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How hot does charcoal get?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Chiro75, Sep 23, 2002.

  1. Chiro75

    Chiro75

    Feb 4, 1999
    This has probably been asked before, but I'm still trying to work it out so that I can heat treat this blade. 5-6" long, 1/8" thick, so not huge. 1084 steel. I've HT
    d 1084 in the past without any problems, but I won't be able to get a good even heat with my current setup on this knife. I wanted to hire someone to do a Japanese style clay HT, but I think it'll crack. I should stick with a good 'ol oil quench on this one. Anyway, what I am trying to do is figure out a quick and dirty way to get a nice, even heat over the whole blade. Will firing a bunch of charcoal (regular barbecue stuff) in my grill get hot enough to get 1084 to critical temp? I don't want to have to make a forge, buy a bunch of equipment, etc, and this is about the last idea I have for getting a good even heat. What do you think?
     
  2. Bart student

    Bart student

    676
    Nov 17, 1999
    Yes, charcoal will get hot enough, but the clue is to keep the blade moving in the fire and thus create an even heat. I used to do even khukri's in charcoal fires.. but now I use a gasforge... mucho easier

    greetz and take care, Bart.
     
  3. etp777

    etp777

    Aug 12, 2002
    If yo'ure gonna use charcoal and need lots of heat, grab an airbrush compressor or even a hair dryer, and use that as a blower to get the fire really hot. That's what I'm doing now, but yeah, a real forge will do ya better.
     
  4. Mark Williams

    Mark Williams Moderator

    Nov 28, 2000
    Make a quick and dirty forge in a hole in the ground.Dig a trench and lay a pipe in it that you can duct tape a blow-dryer to it.Make
    the trench go down at an angle. Dig a firepot hole at the other and of your pipe, like a basin.Crush up your charcoal a bit and dump in the hole.Light your charcoal and let it burn down. Turn on the blower and it WILL get hot enough to get it to critical PDQ.You may want to block off some of the airflow into the pipe or use a variable speed hair dryer.
    Dont use galvinized pipe!

    Mark
    edited for speeeling
     
  5. Chiro75

    Chiro75

    Feb 4, 1999
    Thanks for the replies, guys. I may get a chance to do it today. I iknow this is far from an ideal way to bring a knife to temp, but it's probably a one-time thing. If I do more knives this size I'll make a more permanent solution no doubt. I'll keep you updated on how it works!
     
  6. Phillip Jones

    Phillip Jones

    551
    Oct 4, 1999
    Let me add to what Gouge said...

    Don't place the blade directly into the burning BBQ charcoal. Get yourself a pipe just big enough to fit the blade into and bury it in the burning charcoal. This will keep the blade out of the charcoal and you will be able to see the color of the heat and better judge critical temperature. Make sure one end of the pipe is sealed and place a small briquet into it to help create a reduceing atmosphere.
     
  7. Guy Thomas

    Guy Thomas

    Feb 1, 2000
    Steve, you may already know this but don't use the charcoal briquets. Try to find real charcoal, sometimes Wal-Mart carries it. As far as getting hot enough, well every one else has already answered that. Remember, charcoal was the fuel of choice through most of history for most bladesmiths and blacksmiths too.

    For a relatively easy to make, compact forge check this out:

    http://www.customknifedirectory.com/CKD_TutorialFrameset.htm?CKD_Tutorials.htm~tmain

    Tim Lively sells these kits,(sans blower) but they aren't hard to make. You can use his clay and wood ash mix for the refractory or come up with your own recipe with a little research. Fireclay and silica sand would work too. I know you don't want to fool with building a forge to do this one knife, but this little forge is nifty and seems like a great thing to have around. I have the parts for one sitting in my garage, now all I need to do is find a little time!
     
  8. Reg ELLERY

    Reg ELLERY

    934
    Jun 22, 2002
    Just a couple of traps to watch out for with carcoal.

    Unless you get a big fire going you will need to blow air through the charcoal to get up to heat. Not a lot of air but some the more air the more heat.

    Once you have air going through the charcoal 2 things keep a fairly close watch on what you are doing. I have been caught a couple of times after a forging session you get to talking or dreaming the next thing you looking the fire and your blade is sparking like fireworks that is the steel being destroyed and a hole forming I the blade.

    The science of the next thing is possible or may be old wives tail.

    If you leave the blade close to the air comming into the bottom of the forge that is the hottest part of the fire however I have been told that the air and heat tends to burn the carbon out of the surface of the blade a bit like an oxy cutting torch. I tend to keep the blade up a bit in the fire just incase.

    I am an amature so If there is any real blade smith or metalergist out there purhaps you could put me straight on the second (carbon) part. Sometime fairy tails are told to blokes like me and I believe them.
     
  9. Alarion

    Alarion

    Nov 26, 2001
    I once tried to heat a standard screw on iron arrow point to forge it into a broadhead (I was young and fool). I put it in a stove in hot coals, covered it in more coals, stuck in a bellow and started pumping to get it as hot as I could. I was there pumping for about half an hour, everything was a searing white hot, then the point seemed to shift and fell down, or something like that.
    I tried to recover it after the stove cooled down. Emptied the stove, rummaged through the ashes with extreme care but couldn't find any trace of it. As I see it now, I probably got the small lump of charcoals surrounding the point so hot that it simply melt...
     
  10. Reg ELLERY

    Reg ELLERY

    934
    Jun 22, 2002
    Alarion

    I know that feeling.
    The end of a blade does the same thing it happened to me.

    Just a suggestion for the beginners grabb a bit of metal rod or flat bar scrap and have a go at burning it it will give you an idea what to look for.(just a bit of quarter rod should go easy) You will see the metal start to give off sparks as it starts to burn not long after that it falls to pieces all together.

    Just be carefull safty glasses, and whatch out for pieces falling off
    as you pull it out of the fire.
     
  11. Scott Fulford

    Scott Fulford

    91
    Feb 16, 2002
    Dont be afeered to try the japanese heat treat,you can do it.
    Youre using 1084 which is probably one of the best steels to work with regarding temperlines.Before I really got going in knifemaking I used to grind lots and lots of old files(w-2) this process worked well with them and does an even better job with 1084.
    Go to the hardware store and get a little tub of red-devil furnace cement,[​IMG]
    mix a bit of the funace cement with some water to make a slurry a bit thinner than a milkshake,apply it to the blade and let it dry(you can hold the blade over an oven burner to help speed the drying)
    Now take a bit more furnace cement a add just a wee bit of water,you want it to have the consistancy of toothpaste,use a toothpick or a small paintbrush to apply the slightly thinned furnace cement to the blade in little ribs that etend from the spine to just short of the edge in a tapering fasion:
    [​IMG]
    Glob on some more cement at the spine of the blade,about 1/8" thick and let the cement dry completely,dont try to force it to dry,just let it happen overnight.
    When it`s nice and hard heat the blade slowly in your charcoal fire,use a hairdryer to force air into the coals and use a magnet glued to the end of a stick to check the temp,the whole blade should be a nice full orange and the magnet should not stick to the blade,get the coals a wee bit hotter and quernch the blade in a container of vegetable oil thats hot enough to be uncomfortable when you stick your finger in it(should be about 130 to 140 degrees)
    most of the cement will crack and fall off in the quench but if it stayed on for more than a couple of seconds(and it probably will) it has done it`s job by not allowing the steel under it and around it to cool fast enough to harden.The wavy temperline you will get will not exactly follow the pattern of the ribs,compare the photo above and the one below and you`ll see what I mean.
    [​IMG]
    go back to the grinder and remove the remaining cement with a 220 belt,continue with finer grits until youre close to the finish you want,you should start to see the temperline at the 400 grit stage,when ever youre happy with the finish mix up some ferric chloride (PCB etchant from radio shack) with 2 parts water in a cylindrical container(preferably glass) and let it sit for a few moments(stay with it and watch) you should see the temperline become much more visible,start hand sanding with finer and finer grita with a ferric chloride bath in between grits with shorter and shorter soak times.It really will look good.
    The knife in the above pic was not hand polished but it`s the only pic of a blade I had used this method on that I have right now.I used a zinc phosphate coating on this blade and it reacted differently with the varying hardness zones.
    Good luck and let us know how you did.
    Scott
     
  12. tmickley

    tmickley

    Apr 4, 2001
    Scott, have you tried anything else for getting a hammon besides the Red Devil furnace cement?
     
  13. Scott Fulford

    Scott Fulford

    91
    Feb 16, 2002
    No,tmickley I`ve only used the furnace cement.it gives fairly good results when it doesnt crack and fall off in the quench prematurely but I`ve found that if you let it dry completely and use the light wash of cement to coat the blade first it usually hangs on long enough to do the trick,I`ve seen formulas for mixing clay with iron filings ashes and so forth but I`ve never fiddled around with those,have you?Let me know if you know of a better substitute,I like making blades with temperlines and I appreciate all the help I can get.
    Scott
     
  14. Reg ELLERY

    Reg ELLERY

    934
    Jun 22, 2002
    Great instruction tanks for the tips.
     

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