Brazing a fork - first time

[bouldergary]

brazing a 650b fork with fork blades that fit tight in crown as well as drop outs, 56% Silver will be fine there. I am curious about the steer tube to crown. Fits tight as well, I have seen this done with both 56% silver and bronze brazing. I have done enough brazing of Braze-ons to frames that i feel ready to jump to a fork.

Will 56% silver braze be ok if done properly?



I think i have searched forum well to make sure this has not been covered.

Ty

I found a good post on another forum

Make sure the steerer to crown fit is easy, meaning the crown will slide along the steerer when pushed lightly with very little pressure.
This is important, because even if you get all to correct flow temp the braze will need clearance to flow.
Most steerer to crown failures are from the steerer being tight in the crown, and the braze flowed along the edge and maybe even found it's way to the bottom of the crown along a small path, but not all the way around the joint.
Thus fooling the builder into thinking the joint is correct. {seeing braze at both ends of the crown
Many times in the factory the chap brazing was not doing the fit up of the parts.
Make sure your fit ups are correct
Clean mechanically the inside of the crown and the outside of the steerer
I pin the crown to the steerer to ensure it does not move when brazing
then flux and braze within minutes
Use a big flame, not small hot intense flames {common mistake I see is the small hot fast flame}
I use a five jet small rose bud for the crown {and LPG/Oxy torch}
Feed from one end and witness it coming out the other end
I feed from the crown race seat and flow to the bottom of the crown, the excess is filed/cleaned off from the underside of the crown.
Some builders flow from the bottom to the crown race {with the crown steerer assembly upside down }
this is cool.

Fork blades is the same, make sure they are not too tight!


Good Info Dazza ty

[charliedid]

I'm sure a few people here can answer your question but if you have not already post it here as well.

https://www.velocipedesalon.com/forum/f10/

[jemdet]

My "n" is like 10 here, but I never liked silver brazing steerers to crowns. Easiest when the steerer penetrates through the crown, I went from bottom of crown to top because it made for easier finishing.

Both thick pieces of metal, and will take longer to heat up than a typical tube / lug interface. Have to make sure that the steerer inside the crown is hot enough.

Biggest pitfall would be getting brazing material around crown race area and around bottom of crown, but having blind gaps inside. Best approach is to try a few and cut them up.

Oh! And if you're brazing a threadless steerer, be advised that they are directional. Fatter end at the bottom.

[jemdet]

Some more musings:

Work with gravity.

Once your emery cloth clean-up of the steerer outside / crown inside is complete, do a final pass where you striate the surfaces in the direction that you would like the braze to flow.

Be careful about how you secure the fork steerer. Don't clamp it in a rubber repair stand unless the stand is on its way to the curb. I used to clamp a dead fork blade in the stand, then shove that inside the steerer to get heat away from the stand.

Do you have a jig? Some way to check alignment after brazing? A way to rake the blades? A way to make sure that the dropouts are parallel and 90 degrees to the crown before and after brazing? A crown race cutter?

If this is a canti fork - do you have a canti boss jig or the ability to make one? If disc, are you using disc-specific blades?

[bouldergary]

Thank you for advice.

I do have a jig and alignment tools. Sounds like i should go bronze.

[unterhausen]

I'm not sure I have ever used brass for a crown. There is a lot of surface area, no problem with strength. Not that there is much difference in strength between the two fillers anyway. The only thing I have to advise is to only fill from the one side and pull through to the other. I always do crowns first and then blades. For one thing, on most crowns you can see that you have a nice fillet through the sockets.

It takes a lot of heat to get filler to flow through the joint on a crown, so be patient. Don't try to force it. The temptation is always there. It will eventually all get up to a temperature where the filler will flow. Silver flux remains active just about forever if you don't overheat it. You're looking for a pinkish red.

If you use LFB, watch some of the youtubes of people doing the same. It takes a lot of heat to get brass to flow. Does your setup have the heat capacity for that? I'm not sure mine does without overflowing my acetylene bottle. I see no reason to use brass on steerers and this thread certainly hasn't changed my mind. I would get some 1/8" thick 4130 tubes that nest with each other and braze a 1 1/2" length of tube onto the other tube with the process you chose. Unless you feel like wasting steerers and crowns for practice. All the forks I have seen with steerers that weren't properly brazed in were done with brass. But if they had flowed filler from one side to the other, those failures wouldn't happened.