Braze-ons BEFORE Mitering?

[Ahmdo Molah]

I recall Mr. Don Ferris once mentioned*,
*bottom of post #92 , p.5 of Anvil Bikes' Smoked Out.
https://www.velocipedesalon.com/foru...009#post250009

"I make it a point to install any braze-ons BEFORE I miter the tubes if possible and certainly before I install the affected tube in the fixture. Braze-ons will distort the tubing and it can make your life miserable doing it after the frame is built because it can affect your alignment."

This makes a lot of sense. Removal of any stubborn flux or rust from soaking would be a lot easier too, as a more "direct" visual check would be possible, without say an endoscope(!). And any distortion in the tube would affect miters that were done prior to brazing (throwing off alignment).

But (if I'm not mistaken) it seems many builders just add braze-ons at the very end, after the frame is mostly welded(or brazed) together,

Why? Is the affect on alignment so small it is negligible?

Do any of you do braze-ons BEFORE mitering(?), and if you do, can you share any insights regarding;

1. How you straighten tubes if any are slightly affected after braze-ons
2. How you hold(secure) the tubes for mitering, if a braze-on say a cable stop is near the miter point

Pictures of your solutions would be great! Thanks~

[Andrew R Stewart]

That so many frames have their braze ons applied after the tubes are joined and that these frames work well enough for riders to not know any difference suggests, to me, that any alignment distortion is so small as to be a non issue.

1- I don't straighten tubes after braze ons are applied. I do make sure the frame is aligned to whatever my standards are.
2- The tube might be held in a different location if a braze on were to otherwise interfere with your tube clamp during mitering. How one clamps the tube might need to change. But this would be part of figuring this braze on before mitering thing out. Andy

[false_aesthetic]

I can't remember the exact build number but it was between #2 and #5 I added the braze-ons before I welded the frame together.

At some point I rotated the frame in the stand for better welding access and completely forgot about the braze ons. I ended up denting the frame. That, along with some other early mistakes, lead me to attaching any sort've "nubbin" toward the end of the build.

[Ahmdo Molah]

... At some point I rotated the frame in the stand ... and completely forgot about the braze ons.

SCREAM.jpg

Thanks for the heads up, or SCREAM in advance!

[Rich Beaudoin]

The general rule I use: if thing’s needs to go into it the tube wall, I braze them before welding the frame (bottle mounts, internal routing, etc). If the piece simply gets brazed onto the tube, I braze them after welding the frame (cable stops/guides, rack mounts, etc).
I don’t notice any affect on frame alignment, but I get much more accurate results with the placement of braze-on mounts when I can eyeball the whole frame.

[Curt Goodrich]

I like to braze on the front derailleur mount after the frame is built. But heating off the center line of the frame can effect the alignment. To counteract this, I flux the entire circumfrence of the seat tube at the mount. Immediately after brazing the mount on, I heat the fluxed seat tube 180° from the mount. A soft gentle flame heating until the flux goes glassy. This greatly reduces the heat warpage. I use the same technique on chain stay bridges. That's just how I do it. Ask 10 framebuilders about this subject and you'll get 11 opinions.