Bike Forums

Bike Forums (
-   Framebuilders (
-   -   Brazing capped seat stay to lug (

TiHabanero 08-09-18 06:32 PM

Brazing capped seat stay to lug
I am capping the seat stays with scrap pieces of tubing so that the caps are silver brazed to the angled cut on the stays. When I attach to the seat lug will the silver holding the caps to the end of the stays run and ruin the attachment to the tube?

Live Wire 08-09-18 07:26 PM

Yes, it will melt the silver holding the cap. If your heat control is good, it will only melt near the tip and you'll probably be able to touch it up while everything is still hot.
Be a lot easier to use brass, or nickel silver if the caps are stainless.

TiHabanero 08-09-18 08:06 PM

Thank you for the info. Is it OK to use brass on the caps or will it require too much heat? They are simply cromo scraps.

unterhausen 08-09-18 09:25 PM

brass will be fine. Practice on scraps first if you are unsure.

I have spent days on end brazing caps to stays at Trek. Somebody had to do it. Back then, we only used nickel silver on everything that we didn't use silver on. I have always been curious why. Brass would be a lot better, some people develop a sensitivity to nickel silver. Nowadays I only use nickel silver when I'm working with stainless.

8aaron8 08-10-18 07:04 AM

If you are using non stainless steel then brass is the way to go for sure. If the caps or stays are stainless you can also use a lower percentage silver rod such as 35% or 45% because the melting temperature is higher than what you will use to join the seat stays to the seat lug assuming you use 50% or 56% on that joint.

Andrew R Stewart 08-10-18 02:34 PM

For lugged frames I'll brass both the lug and the caps. I, too, make my own from tube shorts or plate and will use silver (56%) to attach the stays to the lug sides. I've melted out silver from a lug, while using brass to attach the stays. Andy.

TiHabanero 08-10-18 07:24 PM

Andy, I never considered the affect of heat on the lug. Suppose it is possible to lose the filler from the lug joint. Welding supply store is closed and the only brass is an 1/8 rod. Too thick for the caps I think. May wait for Tuesday to get the correct rod. I will use brass on the cap and silver at the lug so that I reduce the chance of bleeding out the filler from the lug/seat tube joint.

unterhausen 08-11-18 09:19 AM

I use silver in the lug and brass to attach seat stays. Every Trek built up to the point where they switched to brass lug brazing was built that way. There is some possibility of flowing silver back out of the lug. Flow it back in, it's not going to hurt anything. My expectation is that you might pull silver into the lug and have a gap on your shoreline. If that happens, fill it with more silver.

fietsbob 08-11-18 10:42 AM

In Art metalworking, we use several different melting point silver solders,
going from high to low, Aka 'hard to easy'

so sub-assemblies don't come apart while you are attaching them..

I used a single wrapover piece , on the (Aelle) frame I built , Brass brazed, in the mid 70's..

Silver is needed for stainless steel lugs you using those?

JohnDThompson 08-12-18 04:06 PM

If you're going to use silver to attach the stays to the lug, it's a good idea to file a little trough into the side of the lug for the stay to seat into. This will give a larger surface area for the joint. Plus, it looks pretty nice.

unterhausen 08-12-18 08:26 PM

John, I have never done that, I am going to try it on my next frame

Andrew R Stewart 08-12-18 09:33 PM

Another cool thing about filing a shallow trough in the lug's side for the stay is that the stay tends to not slip about during brazing. Not a problem if you've jigged the stays well to the frame. But many here don't know the tricks of have much tooling yet developed. Very good tip, John. Andy

TiHabanero 08-14-18 09:02 PM

Picked up a brass rod at the local hardware store on Saturday. Fortunately we still have a couple of real hardware stores left around here. Made a practice cut and then was promptly interrupted! Will be playing some more with it in a day or two and will let you all know the results. The file a trough into the seat lug is a good idea.

Andrew R Stewart 08-14-18 10:05 PM

TiH- I would strongly suggest you try the GasFlux C04 bronze rod available from Henry James, and others. Their type B flux is a standard for many builders too. Andy

unterhausen 08-15-18 05:50 AM

the bronze I bought from my local welding shop doesn't flow very well. I can make it work, but the Gasflux or Cycles design bronze is much better

All times are GMT -6. The time now is 03:10 PM.

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.