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Thread: How about my starter propane/firebrick forge scheme...

  1. #1
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    How about my starter propane/firebrick forge scheme...


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    was gonna get some insulating firebricks, the 2300 degree K-23s ($4-$5 ea). They are 9x4.5x2.4 (or 3"). With about 18 of them I can make a forge that is about 9x18" and 14" tall, would weigh about 34lbs. There would be an opening about 4" square at the front end, down low so that there is a pocket at the ceiling to trap heat. I can just stack them up, wouldn't really need to use mortar. I could make a base w/ handles to set it on so I could pick it up to move it from a storage shelf to a suitable work surface (I have somewhat limited space).

    I like this idea better than using a insulated stove pipe, or a big pipe/bucket lined w/ ceramic wool fiber. I don't want those fibers in the air.

    The object is to heat 1084 blades w/ propane torch to ca 1800f till they stop being magnetic and then pull them out to quench/harden. Not forging or forge welding or anything like that, just stock removal.

    I have one of those propane torches that you use to burn grass growing up from cracks in your sidewalk or whatever, it is a long wand so you don't have to bend over. The length of the wand doesn't matter but the thing makes a big flame and I have adapter hoses to hook it up to a 20lb propane bottle. Was thinking I could set it in place, maybe next to a hair dryer also blowing air into the forge hole. I could get more sophisticated later, mortaring it, using a better torch scheme etc.

    Would my basic scheme work for now?

    Are the 2300 degree bricks sufficient for this?

    Should I make a hole in the other end of it so that and air current can pass all the way through it or something? Would the hole on the back side be down low as well? Or, is only one hole in one end all you want to do.

    Any other low-budget suggestions to improve my basic scheme? Wondering if there is some shorter torch head I can get that makes a big flame like the one I have.
    Last edited by Vulcanite; 07-26-2012 at 09:01 PM.

  2. #2
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    Heat to quench w/ some Fire Bricks and a Torch wand??

    Was going to make a very simple forge by just stacking up some 9" long K-23 2300 degree insulating fire bricks and blowing a propane torch wand into the forge mouth.

    Sole purpose would be to heat 1084 blades up to quench. Just to about 1800 degrees till the magnet don't stick and then shut it off.

    Are 2300 degree bricks sufficient?

    Do I apply the flame directly to the blade or do I make a point NOT to directly flame the blade?

    Would a propane weed burning torch or work-bench torch wand get the forge hot enough? HF has one for $20 that is apparently pretty hot.

    The pics are of a HF torch and a small fire brick forge, similar to the one I might build.




  3. #3
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    for reference, that forge you see is only about 9" cube. I would make something a little bigger w/ a heat trap in the top so the heat wouldn't just roll out past the top edge of the mouth.

  4. #4
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    If that is the way you want to go with making a primitive forge, and you use a weed burner or a torch - you need to make a hole in the side of the forge. Place the burner just OUTSIDE the hole. You will have to move it in and out some to find where it burns the best.
    Tai Goo uses a weed burner forge. Not the best, but it will get the steel hot. His photos will help you see where the hole goes and how to place the burner.
    http://www.customknifedirectory.com/...ad.php?t=41907

    1800F is way to hot for heat treating 1084. You want it around 1500F, which is about 150F higher than non-magnetic. It does not require that you hold it any longer than enough to see that the blade is evenly heated.

    Forging temp for 1084 is around 1800F.

    It is just about as easy to make a simple venturi burner from a piece of pipe and make a simple basic forge from the firebricks as you show them. The total cost is low and the forge will be far more reliable and useful. The forge chamber should be about 4" square by 8-10" long. Forget you idea about a "Heat Trap" in the top.

    You can also purchase a burner or burner parts kit for about the cost of a weed burner. You will need a propane tank with a regulator and a hose, too. High Temp Tools sells all the items needed. The burner, regulator, and hose will be able to be moved from forge to forge as you make new and better ones later. When you are ready for a big step up, and go to a blown forge, these parts will still be of use.
    http://www.hightemptools.com/supplies-mainpage.html

    The stickies have a good bit of forge and burner building info.
    Stacy E.Apelt
    It is better to die fighting evil than to live under it.

  5. #5
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    Um, non-magnetic is closer to 1400°, not 1800°. You want a forge for HT only? I'd go with something much smaller. Two bricks stacked vertically stand 9x9. That would give you 2½" of wall around your chamber. 9x14 would be about one layer of bricks more than you need.
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  6. #6
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    Tai Goo has posted pictures of his weed burner forge.

    My opinion based upon your questions is that you need to spend more time researching forges.

    To start. I'd be more inclines to direct you to buy some Inswool ceramic blanket insulation and find an empty freon tank to build a forge.

    Spend 5-6 hours searching past posts on forge builds and get familiar with the most common methods.

  7. #7
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    Double post....
    Last edited by Brian Ayres; 07-28-2012 at 03:50 PM.

  8. #8
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    I have a weed burner like that. It throws a lot of fire. It would fill that box with flames and have them coming out the front I would think. There may be a way to regulate it some though. I just use mine for burning weeds. If you use that burner pelase be careful. A better type burner might be the one made to screw onto a small propane bottle that has a curved shaft. I think it would make a more concentrated flame. I saw some at my local big box hardware store by the small propane bottles for about $37.

    I do have a very small forge made from a 1 gallon paint can. It is lined with the ceramic wool and then I painted the wool with santite. I use a mapp gas torch, and it gets plenty hot to forge with. It is just limited a bit on what length blade you can heat. 5"-6" would be the max blade length for my forge. The material to build it probably cost around $20. The torch was $50 or so though.

    Just my 2 cents. I am not expert, just be careful.

  9. #9
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    You have put up two identical threads in the same day. I'll merge these, but lets not get excessive.
    Stacy E.Apelt
    It is better to die fighting evil than to live under it.

  10. #10
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    I could tell ya what I did but it may be spending more money then what you would like. I am still playing with it but I took a propane tank and cut out the bottom. Flipped it on its side, lined it with ceramic blanket, and refractory cement. I drilled a hole in the side and mounted a burner that I bought online. I went with Stacys attitude to get a good burner that could be moved from forge to forge.

    I also got a cheapo ducting fan and routed that to the burner, it doesnt have much driving force but helps get to forging temps.

  11. #11
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    OP here,
    I already have one of those weed burners w/ the long curved shaft hat takes a little 1lb propane bottle, though I do have adapter hose to hook it up to a BBQ propane bottle. You think that more moderate flame would be better than the big as flame of that HF torch. I guess we don't want to fill it up w/ fire.

    I stand corrected about the non-magnetic temp for 1084. Thx

    I was basically going to make a forge like the one I posted a pic of but twice as long so I can heat large blades.

    I see that I am to put a hole in the middle of the forge for the flame to to into, maybe at like a 11 or 1 o clock.

    I finally found a place in town that sells these bricks as well as boards and blankets. I would rather use bricks as I don't want to inhale those ceramic fibres. Also, the bricks can be utilized to make a bigger better forge later.

  12. #12
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    You will not have a problem with the fibers if you are A. in a well ventilated area, and B. if you cover them with some sort of coating like satanite of ITC100. it is one of the best ways to do it. don't get scared off by the threat of something easily solvable.

  13. #13
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    INterior volume will be ca 17x7x4"=476" Will be made from 17.3 bricks, about 35lbs. I suppose my little weed burner I alread have will do till later. The 4" long one that talkes 1lb bottles? Does that sound rigght?

  14. #14
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    I have a setup similar to what you're talking about. Using soft, K-23 bricks I built a forge with a chamber roughly 4"x4"x9". I have the weed burning torch that you posted a picture of in your OP, from Harbor Freight. The rear of my chamber has a small slit to allow the flames to fully reach the entire chamber, otherwise the pressure from the torch causes a blow-back effect reducing the efficiency. I just aim the torch to blow straight in from the front. Once I get the torch head situated just right, it takes less than 10-15mins to reach non-magnetic. I like my torch because it provides a very large, very hot blast that works quite well.

    I would suggest building a smaller forge to start with, it will be much more efficient and easier to use. Unless you will be making 17" blades on a regular basis, you won't need that large of a chamber. Many people use a simple 2-brick forge to heat treat knives of a decent size. I would say that for general sized/purpose knives, a forge with my chamber size is quite sufficient.

    I will try to post pictures of mine tomorrow.

  15. #15
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    OP here.

    Thx for the post. I'm get or build a venturi torch thingy later. For now I'll try my luck w/ my litte propane weed torch. If it doesn't have enough ppower maybe I'll get the one I picutred from HF for like $20.

    Thx. One nice thing abotu stacked bricks is that you can re stack to make it smaller or larger, at least while you are experimenting.

    The first knives I'll make will have blades 5-9". What is the longest OAL of a blade/tang you can get away with with a 9" deep forge?

    I'm gonna make a frame base out of 2x4 and 2x2s and some strips of cement board. Sort of like a big tray to set the forge on and to hold it above whaever bench I put it on and that will have grab handle on it so I can carry like a big tray.

  16. #16
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    If I angle the knife, I can get about a 10" OAL knife in there. I used 1/2" tool cloth, like chicken wire, to hold my bricks together. That makes it a nice portable cube and holds all the bricks in place. A little work with some wire cutters and I can redesign/re-stack the whole shebang.

  17. #17
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    Here are a couple of pics of my forge setup.



  18. #18
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    Guys, are 2000 degree bricks good enough for doing the heating for the quench for carbon steels or does one need the 2300 degree type?

  19. #19
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    Thx for the pics and info broomhead. The chicken wire is clever. Good way to hold hot bricks togeyher w/o motar or welding brackets.

  20. #20
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    2000 or 2300 degree firebricks for the quench

    I only need to heat carbon steel to ca 1500 to harden with the quench. Can i get by with 2000 degree k-20s? Local place has box of twenty for $70. They are lighter and better insulater than the greentherm-2300s.

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