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Old 02-09-10, 09:14 AM   #1
theschwinnman
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modifying bike frame

I have a vintage steel bike that I really like, it rides really good, and is pretty lite. It does however have a few deficiencies, it has no bottle cage braze-ons, no shifter boss braze-on, and weird cable routing (it uses a clamp on cable guide that was designed for a FD with a built in cable housing stop, so one side is just a cable housing end).

I'd like to braze on some shifter bosses Like these, water bottle cage bosses Like these, and a new cable housing stop Like thisto the underside of the chainstay, so I can use a under the BBB cable routing system.

I'd like to use silver brazing material, since it melts at a lower temperature than brass, however, I am unsure if it work...

Also, I have two torches at my disposal, one is a butane micro-torch, and supposedly burns ar 3000 degrees, the other is a full sized pluming torch, and supposedly burns at 2500 degrees. Would either of these torches be suitable? Also, where might I get this silver brazing material?

Thanks for your time.
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Old 02-09-10, 09:59 AM   #2
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I have a vintage steel bike that I really like, it rides really good, and is pretty lite. It does however have a few deficiencies, it has no bottle cage braze-ons, no shifter boss braze-on, and weird cable routing (it uses a clamp on cable guide that was designed for a FD with a built in cable housing stop, so one side is just a cable housing end).

I'd like to braze on some shifter bosses Like these, water bottle cage bosses Like these, and a new cable housing stop Like thisto the underside of the chainstay, so I can use a under the BBB cable routing system.

I'd like to use silver brazing material, since it melts at a lower temperature than brass, however, I am unsure if it work...

Also, I have two torches at my disposal, one is a butane micro-torch, and supposedly burns ar 3000 degrees, the other is a full sized pluming torch, and supposedly burns at 2500 degrees. Would either of these torches be suitable? Also, where might I get this silver brazing material?

Thanks for your time.

Either torch should be fine with silver.
Use either AWS BAg5 (45% silver) or AWS BAg7 (56%).
BAg7 works at a lower temp range of 1200 to 1400 F.

Use an AWS type 3 flux (paste form is best for braze-ons).

You can get the materials at any welding supply.
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Old 02-09-10, 11:42 AM   #3
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or you can order everything from Henry James. Before you do this modification, you might want to consider leaving the bike in its vintage state. It's pretty easy to get a better bottom bracket cable guide on Ebay. Somehow we lived with clamp on cable guides and water bottle cages until the late '70s. In fact, my current main ride has a clamp on water bottle cage on the seat tube.
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Old 02-09-10, 01:29 PM   #4
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I really don't care if the bike is original, I'm replacing all the components on the frame with new nine speed stuff, and since it's going in for a powder coat, I thought I might as well modernize it. Thanks for the information, casscave. Is their any guide on the internet for doing this, I have soldered copper pipe, but I'm certain that this will be different.
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Old 02-09-10, 03:18 PM   #5
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I really don't care if the bike is original, I'm replacing all the components on the frame with new nine speed stuff, and since it's going in for a powder coat, I thought I might as well modernize it. Thanks for the information, casscave. Is their any guide on the internet for doing this, I have soldered copper pipe, but I'm certain that this will be different.
It's a lot different from copper pipe.
Your flame will be much lower (copper conducts heat at 6.5 times the rate of steel).
Use a soft, slightly carburizing flame and PRACTICE on some scrap. Braze a few nails or something to a piece of thin wall steel tubing or even some 20 ga. cold rolled sheet.
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Old 02-09-10, 03:29 PM   #6
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It isn't entirely different from copper, same principles apply: heat control is paramount, clean welll flux thoroughly, heat where you want the solder to flow to, be careful about not adding the solder from so many places that you encircle a dry spot, etc... But as said it is also different. It's like walking uphill, same basic principle for climbing mount Everest, but it is going to take a while longer to acclimatize to Everest.

Water bottle mounts are about the easiest to braze there is, you make you hole, peel back you paint, fit, clean, flux, and point and shoot, periodically touch the base with the wire, and all of a sudden it will suck in and self level, play flame to draw around. If the insert seems unstable before you start, you can balance a heavy metal thing on it, or from something adjacent to it, to hold it in place. Do not flux inside the part or to the hold down, or you will end up with a lot of solder where you don't want it. you can also wire it down, though I tend to end up with stuff attached to the frame when I do that.

Last edited by NoReg; 02-09-10 at 03:34 PM.
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Old 02-10-10, 01:29 AM   #7
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i agree with most above. Dont waste your time with ordering flux or silver if your supplier doesnt have them (one of the reasons i order true temper for HJ is i can get great consumables *hint for nova*), and 45% will have plenty of strength for these apps, and the gap filling may just come in handy for you as a beginner. Bottle bosses are easy, but after i gave the tinning a try, for guides and such, i wont go back. for this you tin (a little peak of about 1/32nd thick of filler is nice here), then tin your boss, clamped in some needle nose. reflux if you feel like it, place it where its gotta go, heat up, and watch the marriage occur with a steady hand for about 5 seconds after the melt and flame has been removed. Ive pissed around with boss clamps far too much, and for many apps this is a great tech. Personally i think practicing with silver for boss' is a waste. If the metal gets orange with a micro torch and you havent had a good flow occur, you have filler or cleaning problems, no biggie, clean again (sanding is one of the best cleaning agents out there, make sure it is sanded nice and bare first, and then if you like, acetone is nice with silver i find, or some snobol, and go at it. using a 2500f flame on silver will give you a huge window...keep the flame dancing around at all costs still. The hardest part here is getting those bottle boss' center on the tube, 1/16th of an in never looks so drastic as it does on them. anyways, im done rambling. have fun.
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Old 02-10-10, 01:24 PM   #8
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Tinning, intriguing... would this work for the shifter bosses and cable stop as well?
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Old 02-10-10, 09:48 PM   #9
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Also, where would I go about getting the brazing rods and flux?
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Old 02-11-10, 12:59 AM   #10
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Also, where would I go about getting the brazing rods and flux?
I buy 45% and 56% cadmium free silver brazing alloy and flux at a local Praxair, but any welding/brazing supply house should have them. 3 ounces of silver is $100, and a pound of flux is $15 - $20.



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Old 02-11-10, 01:32 PM   #11
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yup tinning will work with shifter bosses by all means. Although these bigger braze ons with butane may take a while to get to temp, and your arm holding it in place may get a bit tired. What i want to stress mostly about tinning is that fact one is certain that both frame and boss have complete surface adhesion of the filler. That said, there is one Achilles heel to it, and that is after the melting temp has been reached, and one is letting it setup, any movement can be catastrophic to the bonding strength, and often without knowing. get comfortable when heating it up, and hold steady for atleast 4 or 5 seconds after removal of heat.
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Old 02-11-10, 02:06 PM   #12
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Thanks for all the help, you guys rock.

I think I'm going to just use silver brazing, it looks a tad easier than tinning.

Would this brazing alloy work http://cgi.ebay.com/Silver-Brazing-A...ht_1220wt_1166?

I don't relish the Idea of spending a lot of money, since I'm going to do so little brazing...

I found the flux online for pretty cheap though.

Again, thanks for all the help.

Last edited by theschwinnman; 02-11-10 at 02:12 PM.
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Old 02-11-10, 02:55 PM   #13
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jon,

tinning is brazing. it is just a method. and there is no need to order stupid quantities. I dont know where you are at, but around here you can pic up bandsaw blade repair kits, that often come with 1oz 45% silver, and about 4 ounces of flux for under 20 bucks, and it will do you just fine. Get cad free if you can, doing a few braze ons isn't a big deal as it accumulative, but nonetheless is no good for anything with a central nervous system.
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