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Posted by Prometheus on December 29, 2007, 10:25 pm
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>> Hello all,
>
>> I decided to try my hand at making some damascus-style pattern welded
>> knife blanks, and it's working more or less all right. Just a couple
>> of quick questions for those of you who have done this, if you have
>> the time to answer.
>
>Just a quick note, you might want to pick up Jim Hrisoulas's book 'The
>Pattern-welded Blade' and the video he did. It will answer a lot of your
>questions.
>
>(snip)
>> All that being said, here are the questions I have been asking myself
>> while working on this. The first is a matter of flux- being a little
>> less than completely confident about my forge welding technique, I've
>> been putting about a tablespoon of borax on each time I put the piece
>> back in the forge. As you might imagine, this has made a real mess of
>> the firebricks I've got on the bottom of the chamber. Any clue as to
>> how much flux I *should* be using? It's working, but I get the
>> feeling I'm probably overdoing it a bit.
>
>While you don't have to use Anhydrous, I'm not that happy with 20 Mule
>Team. They seem to have added something to it that makes it stick a lot
>more, which is a pain when you have to wire brush the slag off the anvil
>and the hammer. I got a pail of plain borax from a chemical supply house
>and it behaves like the 20 Mule team I remember from 8-10 years ago. A
>jeweler friend of mine pointed out some changes in behavior of 20 Mule
>Team she noticed when using it as a soldering flux, which lead me to try
>changing my flux. As to the amount, you are overdoing it. You really
>only need enough to coat the piece and it should last through 2 or 3
>heats, after which you should wire brush it off and reapply a little more.
Yes, it is kind of a sticky mess. I thought that was just the price I
had to pay to use a flux in a forge- well, if this one turns out, and
I decide I want to keep at it, I'll invest in a better grade of flux.
It definately helps to know that refluxing after every heat is
unneccessary.
>Also, get a chunk of high alumina kiln shelving to use as a floor to your
>forge. It will take a little longer to heat up, but hold the heat well
>and give your forge a little more thermal stability. It stands up well to
>flux, and when it is finally eaten through enough to be replaced, you can
>just take it out and put a new one in. As to what you have in there now,
>kitty-litter (plain clay type) is good at sucking up the flux you already
>have in there. Then it can be raked out.
I'll give that a try.
>> The second is a matter of gas setting- I can't for the life of me
>> remember if I want more or less oxygen for the best weld. So far,
>> I've been running the mix really gas rich, with a low stream of forced
>> air. Again, it seems to be working all right, it's just a matter of
>> figuring out if I'm making more work than necessary for myself.
>
>You want it rich, but you don't have to have it really rich. Just enough
>so it cuts down on scaling. If you have enough propane (in a non-blown
>forge) that makes it out of the forge door before it burns, you have it
>rich enough. I'm not sure what to look for on a blown forge, but if you
>put a plain piece of metal in, and it doesn't seem to really scale up
>until you take it out, you are probably rich enough.
I don't know if it's because of the flux or the mix, but it's not
scaling at all with what I've got it set at now, and it's plenty hot
until the tank begins to freeze up (I've really got to get my 100
pound tank down to the co-op and get it filled, the 20 pounder is a
PITA!)
>> Third is dealing with small cracks. At this point, after about 3
>> folds and maybe 12 or 13 heats, it's looking pretty good- but there
>> are one or two areas where there is a small crack on the surface that
>> is apparently a spot where the weld did not take fully, as they look
>> like the partial outline of a chain link. Any chance that just
>> continuing to flux the blank while drawing it out will close these up,
>> or do I need to grind those out before proceeding? (they're visible,
>> but not very deep)
>
>There are several reasons these can form. Yes, fluxing and hammering can
>weld them up if they have good mating surfaces (the hammering can really
>help on getting them to mate up). If they are deep, chiseling them open,
>wire brushing them out to get out any slag or crud, and re-fluxing can
>work. If they are shallow and you are pretty confident of that, grinding
>can take care of it. But I've run across ones I though were shallow, but
>ran deep enough to ruin the piece when grinding.
Well, right now I need to do some pretty heavy drawing out, as it's
about twice as thick as I'd like it to be, so I'll just keep some flux
on it and hope for the best. In a worst case senario, it was an old
junk blade beyond any hope of repair, and it's good practice. If it's
cracked, but has a good pattern, I can always use it for inlay.
>> And last, but not least, is bringing out the pattern- it'll be a few
>> days before I really need to start thinking about that, but it never
>> hurts to plan ahead. I have a quart of ferric chloride that I've been
>> playing with by etching copper and brass with it, and I more or less
>> intend to etch the finished blade with that- unless there is a good
>> reason not to. Any opinions on whether this will work better than
>> muriatic acid from the hardware store? I'm also wondering if the etch
>> needs to be done before or after heat-treating the blade- a lot of the
>> pattern-welded blades have a striking black and silver contrast, and I
>> have no idea if this is a matter of heating it after etching, and then
>> polishing the high points, or if the etch itself makes this happen.
>
>I'm not 100% sure, but I think if you've used your ferric chloride to etch
>copper it may copper plate your blade. (quick search)
>http://home.comcast.net/~jeshern/copper.htm
>
>However ferric chloride is a good etch, as it leaves a good contrast and
>does give you a little topography. You shoud do it after heat treating,
>and clean up after the etch with cold water and 600 grit paper to bring
>out the pattern. Don't sand too much, just enough to get good contrast.
Perfect- I'll just make sure to get some more ferric chloride, as it's
pretty cheap anyway.
>> Any hints, tips or tricks would be greatly appreciated. I'm sure this
>> one is going to turn out to be ok in the end, but it never hurts to
>> get advice whenever possible.
>
>> Thanks!
>
>Hope that helps!
Sure does, thanks for taking the time to reply.
> Todd
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