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brazing for dummies

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by dozuki, Nov 7, 2007.

  1. dozuki

    dozuki

    77
    Apr 4, 2006
    I am close to finishing my first knife. Which I might actually show to people. I was wondering if I could braze a brass guard on it with a normal torch. I have a JPH-7 benzomatic. I was hoping someone could give me a bare bones how to or point me to the right site.
    Thanks in advance.
    Paul
     
  2. Bruce Evans

    Bruce Evans

    Sep 26, 1999
  3. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    Terminology - solder , low temperature ,typical solder used for knives is a 95Sn5Ag solder melting at about 400F.When soldering stainless steel make sure flux is specifically designed for it...Braze, high temperature ,1100F or higher .Will require thought about reheat treating the blade after brazing ! .....Bruce should have mentioned in his tutorial that fit is important for proper capillary flow of solder or braze .Gap should be about .003" !! ....When soldering or brazing heat work quickly ,pull torch away , and touch solder or braze to the part .The work melts the solder not the torch.
     
  4. Bruce Bump

    Bruce Bump KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 2, 1999
    I watched the SR Johnson video the other night and was amazed to see him use a hot air gun to solder the guard joint. Its nearly impossible to overheat anything but be sure to use low heat solder (400 degree)
     
  5. Ilovetoolsteel

    Ilovetoolsteel

    Jul 28, 2003
    I saw that, I always figured my heatgun could be used to solder it has 2 temps 650° and 1100°

    I just use the propane torch because it's faster. I might give the heatgun a try next time.

    How did you like the convlouted way he puts the handle slabs on?
     
  6. Mike Mossington

    Mike Mossington

    108
    Jan 1, 2004
    I watched the same video last night. Was very impressed with his use of heatgun - must try that. But I was stunned when he went from 50-grit straight to 400-grit, and ended up with a polish. Who'd athunk??
    And from what I could surmise, he runs his grinder at a very high speed - amazing control when on the grinding wheel!!

    Mike
     
  7. Alarion

    Alarion

    Nov 26, 2001
    1) Do NOT hard braze a heat treated part. Brazing will utterly destroy any HT you did.
    2) Solder it with silver or tin solder, the kind used for rifle lugs and sights.

    3) As Mete said in a very concise way, one of the most common mistakes is to think that the torch melts the solder. This will lead invariably to a poor job, as the torch will melt the solder long before the work is hot enough to accept the solder itself. The solder must wet the work, and this happens only if the work is hot enough to melt it. Another big mistake is heating the work like hell and then use the torch to drip solder on it. On hydraulic tubes it may work, on a knife it produces an unsightly mess. Besides, you'll heat the work too much.
    Just heat the work for a while, then briefly remove the torch and touch a piece of solder to the work: if it melts, you can solder it, otherwise heat it more, frequently repeating the process.
    This is a good way to get proper temp, but requires a good hand and is better suited to soldering where the solder won't be seen, as from behind the guard. You need a tight fit and you must not exagerate with the solder or it will drip through and along the blade making a godawful mess of your knife (don't ask how I know!:grumpy:)

    3) To solder a guard from the front side, the best way is to take the solder rod or wire, and hammer it flat and thin, perhaps 0.01" thick. Cut two little bars out of this, long as the blade is wide, and about 1/16" wide and lay them 45° between guard and blade (the guard must be kept against the blade in one way or another. The knife must be tip up in a vise. Heat the tang and the lower part of the guard with the torch, being careful not to let the flame go over the upper edge of the guard. Let the pieces soak the heat in SLOWLY (use a low flame) and watch carefully for the solder to melt. As soon as the solder melts, remove the flame.
    The solder will be sucked into the junction by capillary action, and leave a very clean weld. You can spray with water or let air cool.
    The thinner and tighter the junction, the less solder you'll need, the stronger the bond will be, the cleaner will be.
    Do not rush things either fitting the guard or doing the soldering.
    Silver solder is hotter-melting than tin weld. Both work very well.
    Careful and slow are the keywords.
    You may need as much time you needed to make the blade just to fit the guard, or even longer, at least initially, but it's well worth it.
     
  8. Bruce Evans

    Bruce Evans

    Sep 26, 1999
    Mete,When I made that tutorial I wasnt thinking about the blade guard fit,it was mean to show how to clean up a already bad solder job,I was thinking people would already know how to solder...

    I am also going to try the heat gun approach.
    Bruce
     
  9. dozuki

    dozuki

    77
    Apr 4, 2006
    Thanks for the tips. I'm going to give it a try soon. Hopefully the results won't be to godawfull.
     
  10. Alarion

    Alarion

    Nov 26, 2001
    My weren't, even if I was a complete rookie, as long as I followed strictly the tutorial. Don't try shortcuts. ;)
     

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