Framebuilders - Low rider Braze-on question/ first time brazing

I recently picked up a Schwinn Passage frame off CL. It's a touring frame with most of the expected braze-ons. So that's great, but one of the rear rack braze-ons was busted off, and the fork doesn't have any low-rider mounts. I've decided to do the work myself with the assistance of my boss who has some brazing experience.

First off- the lowrider mounts.

I visited the shop of Matt Assenmacher, by recommendation of my boss, in Swartz Creek, Michigan hoping to pick up some braze bits. He's a frame builder who has built bikes that have won national championships. Here's a blurb about him and some of his frames.

http://www.classicrendezvous.com/USA/Assenmacher.htm

It was quite the experience seeing some of the tubing, nervex lugs, cinelli fork crowns, and such when they weren't built into a frame.

Anyway, I picked up some through lowrider braze-ons, a hourglass rear rack braze on, and a NOS Blackburn Custom Lowrider Rack.

The through low-rider braze ons look like this:

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and here's an image for installation:

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My question for you all is this when I get everything drilled and the braze-on in place, how do I go about brazing it without getting brass on the threads? It appears that the lip goes on the outside of the fork blade, do I braze both sides? How?

Rear rack braze- this was semi successful. Due to my lack of experience, I clamped the rack boss to tightly. When the heat was applied, the combination of pressure and head smushed it and ovalized the hole; enough that a bolt wont thread through. If I can tap this out, all will be well.

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Thanks,
Blake

My question for you all is this when I get everything drilled and the braze-on in place, how do I go about brazing it without getting brass on the threads?
Don't worry about getting brass in the threads; just chase it out with a tap afterward. But AFAIK, the low-rider mounts for the fork blades are not threaded.


It appears that the lip goes on the outside of the fork blade, do I braze both sides? How?
Brass will migrate to the inside of the blade, if that's what you're worried about. But you do want to braze it both where it enters and exits the blade.


Rear rack braze- this was semi successful. Due to my lack of experience, I clamped the rack boss to tightly. When the heat was applied, the combination of pressure and head smushed it and ovalized the hole; enough that a bolt wont thread through. If I can tap this out, all will be well.
Or just heat it up and knock it off, and replace it with a good one. You don't need much pressure at all, just enough to keep it from wandering around as the water boils out of the flux and the flux liquefies.

Don't worry about getting brass in the threads; just chase it out with a tap afterward. But AFAIK, the low-rider mounts for the fork blades are not threaded.

You're right, I don't know why I said that.

Thanks a ton for the tips. I'm finding it very difficult to manipulate the brass, it has a mind of its own.

brazing filler goes to the heat. It will also try to flow to reduce any surface discontinuities. Finally, and almost least importantly, it will go with gravity. None will get on the threads unless you put it there or have a big blob that you push over the edge.


It looks to me like you could have flowed the braze a little better around the stay side. This also leads me to wonder if you got any brazing material between the stay and the fitting. The joint has both too much and too little brazing material.


You can't crush a braze on if you don't overheat it. I would worry more about crushing the stay.