Coffee Can Forge Problems

Discussion in 'Hammer & Tongs' started by Tim_1, May 7, 2016.

  1. Tim_1


    May 7, 2016
    So I`m trying to get into making my own knives, in addition to some other metal working projects. To this end I tried to make a coffee can forge. I found some online instructions, and thought I did everything correctly. I used a 50/50 plaster of paris and sand mix to line the inside, and put the torch in at an angle.


    I tried to test fire it, but it never got warm. Instead, after a few minutes, it burst into fire. When I removed the torch, the forge was letting off a grayish gas.

    Any idea what I did wrong? I thought I had done extensive research, but maybe theres something obvious I`m missing? Could the torch just not be powerful enough?

    Thanks in advance
  2. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    There are so many issues:
    1) The refractory needs to be cured and the fired to release all moisture and=nd become a solid insulating mass. This requires running it at low heat for a wile.
    2) Sand and plaster is better than no refractory, but not by much. You really need a layer of insulating mineral wool ( ins-wool, kao-wool) with the refractory over that. The total should be a bit over an inch thick. Satanite is a far better refractory.
    3) The torch you have may be far too weak. It takes a robust torch to run a forge. The old JT-7 was the standard, but now it has been replaced with a newer model. Many buy the their burner from Atlas forge.
    4) While it seems like a cool idea, a coffee can forge is pretty poor for knifemaking. Spending a little more and building a proper forge will be a far better investment. Look at the stickys and see how they work.
  3. Tim_1


    May 7, 2016
    Thanks for the feedback, like I said there is almost certainly something I`m missing.

    1) How do would you run it at low heat? Would you stick it in an oven, or would it need to be warmer?

    2) So I looked up those materials, would it be a layer of ins-wool with a layer of Satanite, or vise versa?

    3) I figured the torch was too weak, I just found it in my garage. I cannot seem to find a "JT-7 torch", no results on google. Care to explain what that is? I would love to buy an atlas forge, they look so
    nice, but I`m a student, so money is very tight. Part of why I like the coffee can idea is that I had the materials already.

    4) I would love a link to a better forge. I assume you are referring to these two pages? I missed those when looking, I guess thats what I get for learning from YouTube.

    Thanks again for the advice, I guess I`ll spend this week gathering the stuff and try again.
  4. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Get with Charles at Atlas Forges for info on torches. He now makes and sells several sizes of burners which come complete with the regulator and hose to connect to a 20# propane tank. These are very low cost. He might even still have some of the old torch type ones that hooked to a disposable bottle.

    The threads you linked to should show you how to build a forge. It doesn't need to be big or have a heavy pipe as the shell. While a larger forge and PID control are great, you can use all the same info and make one from a large metal can or even a trash bucket. High Temp Tools and Refractory sells everything you will need.

    To cure the refractory, first let it dry a few days. Then put the torch in the port and run on low for a good length of time - 15-20 minutes is normal. Increase the heat slowly over 5 minutes until it is running full blast. Run there for 5-10 minutes and the refractory should be sufficiently fired.

    BTW, when using a propane torch, the torch usually does not stick in the forge, but sits just barely outside the hole.

    Baking it in an oven would smell and release a bunch of steam ... it would not endear you to the woman who uses the oven for cooking.
  5. Evan Miner

    Evan Miner Maker

    Nov 24, 2011
    so the problem i see with your torch.
    1 the torch is probably to small as stacy pointed out already.
    2 the flame you have coming out of your forge after a few min. or seconds, is caused buy the canister laying flat on its side. elevate your forge so that the canister is more vertical.

    forge constrution i played around alot when i started out with coffee can forges for the perpuse of heat treating simple steels. and a few things i learned using an under sized torch was to decrease the size of the front to help keep heat in it. the last one i built the opening was just big enough to slide my blade in and out with enough clearence for the needle nose pliers i was using to hold it. now my forge worked for what i wanted it to and that was about it, it would heat up just hot enough to heat treat 1084 and 5160 but to do anything else it was just about worthless. since then i have built my self a decent forge out of a old propain tank. i would recommend saving a few dollars and pick up/order the materials to build a proper forge. below is the adress to find a real siple fairly inexpensive forge.
  6. kn4wd


    Jan 20, 2014
    plus 10 on stacy's comment. I own two of the atlas minis. they are great forges and don't break the bank. you can forge weld in them as long as you take the time and follow the rules.
  7. Talmin


    Mar 4, 2013
    While I have no direct experience with Atlas Forge products, I can tell you building a solid comparable forge will be close to the price of one of his forges if not more.

    I just finished up building mine and it end up being a lot more expensive. Unless you like to tinker and do it yourself for the sake of doing it yourself I would buy one of his.
  8. aarongb


    Nov 2, 2007
    I've tried to make a few small forges, starting with the coffee can. I think a 2-brick is a lot easier to make properly, my first one needed 2 soft firebricks, a spoon, and whatever benzomatic torch was closest to the back door. Then made 2 others like these, the prototype of the Atlas .

    For a burner, the Mag-Torch MT245C was the best off the shelf and least expensive, but I don't think it will heat a chamber as large as that can. Since this seems to be an Atlas infomercial, the Atlas burner is a really good burner.
  9. Kevin McGovern

    Kevin McGovern

    Jul 31, 2015
    I made a coffee can forge using a Vermiculite (garden area at home depot) and furnace cement thinned to melted ice cream consistency in a 4 to 1 ratio (4 parts vermiculite: 1 part cement). This makes a MUCH better insulator then sand/ plaster of paris. You do need to let it dry out for at least a week, and then cure it with a heat gun to get all the water out SLOWLY. Otherwise it will bubble. I heat treated maybe 20 blades in it before i burned out the liner opposite the torch. I believe i overheated it, by closing off the back and front holes partially to contain the heat. It can be used to effect a good heat treat on 1080, but it takes some skill to know where to keep the blade moving to evenly heat it. I'm glad I built it, as it got me started, and i could see what was going on with the steel (am I the only one who loves to see that shadow move through the steel?) I am currently building an electric oven, but my old forge will hold a place of honor in my shop (on a shelf).

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