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AnthonyCecere

Building my first forge!

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So I decided to be a bladesmith. The first thing that I find to be important is having the right equipment. I wont argue that amazing works can be made with a file, but I'm lazy. Over the coming months, I'll be building my own forge, 25 ton forge press, 2x72 belt grinder, tempering oven, tool cabinet, and probably some other stuff along the way.

 

I'm very tempted to start with the belt grinder and tempering over. I could pretty much make a ton of good knifes with just that, I imagine. But I digress, project 1; Propane Forge!

 

I've done a ton of research and learned a few things. Things I want to run by you guys as I explain my design choices.

 

First off, I decided that the thickness of the metal encasing the forge is less important and it wont really get too hot if properly insulated. *except around the openings. So for the body, I'm going with .03" sheet steel tac welded to a fame of corner bar. As far as the door, imagine the whole thing as a block with the last 2.5 inches cut off, reinforced if necessary, and hung to another reinforced plate with 2 hinges.

I'm going with a magnet and metal rod to open it and keep it closed. I figure I'll also put a harder holding hook on there when I wont be using the door, but rather the door vents.

 

As far as insulation, I'm going with 2 inches of high temp ceramic wool and about .5 inches of high temp refractory. The floor I'm planning on lining with fire brick (2.5 inches) and about .5 inches of casted refractory.

 

I am going to make the total inside area right around 800-850 cubic inches.

The inner chamber dimensions will be 17 inches deep, 8 inches wide, and 6 inches tall.

 

I plan on have a removable ceramic board wall dividing the chamber in half for the 95% of the time when I'll be using only 1 burner.

 

I'm going with 2 venturi burners running on propane.

 

For the vents, on the door I'm planning on a half circle 6" wide and 3" tall and on the back and dividing board, half circle 3" wide and 1.5" tall.

 

That's pretty much it. What do you guys think?

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If you're going to have a .5" cast floor, you don't need, or really want, a brick floor. That design will just make your forge slow to heat and less fuel efficient.

 

Look up vertical forges here and elsewhere. A long forge makes you heat the ends of blade just to heat the middle, which leads to grain growth and burning the tips of blades. A long horizontal forge is good for heat treating and welding, but less so for everyday forging. Which is why many of us build a couple of forges.

 

Heat treating and tempering are two separate processes. It's hard to achieve stable tempering temps in a gas forge. I use a 3rd hand (we bought it used, and used it in the kitchen first) kitchen oven for tempering.

 

Just my .02

 

g

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I plan on building my tempering oven out of ceramic board, electric heating elements and an electronic control board to regulate the temp. I wont be able to program it but I can baby sit and time it. The temp will be accurate and controllable. The floor is 8 inches x 17 inches. When divided into single burner mode, it will be 8 x 8 inches.6 tall with the burner centered in the middle of that space. Is the cast floor still not good?

Edited by AnthonyCecere

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I find that a kitchen oven is sufficiently controllable, once you get it calibrated. The first several times I used cheap oven thermometers, 3 of them, to calibrate. One high in the back, one in the middle, one low in front. Once you know what the correction is, it works pretty well. I have an electric HT oven, which can be used for tempering, but only once it's cooled down. In those cases, I do a short temper in the oven, cool the kiln down to the temp I want, and do a couple of long cycles there.

 

Hard surface material is mass which has to be heated before the forge is at a working temp. I had a welding forge with a brick floor. It took 15-20 minutes to come up to temp, whereas my vertical Kaowool and ITC forge heats in about 90 seconds.

 

The closer the forge is to the size of the material being heated, the more efficient it is. Unless you're making axes, 8x6 is a big space. OTOH, you do want some flexibility, so a bit more space than you need most of the time, comes in handy.

 

Geoff

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Thanks Geoff. The thing I like about my design is, because I plan on doing this full time, I like that once the forge is heated, I can reduce the fuel to a more sustaining consistent radiant heat. And personally, I do not like the vertical forges. I'm making venturi burners. Most of the research I've found shows that about 400 cubic inches is in a good area per burner. One could go much higher but lose some fuel efficiency, I imagine.As far as the space, I do worry that it's a little wide. I might consider maybe 7x7x17 @ 833 cubic inches, but I wanted the width to be able to work multiple pieces simultaneously. Perhaps have a damascus billet going while also forging out something else, etc. I feel like the 8x8x6high chamber is symetrical, and if properly vented, with the burner centered, it will be a little work horse. The second chamber will be more or less for swords and drawing out large billets. Honestly not my thing, but I imagine good to have.

 

I'm mostly curious about what you guys think as far as, is there any reason this couldn't be a good working forge? Is that enough insulation for .03 sheet, will it be able to reach and sustain forge welding temperatures, IS IT SAFE? Are the vent holes big enough...is it majorly flawed in any way beyond personal preference?

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The shell of the forge is only there to hold the insulation in place, so you're fine with the thin sheet. It will get too hot to touch, but they all do that after a while.

 

As for the door size and whether or not it will reach welding heat, that depends on how you tune the burners. Venturi burners need to be balanced to the size of the forge, which may mean you will need to open the doors sometimes. That's why a lot of people use thin firebricks sliding on angle iron tracks as the doors. If you were to use a blown burner you wouldn't have that issue, as they can run with more back pressure. Too much back pressure on a venture and they don't work.

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Thanks for the advice!

From my research, the venturi burners need about a 7 to 1 vent. By my math, i'm good when running 1 burner but the point you made has me thinking that the vent on the back chamber should be as big if not bigger than the front when running both. I'll probably also have to do some tuning when I switch between single and double burner. I'll try the half circles, if I'm not getting the correct air flow, I'll cut them out to rectangles and just expand from there if necessary. I fear that if I start out too big, i might miss out on a nice butter zone in tuning.

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