[AT] A long shot--Wisconsin part Brazing and cast iron

[Mike Reggie]

  Sure John, The method I use after I've sanded and cleaned the parts is to 
apply the flux,I prefer the paste type, usually with an acid swab to all the 
areas that will be brazed, the same way you would apply soldering paste to 
copper plumbing pipes you are about to sweat.  I always have a tub of 
brazing flux on hand,[I always get the white flux so it can also be used for 
silver slodering as well] and it doesn't matter if sits around and gets old 
and dries up, all you have to do is add water and mix it up, I actually tend 
to over-thin it so it spreads well and is easier to get in all the joint 
areas.
I always pre flux the parts weather I'm using the flux covered rods or the 
bare ones, the only difference being that as I'm flowing the rod into the 
joint, I'd be periodically dipping the bare rod into the flux. I guess the 
powdered flux is ok too, just not as easy to use. I've heard older guys 
talking about using ordinary borax as flux, but I've always had good success 
with the way I do it so I  stick with it, and that is the method I use no 
matter what the materials are, stainless, brass, cast iron, steel, copper, 
etc. In fact, this very afternoon I had to  machine out and counterbore a 
cast iron pump endbell, turn and fit a stainless steel sleeve and braze it 
in, and I did it as I describe above  with very satisfactory results.

  Again, try to keep in mind that what is happening in the joint is 
dependent upon capillary action more akin to sweating plumbing pipes, 
nothing like gas welding muffler pipes.

I hope this helps ....... Mike





----Original Message Follows----
From: John Wilkens <jwilkens at eoni.com>
Reply-To: Antique tractor email discussion group 
<at at lists.antique-tractor.com>
To: Antique tractor email discussion group <at at lists.antique-tractor.com>
Subject: Re: [AT] A long shot--Wisconsin part
Date: Thu, 29 Jun 2006 08:30:05 -0700

Thanks for the information Mike.  Hope you won't mind one more question..... 
   I've only just used the flux-covered brazing rod.  What method would you 
use to use "plenty of good flux?"  How and when do you apply it?  Is it the 
usual powered flux that you would dip your hot brass rod in?    John




At 11:52 PM 06/28/2006, you wrote:

>  John:  I might be able to offer some information on the rubbing of the 
>carbon stick on the weld.
>
>If you've ever had a nice fresh cast iron weld crack on you, you will have 
>noticed that it doesn't crack on the weld itself, it cracks on either side 
>of the weld.  without getting into all the science as to why that 
>happens,[I've tried for years to understand it] it is basically because the 
>heat of the weld draws the carbon from the surrounding part of the metal to 
>the heat zone of the weld, and causes it to crack. So the theory was that 
>the carbon would help to fill in at the spots it was being pulled from, 
>this is also the reason for the pre and post heating, and burying in sand 
>or lime, etc.
>
>  I do all kinds of welding on an almost daily basis, and a part of that is 
>sometimes cast iron, some of it with stick, and some of it with heli-arc, I 
>dislike it very much, there have been really great products developed in 
>the last 20 or so years for cast iron welding, but its whole purpose is for
>repair, I have never seen it as a means of normal cast iron joinery. No 
>mater how much I've done, or what I see others far more talented and 
>informed than myself do, I just can't seem to get comfortable with the 
>whole idea of cast iron welding.
>
>That being said, my preferred method for the repair of cast iron is 
>brazing, be it with brass, silver, or with cast iron filler, it just seems 
>to "work" better. Just remember, clean, clean, clean, and plenty of quality 
>flux, and of course never forget that brazing is dependent on capillary 
>action, it is not a soft weld.
>
>  This is just my opinion, I hope it is of some help   ........ Mike
>
>





                    In the wide-open spaces of NE Oregon



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