Originally Posted by
Dave Kirk
Cool.
My experience with shells is that they are faced very well from the casting house and are fine without facing to start but it's after they have been heated asymmetrically (all the tubes being on one side) that the top side shrinks and the faces go wonky.
Have you measured the width/parallelness of the shell after brazing? I would expect that you would find that the top side (where most of the heat is) would get narrow. I usually see the top being about .005" narrower that the bottom and when projecting this angle over the length of the seat tube you end up with the top of the seat tube being low which would result in the top of the seat tube being about 2 mm low on the plate. This is one reason I face post brazing. The other is that I want the faces that the BB bearings snug up to to be parallel so that the bearings will have the easiest life possible.
dave
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