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Ser Menalak

Correctly heating iron

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Hi guys,

 

So I have been blacksmithing for a few months now, only about an hour or two every few weeks because of school. Every time I run into the same problem and every time I tell myself it'll be different. I have a very hard time heating what I put into the forge correctly. Today I was making a hook from 3/8 square stock and at one point I burnt off the end. It seems to always happen. As such I'm scared of keeping it in the forge long enough to even get a decent heat. I have a brake drum forge so I typically have to stick it into the coal at about a 45 degree angle due to the edges of the drum. I am also using a hair dryer which I suspect is blowing wayyyyy too hard. When I took my blacksmithing course at a shop I never had this problem it seems to just heat the iron evenly and with minimal to no burning. Does anyone have some tips for someone with a brake drum forge (other than to get a real forge) to prevent burning but obtain a nice high even heat? Thanks.

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You need to find a way to control your air flow.  If you are using a blower such as a fan (of many types) you need to regulate the flow with a blast gate (air gate), speed controller on the fan motor, an adjustable baffle or diverter, or any other means of flow control.  Sounds like you are running the air flow full blast.  If you are using a hand-cranked blower...quit cranking so fast!!!  :-)

 

I use a sliding blast gate (air gate) on my brake drum forge with 2" black pipe plumbing and only open it 1/4 to 1/2 to heat most things.  Rarely do I open it all the way.

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Okay, there are a few things might be the problem besides just needing experience. Placing your work into the forge at a 45* angle is crossing the burn zones rather than finding the "sweet spot" the spot where the heat is hottest and the oxygen has been completely consume and is even across the pot. Somewhere here Glenn has posted a good graphic of the zones in a coal fire. Nearest to the air grate is the oxidizing zone where the oxy in the blast air hasn't been consumed by the fuel. Up from there is the neutral zone where all the oxy is burned up and the temperature is at it's max. THIS is the sweet zone. Next up is the carburizing zone, all the oxy is gone from the blast but there is still more than enough heat to gassify (pyrolize) the fuel and it's components. It's still a good hot zone but not really hot enough to do much forging, bending and truing up yes but forging needs more heat, this is the red zone heat wise. It's called the carburizing zone because all the free carbon released from the fuel at this heat with can bond with iron/steel, etc.

 

There are a couple easy solutions: First simply lay your steel in the fire more horizontally. Second fill the drum partially with something non flammable to raise the burn zones closer to the drum's rim. This would be my choice. Third would be to replace that drum with a shallower one. It's pretty common to try using too large a brake drum, even a pickup truck drum is kinda large for most beginner projects. A Prius brake rotor is small and shallow enough they work a treat. Filling  the drum doesn't need to be fancy or special, clay out of the back yard works just fine. You can trim up fire brick too, just leave room around the air grate.

 

The other solution is controlling the air blast and there are a few easy ways to do that too. Blow driers are free air compressors meaning there is no positive restriction or mover for the air, fan blades. So, you can block the air flow on either end, intake or outlet without overheating a blow drier. This is NOT true for all blowers, if the motor relies on air moved by the blower for cooling you can burn it up by blocking the air flow. Blow drier motors have their own vents and impellers so blocking the blower isn't going to hurt it at all. Blocking  the output works very well but it a little harder to build, not a big deal but it is a little harder. Than THIS, blocking the intake is as simple as putting a Post it note over part of the intake port. The niftier method is to make a little swing gate, just a little disk on a pin so you can slide it around to open or close the intake ports.

 

Diverting the air is probably as simple as it's possible to get, just aim the output of the blow drier away from the pipe connecting to the air grate by as much as you need to get he correct flow.

 

Putting dimmers on motors isn't as simple nor safe as it seems. We have professional electricians and more than one accident investigator here who are death on the idea unless you know exactly what you're doing. I won't go any farther than to say it's not a recommended practice by the guys who KNOW what they're talking about.

 

Frosty The Lucky.

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How big is your fire? Even thou it's counterintuitive sometimes a bigger fire is easier to work with because the sweet spot is larger. I've seen many beginners run too small a fire due to either timidness or fuel conservation. A gentile correctly sized fire (see the blast control comments above) is a pleasure to work with.


We were typing at the same time Frosty!

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You need a fire ball the size of a melon minimum. That is the yellow zone in the photo. Larger stock requires a larger fire ball. You want the fireball covered with coke, and the coke covered with fresh new coal.  

 

Fuel does NOT control or create the heat, AIR controls the heat. More air and you get more heat. No air and the fire dies out.

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I used a smallish brake drum and then put a taller piece of sheetmetal bent into a C right inside the edge of the drum to get a deep forge you could put metal in horizontally right in the middle of the fire without knocking coal/coke off the edges.  Cut a mousehole opposite the opening to run long pieces across and out of.

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Break drums are misurable, there are a lot of beter setups. In my openion what got every one started on break drum forges was the olf breakdrums that were riveted to the hub. This gave you a convieniant botom blast forge pot with little modivication. To day the only breakdrums that are built that way are trailer drums. (Knock out the baring races). Honestly, the work to make one work right makes bulding a diferent forge practical. Might i recomend either of Glenn's 55 forges? Particularly the sideblast. Tho the use of a rear break disk seems to work well.

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