Originally Posted by
Zinger
John are you sure that's a stamping ? I have to agree with SJX426 in that it looks to me like a forging (or maybe green sand casting?) in both what looks to me to be parting lines (on top and inside the triangular cutout) and the texture at the bottom of the dropout around the derailleur hanger where the hand grinder hasn't hacked on it.
Also not a milling finish or uniformity around the radius. Radiuses don't look stitched with a ball end mill either. That would be a mighty expensive way to make a stamped dropout even if it was.
I'm aware that you worked for Trek but are you sure about this one ?
Interesting thread though.
That is the picture I was referring to. The pic in post
#52 is a little more ambiguous-- if forgings they are pretty sleazy looking, yet if stampings, there's been some significant post-processing to create the rounded edges. On close comparison of the two photos however, there is nothing to suggest the dropouts in the two photos are actually different; only that one set has been brazed into a frame, with brazed eyelets added. So now I'm accepting
JohnDThompson's assertion that they are in fact stamped, abeit with significant post stamping prep to make them look "nice". Either that, or a quasi-forging process, where the stamping die is not merely a cookie cutter, but has a female contour that creates the rounded edges that are so evident in the photos.