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Old 03-09-12, 06:12 PM   #1
Andycapp
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Flux?

So, I've got my tubing, lugs, and all the other bits and bobs. I also got some strait gauge 4130 from Spruce to practice with. I'll be shopping for my torch handle/tip this weekend. Question: The guy at the weld shop I was in earlier recommended a powder type flux called Marvel- "just dip the rod in there, works great!". Everything I'm reading/seeing shows you guys using a paste type (Harris?) and slathering it on pretty generously. Has anyone used this powder type? Results? Thumbs up or down?

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Old 03-09-12, 06:39 PM   #2
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I have used the powder type flux, and it's a pain to deal with. I used to use it for bridges and dropouts. You can actually turn it into a paste by pouring boiling water on it. At least he didn't try to sell you silver flux

I think the powdered fluxes are not all that great for you, I would go with Cycle Design
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Old 03-09-12, 06:43 PM   #3
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I've always used paste flux. It's true, the powder stuff is really a pain and it does not work very well in reducing oxidation and increasing flow like a paste does, in my own experience.
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Old 03-09-12, 06:46 PM   #4
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While brass/bronze is more forgiving of poor prep, cleaning and lack of flux and many just want to get the job done as fast as possible, these are no reasons to not follow best procedures. So most here will suggest that you prep well. Clean by sanding fully down to bright surfaces. Have your fit up as it needs to be, not almost right. And use flux on all brazing surfaces before starting to heat up. Powder won't stick to steel unless the metal is hot, and then the oxidation that flux helps prevent has already started. paste will stay put while heating up and by the time the water steams off the resulting powder will stick and do it's job. Which flux can be debated but many find the GasFlux company type B the best for brazing and clean up. I'll dip my warmed up rods directly into the paste as i feel the need to have more flux on the joint. I do have generic powdered flux and might sprinkle some on (just a pinch will do you) fillets if the flux is getting "old". As you get more proficient you'll find aspects that you can short cut but when starting do the full thing. Andy.
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Old 03-09-12, 08:55 PM   #5
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I use the Gasflux paste too, it's really great.

I've used generic powder a little bit too, but I thought it generated more glare under the flame, and didn't soak out very well in warm water. That being said, I don't see why the powder wouldn't work. It's the same as the paste basically, they are active in absorbing oxides at the same temp. range, i.e when it's already hot. I've seen some videos of Zullo and Pegoretti where they heat up the joint, then dunk it in a box of powder. Doesn't look like they use paste? Presumably the flux will flow before the filler to clean the metal ahead if you're sweating a socket... Gotta give it a shot one of these days.
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Old 03-09-12, 09:01 PM   #6
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I haven't been able to make powdered flux work for me. Harris flux is much more straightforward IMO.
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Old 03-09-12, 11:37 PM   #7
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That's what I was expecting. Thanks guys.
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Old 03-10-12, 11:10 AM   #8
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I forgot to mention that the powdered flux is apparently made of powdered diamonds, because when you try to take it off again you will have to use carbide tools to chip it. You can't even buy it around here anymore though
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