it will heat the best. The rest can be used to support the work piece on either or both ends with a maximum extension of about 24 inches beyond the 'porch'. Completely removeable for transporting. Made from 1/2" square tubing ( I had to fabricate the guide slots as Home Depot didn't carry 5/16" square tubing).


Rear cover - opposite side hook faces up so that I can just give it a twist to remove, It fits snug on the lugs and snug to the back. Helps retain much more heat than an open back but is removeable for longer blades.


The burner flames using the new offset design.


Tried to get the swirl but doesn't show up in the photo well but heats pretty evenly

After 2 minutes:

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I just saw those last night on welding web- nice work. I had a thought about the ventury mixing cup size. In looking at it I thought it too big, meaning they would run lean. Looking at it running, it seems they are running a little rich but its hard to tell from the pictures. Have you thought about making the air intake adjustable?

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I just saw those last night on welding web- nice work. I had a thought about the ventury mixing cup size. In looking at it I thought it too big, meaning they would run lean. Looking at it running, it seems they are running a little rich but its hard to tell from the pictures. Have you thought about making the air intake adjustable?



Yes, I have. In fact I have two ways to adjust the air. First, moving the nozzles in/out of the venturi cones by adjusting the nuts on the threaded rod and second, and by far the simplest and most effective is by placing a small steel disk partially over the venturi opening. I have two of these disks for each forge and just hold them in place with magnets. I'm considering attaching a swivel point for the disks but the magnets work just fine.
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The hair dryer is used to supply air to the propane to make a fuel/air mixture. Based on the one's I've seen and used and the experience of people I know that have 'blown' propane forges, there are some advantages. By the way, most people use small squirrel cage blower rather than hair dryers.

Advantages:
1. The forge can operate a a lower pressure 3-5 psi as opposed to the 8-10 psi my 'venturi' forge needs. Less pressure usually equates to lower propane use.
2. Blown forges can usually attain higher heat, (more air more heat) making it easier to attain 'welding heat'. If you're going to do a lot of forge welding, a blown forge is probably the way to go.
3. With most blower setups I've seen, there is a way to regulate the air, either a electrical rheostat or some type of shield to restrict the air flow. This allows for easier control of the heat produced (this control can be acheived in a venturi forge by air flow restrictors as well)

Disadvantages:
1. You have to have a source of electricity to power the blower (hair dryer, squirrel cage blower or whatever)
2. Blowers, and especially hair dryers, are usually inexpensive and not terribly robust pieces of equipment. When they stop running you have to replace them before you can use the forge again.
3. Electrical wires/extension cords don't play well with hot steel. I've seen a red hot knife blade slip out of some tongs and land on the extension cord - 4th of July sparks in a heart-beat!

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  • 3 weeks later...

I would disagree, a little, with that advantage. A forge that's designed for forging heat at 8 - 10 psi will not get steel to forging heat at 3 - 5 psi. So while it will operate at 3 - 5, you're not doing much except keeping things warm at that pressure. In most cases, what's done to run at lower pressure is the orifice is enlarged, often just an open pipe, in combination with lower pressure and a blower to get to forging and welding temperatures. The larger orifice means more propane is coming out at a lower pressure so you're not really using much less propane. The blower can help in the mixing, though, so you can get a more efficient burn and use a little less propane due to that.

A side benefit of using a blower with low pressure is safety. If you develop a leak after the regulator, then there's less pressure to pump propane into your shop, and in this case, less propane will fill it up if you get to the shutoff in time.

In my case, I use my house tanks, and the propane company will not allow more than 5psi, so I'm stuck with a blown burner.



Advantages:
1. The forge can operate a a lower pressure 3-5 psi as opposed to the 8-10 psi my 'venturi' forge needs. Less pressure usually equates to lower propane use.

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