On 09/29/2009 03:15 PM, Jobst Brandt wrote:
Jay Drew wrote:

What is feathering?

A fading out of one cross section into another where they meet:

http://www.gtgtandems.com/tech/brazing.html

wrong. feathering is simply filing the edges of the lug.



The sudden step in cross section causes a stress concentration that
leads to cracking.

which is why it's not a straight cross section, it's got curved features
that mitigate - effectively radius reduction, a standard fatigue
mitigation technique.


Most better metal workers are aware of this.
Sadly the sloping fork crown of 1960's Cinellis were not feathered and
cracked for those of us who rode much.

that's not feathering - that's radius reduction.


After two of these failures I
got a Masi Fork crown instead.

good for you. of course, if you'd understood what you were looking at
the first time, you'd only have suffered one failure...



Feathering can be done as Hetchins did with curlicues and fade-outs,
or as Masi did with tapering pointed lugs.

nope, that's radius reduction, not feathering. hetchins and masi [and
many others] do feather, but they do it with a file, and it's not a
function of lug shape.