# TIG brazing



## akjeff (Nov 18, 2020)

Gave the TIG brazing a try this evening, and I think it’s going to work out. Needed to join a cast iron knee crank to a steel socket, to make a redneck power feed for the knee of my mill. After doing some research, decided to use aluminum-bronze filler and AC TIG. Had to fiddle around with the amperage a bit, and it brazeded rather nicely. Looks to have penetrated/flowed fairly well. Preheated the parts to 400F, and had the welder set at 120 Hz AC and cleaning action at 90%, with Argon at 15-20 SCFH. 3/32” tungsten and #8 cup w/gas lens. Started out at 40A, which was way too cold, as was 50A. At 60A, it was starting to puddle and flow, but it took longer than it should. 70A turned out to be just about right. Formed a puddle quickly, but if I lingered a bit too long, it would start to melt the base metal ever so slightly. Then dressed it down because A.) it looked terrible! and B.) I wanted to check for porosity and wetting action. We’ll see how it holds up. The drill motor drives the knee pretty well without feeling like it’s working it too hard.


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## matthewsx (Nov 19, 2020)

There's a reason the old timers brazed everything....

Yes it can look awful when you stop burning but when you clean it up and start using it that's what really matters. I had someone teach me how to braze sheet metal for autobody repair years ago and just did some repairs on thicker stuff with oxy recently. 

Proof is in the results and yours look good.


John


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## NC Rick (Nov 19, 2020)

akjeff said:


> Gave the TIG brazing a try this evening, and I think it’s going to work out. Needed to join a cast iron knee crank to a steel socket, to make a redneck power feed for the knee of my mill. After doing some research, decided to use aluminum-bronze filler and AC TIG. Had to fiddle around with the amperage a bit, and it brazeded rather nicely. Looks to have penetrated/flowed fairly well. Preheated the parts to 400F, and had the welder set at 120 Hz AC and cleaning action at 90%, with Argon at 15-20 SCFH. 3/32” tungsten and #8 cup w/gas lens. Started out at 40A, which was way too cold, as was 50A. At 60A, it was starting to puddle and flow, but it took longer than it should. 70A turned out to be just about right. Formed a puddle quickly, but if I lingered a bit too long, it would start to melt the base metal ever so slightly. Then dressed it down because A.) it looked terrible! and B.) I wanted to check for porosity and wetting action. We’ll see how it holds up. The drill motor drives the knee pretty well without feeling like it’s working it too hard.
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Nice work Jeff!  I don't think I have gotten such a nice looking bead with the Aluminum Bronze.  did you notice how easy it "sticks" to the cast iron due to the cleaning action of the AC?  It isn't as obvious as the cleaning of aluminum but you can see the grain structure change and for me it even seemed to melt in some of the cast iron.  Proof is in the pudding and you repair will be permanent. iMO it would have been beneficial to "V" that joint out a bit more since the over bead is ground off.  The aluminum bronze is surprisingly strong and tough stuff.  

it is fun watching your new machine come together, thanks for sharing!


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## akjeff (Nov 19, 2020)

NC Rick said:


> Nice work Jeff!  I don't think I have gotten such a nice looking bead with the Aluminum Bronze.  did you notice how easy it "sticks" to the cast iron due to the cleaning action of the AC?  It isn't as obvious as the cleaning of aluminum but you can see the grain structure change and for me it even seemed to melt in some of the cast iron.  Proof is in the pudding and you repair will be permanent. iMO it would have been beneficial to "V" that joint out a bit more since the over bead is ground off.  The aluminum bronze is surprisingly strong and tough stuff.
> 
> it is fun watching your new machine come together, thanks for sharing!



Thanks Rick. Agree, the V should have been much deeper. I also need to move faster, or back off a few amps to reduce/eliminate that swirling in the edges of the joint. The base metal was melting a little and mingling in the braze. The AC worked great. As you noted, the cleaning action was definitely visible, and did it's job well. Since this will be a pretty low stress part, it should hold up fine, thin joint and all. Sure will save some cranking!


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## NC Rick (Nov 19, 2020)

I am not sure the small amount of metal intermingled is bad.  Maybe but the first thing I used it on was a cast iron bed from the turn of the last century.  It had broken right in the most stressed part where the longitudinal member connected to the headboard.  The cast component hung from pins on the headboard and in the ninety degree corner of the casting, snapped "right half in two"   I repaired it in the same way you have done your knee drive and it has served it's owner well.  Perhaps the real test will come many years from now when it gets used enthusiastically by a pair of newlyweds.  I will likely never know.  I'll tell you that the size of the beautiful casting was pretty small.


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## GunsOfNavarone (Nov 19, 2020)

I love silicon bronze but have never used the aluminum bronze. I recently brazed a chromed socket to a chromed hammer (for mill) It's amazing how handy it is for similar metals, played metal and such. Welding.....super glue for men!


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## NC Rick (Nov 19, 2020)

Jeff, BTW, how's the adapter work?  I have a mating stub end but it is some time of cast aluminum and the geometry of making my own is a bit intimidating.  All the more reason for giving it a "go" a suppose.  I just wonder how well it will work.


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## NC Rick (Nov 19, 2020)

GunsOfNavarone said:


> I love silicon bronze but have never used the aluminum bronze. I recently brazed a chromed socket to a chromed hammer (for mill) It's amazing how handy it is for similar metals, played metal and such. Welding.....super glue for men!


Silicon bronze is way cheaper and the go to stuff for GP use I think.  The aluminum bronze on cast iron thing came from Jody @ welding tips and tricks and seems really excellent.  I also picked up some 99% nickel Tig filler, just in case.  Without a bunch of cast iron repair experience,  how is a body to know?


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## pontiac428 (Nov 19, 2020)

This is a good application for Castweld 99.  It's a machinable high nickel alloy for cobbling stuff like this together.  It's a stick electrode, but you apply it with TIG.


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## akjeff (Nov 19, 2020)

NC Rick said:


> Jeff, BTW, how's the adapter work?  I have a mating stub end but it is some time of cast aluminum and the geometry of making my own is a bit intimidating.  All the more reason for giving it a "go" a suppose.  I just wonder how well it will work.



The adapter works great Rick! I set the drill motor( an 18V Milwaukee ) on low speed, and it runs the knee really well, and doesn't feel like it's laboring. Can hold the drill with one hand while running it. Sure beats .100" per hand crank!


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