one brick forge questions

S

Sharp_newbie

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Aug 12, 2007
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i made a one brick (well technically 5 brick) forge out of 5 pieces of fire brick i bought. with this purchase i also bought a propane torch (a benchmark, nothing special) the forge was made by tying the four pieces together with wire (made a square basically, with a hole in the side for a propane torch and three 1/2 inch holes in the back for ventilation) i tested it out on a small piece of steel and found that it only got the steel cherry red when i placed the steel in the path of the flame. and cooled down as soon as i pulled it away.

so my question is...

how long should i heat the forge before i stick the knife in? the first attempt i was a bit excited to try it so i did go a bit fast and just fired it up waited 15 minutes then stuck in the steel.

just curious to know if i need a better torch (more heat etc.) or do i just have to wait longer for the forge to heat up.

i realize that it would be easier to explain all of this with a picture, but sadly my camera's USB cable is MIA...

im writing this on my way out, if the topic has already come up please re-direct me
thanks
 
how big is your chamber. you might need 2 torches
 
Yeah, it is kind of difficult to visualize what you did with the brick setup. Most one or two brick forges use a single brick to create the forge chamber with a second brick optional to extend the length. I used a 1" spade bit in a hand drill to bore a couple of holes (one on top of the other) into a soft fire brick most of the way through. I used a file to connect the holes into one chamber. Then I used the same drill to punch a hole in the side of the brick towards the front top at an angle pointing slightly towards the back. I rounded the chambers top and bottom to make basically an oval so the flame will swirl better. The torch should not be placed directly in the opening, but an inch or two away to allow good combustion and plenty of O2. I experimented with several bricks, and this was the best setup for me. I used other bricks to place on bottom, top, and around the forge brick to insulate and provide structural support.

The brick takes the heat and re-radiates it into the interior of the forge chamber. This is what allows the heat to build. If you're not getting enough BTU's into the forge, the only way you'll be able to heat the steel is by placing it directly in the flame. At first I used a basic MAP gas torch and found I wasn't getting hot enough. So I switched to the JTH-7 Bernzomatic torch many recommend. I used an adapter to a 20# propane tank, and can adjust the flow on the torch to control temp. It gets more than hot enough to effectively heat treat O-1 (1450+) and other basic carbon steels, but it's not going to get hot enough or have even enough heat to heat treat stainless or long soaking steels or forge steel effectively. I use a home built oven for my heat treats now, but like I said, the brick forge will work for steels with HT criticals of 1400-1800 degrees and shorter soaking times.

Make sure you constantly move the blade in and out to get the heat evenly distributed because many one brick forges have bigtime hot and cold spots.

Here's a bad pic. It's been out of use for a while here, and the bricks on top were used in other projects. The torch tip is maybe a bit far away, as the bricks have been moved somewhat. The flame hole is where the tip of the torch is pointing, just in front of the brick on the right side of the chamber.

IMG_3634.jpg


--nathan
 
man you got enought bricks there to make a heatreat oven ;)
 
hummm... i might need more heat then, my one brick fore is not too big as the pieces of fire brick i used are flat roughly 9inch by 4 inch by 1 inch so all together the forge is not overly big, i would say as big as the brick with a hole in it in your picture silver_pilate... i do have access to an asetiline torch at the shop i work at... i might try that for heat, or i could buy another torch... back to the workshop it goes for now

i will try to find my Camera cord so i can post a picture for tomorrow
 
For all that work you should try coal, it's white hot in 15 min. :D

Here's an old pic of my primitive setup. It was really just a pile of bricks that I stacked however I wanted for the size work I was doing.
 

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I can't view the pictures you have posted, but from the size of the bricks you mentioned it sounds like you're using the hard firebricks, not the soft refractory bricks. The hard bricks don't provide enough insulation.

Get several soft refractory bricks from here.

You also need a better torch. I tried to use a regular plumber's torch, and it got hot enough to heat-treat a very small blade, but just barely. The JTH7 is a million times better--I was blown away when I tried it.

This forge design is also a lot better than a one-brick forge. It uses two soft bricks. With this forge and a JTH7 torch I've managed to heat-treat a 10" bowie knife and also forge some hunting knives. Right now I'm using it to heat-treat 3" to 4" blades until my real forge arrives from Darren Ellis. :)

Josh
 
For sure, hard bricks won't fly. The soft bricks are soft enough to shape with your fingernail, and they are much better insulators, even if more delicate. That britishblades forge looks pretty good as well.

JT, if you can't tell, I've already built the heat treat oven :D. The brick stacked on the top left of the picture with grooves in it was one of the oops I made while carving out grooves for the heating elements. I bought a case of bricks about a year before I built the oven. They sure came in handy.

--nathan
 
I agree, it sounds like you're using hard bricks, they just won't do for your forge. I'd pick up one or two soft bricks from Darren for just a few bucks and do it that way.

If you're going to order soft bricks from Darren, you might as well consider doing a coffee can forge instead and just ordering some inswool and satanite.

The regular plumber's torch will work fine with a 1-brick, but they are painfully slow. If you're normalizing and heat treating, they use a ton of fuel to get the job done.
 
Yes I think the burner BTU's & forge chamber voluem is the key to this thing, it is bordering on underpower to begin with, I have not been able to reach heat with your basic plumbers torch.
Cheers Ron.
 
I have to agree with others, your forge chamber is way too large for the torch your are using. I am running a '2 bricker' using 2300 degree Farenheit soft fire brick with a chamber 2.5" in diameter by 7" in length. The chamber is coated with ITC-100 and I use the Bernz-O-Matic torch and can almost reach welding heat. I can start heating steel in 5 minutes or so, however, the forge gets to a real nice working heat after about 30 minutes. After that point, the blade gets back to forging temp in about 3 minutes. Good luck...
 
Is there a "rule of thumb" as to how far away the blade metal needs to be from the heat source?
 
sharp,i made a 2 can forge with 2 jth7 torches lined it with kaowool. i used a coleman tee i got from wal-mart. it gets verry hot and is plenty big. with it hooked up to a 20lb tank i get many hours before it needs refilled....willy
 
MitchDad,
To answer your question about how far away to keep the blade: I don't really know (I am a newbie at this!). However, man has used charcoal or coal for ages to forge metal and the blade is right in there. I think the important thing to remember is to protect the point and the blade edge from overheating as much as possible. In my little 2 bricker, I elevate the blade so the gas passes around the blade and not directly on it. I found thatif the flame plays directly on the blade you get increased scaling. I also turn the blade so the edge is opposite the 'hot' spot on the wall. This helps to keep the blade edge from overheating. I also will grab the blade with the tongs and slide the blade in and out and inch or so to even up the heat in the blade vs letting one section get too hot. Experiment with blade positioning in the forge, sliding it in and out, resting on the bottom, elevated, etc., till you like the results you get. Good luck.. oh, one more thing.. if you haven't forged at night, give that a try sometime. The 'color' of the steel is very different than in daylight. Some bladesmiths only heat treat at night because the colors are easier to see.
 
Okay, heres a new take to the forge... i do have access to an asetaline torch. would that do the trick for my hardbrick forge? or forget about it... i kindof want to work on the knife this weekend and don't want to wait to order some softbrick, so... can it be done then or no deal wait for the softbrick.
 
Oxy/Acetylene torch flame is about 6300 F and will ruin (read shatter violently) masonry grade brick and likely melt your piece. I'm not a knifemaker as yet, but I have some experience with oxy/acetylene welding.
 
Not to steal the thread but forge related. Willy can you show how you worked the two JTH7 together. I currently use a two brick forge but want to make something just a little longer and bigger diameter, I think that I would prefer to use two JTH7 instead building a new burner.
 
The brick is a fire brick, not a masonry brick I believe.

I'd just order the stuff to do a coffee can forge and run your plumber's torch. It's worth the $20 up front.
 
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