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Removing braze-on fittings

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Removing braze-on fittings

Old 12-01-14, 09:52 AM
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David Newton
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Removing braze-on fittings

I want to remove a brazed-on front derailler mount, the tube is Columbus SL or SLX.
I do not know yet if it is bronze or silver soldered.
Will a mapp-gas torch do it?
What are the preparation steps?
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Old 12-01-14, 10:19 AM
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duanedr
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Here's how I did it with O/A set up. Not sure if MAPP will get hot enough - it might, I just don't have any experience with it.

Clear all of the paint away from the area. Give yourself 2-3 inches in all directions. Assuming you're not repainting the whole frame, wrap wet towels around the tube at the edge of the paint. Get the braze on red hot while keeping the heat away from the tube as much as possible. The tab will get red on the outer edge so, focus the flame on the base of the tab so the heat transfers to the mounted surface. As braze on gets red and the tube under the braze on starts to get slightly red, grab onto it with some long pliers and gently peel it away. you'll likely need to file brass off of the tube for a smooth finish. Take your time.

Another way to remove it, which will do much less damage to the tube and paint, would be to cut it off and file it flat. But that wasn't your question. For this you'll need to be very careful to not remove tube material. Again, take your time and go slowly with a small fine file.
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Old 12-01-14, 10:38 AM
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mrv 
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I've been using MAPP/air to silver braze on a few bits here and there.
I have been unsuccessful using MAPP / air to get brass or bronze to flow. It'll soften a bit. That might / maybe be enough to pull off mount.
Wear your safety glasses and your respirator when you start cooking that paint!
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Old 12-02-14, 12:17 PM
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If it's attached using brass, MAPP/air won't get hot enough. If silver, it may work. Fuel/oxygen definitely works. Duanedr's hints are good; I'd add: if possible, position the frame so the braze-on is below the tube. That way gravity will help it fall off cleanly when the brazing material liquefies. A bucket of water can be placed to catch the hot braze-on when it falls. A quick swipe or two on the seat tube with a wire brush while the stuff is still liquid will reduce your clean-up work afterward.
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Old 12-02-14, 01:06 PM
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Thanks for the good tips.
I'll have to find someone who has a Oxy/Acetylene rig that I can use. There are no frame builders near me.
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