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Old 03-04-09, 01:43 PM   #1
jimmitch
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Flux

I've built 6 lugged steel frames over the last two years, and my technique is getting better. Silver flows where I want it, and my brass fillets are starting to look like they're supposed to. But I still spend way too much time removing the flux. Are there any secrets to this? Which fluxes are the best for silver and brass?
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Old 03-04-09, 04:52 PM   #2
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I've built 6 lugged steel frames over the last two years, and my technique is getting better. Silver flows where I want it, and my brass fillets are starting to look like they're supposed to. But I still spend way too much time removing the flux. Are there any secrets to this? Which fluxes are the best for silver and brass?
Are you soaking the flux off? Heat helps.
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Old 03-04-09, 05:16 PM   #3
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I usually put the joint under hot water in a sink for a few minutes - that takes off the "unglazed" stuff, but I'm still usually left with chunks of hard, glassy material that I have to chip, sand or file off.
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Old 03-04-09, 07:36 PM   #4
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that's why people soak the flux. I'm impatient and usually take it off with a file. There are chemicals that will do the job, but that's a fairly involved process.
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Old 03-04-09, 10:12 PM   #5
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I've built 6 lugged steel frames over the last two years, and my technique is getting better. Silver flows where I want it, and my brass fillets are starting to look like they're supposed to. But I still spend way too much time removing the flux. Are there any secrets to this? Which fluxes are the best for silver and brass?
What flux are you using? In my experience, the Gasflux "type B" blue paste flux works better than any other I've tried and is by far the easiest to remove.

You can buy it from Henry James Bicycles if your local welding supply store doesn't carry it.
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Old 03-04-09, 11:23 PM   #6
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I just use silver flux, but from what I hear of brass, the glassy hard stuff is non-water-soluble. So just be sure to ask your supplier for the water soluble stuff, or buy the stuff sold by Henry James, or other bike suppliers since it will all be water soluble. The stuff that requires chipping off can lead to damaged tubes, and is a royal pain. Just in case you are using that stuff on something other than a bike, they make a useful air tool that fires out a hedgehog's worth of spikes for rattling off the flux.

If you have the right flux, then you just need enough water contact. Something like a wheelbarrow, or a tarp supported on a frame so you can get the whole frame wet long enough to fully loosen the flux. Take some of your glassy flux chips or a small part and immerse in warm water for an hour or so and see if the flux softens, if it doesn't you need to change your flux.
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Old 03-05-09, 06:59 PM   #7
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One of the nice things about silver brazing is that you can get flux that soaks right off. I use the stuff Henry James sells. A ten minute bath in hot water is generally enough to get rid of every trace of flux. Cold water takes 30-90 minutes, in my experience. I did once use a file to remove flux. I still haven't gotten that file completely clean.
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Old 03-05-09, 08:57 PM   #8
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Thanks, all. It seems like I should try to get some Gasflux Type B blue stuff and try it out. Does anyone besides Henry James sell it online? I'd order from Henry James but their website is pretty cumbersome.
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Old 03-05-09, 10:59 PM   #9
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You've really just got to call them. You will be well taken care of.
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Old 03-05-09, 11:00 PM   #10
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Thanks, all. It seems like I should try to get some Gasflux Type B blue stuff and try it out. Does anyone besides Henry James sell it online? I'd order from Henry James but their website is pretty cumbersome.
Unless you already have an account with them you'll have to call them to place an order.

If you're using brass you want the type B paste flux.

If you're using silver you want the type U paste flux.

HTH...
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Old 03-06-09, 08:26 AM   #11
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Just want to chime in here to reinforce the need to get all the old flux off the frame, inside and out. Hot water is the key in my experience. Flux is an acid and if you don't get it all off it can attack the paint and even the metal.

On one of my first frames I removed the flux off the outside of the frame using sandblasting - flux remained on the inside. Painted the frame and rode the crap out of it for one season. Started to notice the paint was bubbling up at the lug edges; the acid in the flux was migrating though pin hole voids in the braze joint and attacking the paint and most likely the metal as well. From then on I started to properly soak each joint to make sure the flux is properly removed.
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Old 03-16-09, 12:05 AM   #12
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I've had good results with a product called Handi-flux. I used to use it as when I worked as a jeweler, it is made for the manufacturing of gold and silver jewelry, but I've also achieved very good results when using it on steel.
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