On 29 Sep, 16:29, Tim McNamara wrote:

Chrome plating *can* result in embrittlement but does not necessarily do
so. *Millions of bikes and other load bearing appplications are chromed
without such failures happening.

More likely the cause of embrittlement is what causes it with non-
chromed forks. Overbrazed.

Current common practice is to use oxy-acetylene torch and spelter wire
because it is quicker overall. I suspect the higher temperatures
obtainable with oxy-acet ensure a deeper penetration of the spelter,
alloying with the steel, causing the embrittlement. In skilled
experienced hands, oxy-acet does produce excellent results when there
are no distractions. I would certainly favour a builder which had the
certification of qualification from a technical college in the use of
oxy-acetylene for brazing if I was unable to locate one with historic
recommendation. That (college cetificate) does not necessarily
qualify him to braze cycle forks. And be careful that builders
although say they do the work, leave spotty Nigel to do the
preperation.

Hearth brazed forks heated with natural gas may also suffer with
brass embrittlement due to excessive duration in the flame. Good
preparation is the key. No cutting with abrasive grit, only by file,
plenty of flux in the joint and the use of granular spelter inside the
end of the fork reduce the heat exposure of the steel so keeping the
alloying depth to a minimum at the edge of the crown. I think it be
the filling from the end of the crown rather the end of the fork to be
the killer.

Nigel, may of course used carbarundum instead of the file and scraper
to prepare the forks and crown and if he's applied a paste flux, how
much water?


The reason for the failure seem pretty self-evident in the photo. *Note
how the crack followed the shore line of the socket so perfectly, and
note the relative thicknesses of the metal. *Note also the lack on a
reinforcement tang on the inside of the fork leg.

Overbrazed.


for the future, consider quality cfrp - unless abused, it's pretty
much "fatigue proof".

More clueless advice from "jim beam."

overbrazed.