Originally Posted by Andrew R Stewart

bikingman- I would advise against the seat stay attachment design you mention if you are using a lug. Why? Because the lug won't extend down to where the stays butt into the ST and you'll have only the ST wall to handle the compressive loads stays place on the ST. If you go with a single butted ST then that will be a .6 (commonly) wall, not what a novice should be brazing a stay to. If you use an externally butted tube the what lug will slide over that tube end? You could extend the lug's "skirt" on the ST back side down from the lug to provide the platform for the stays to attach to, like the classy Raleigh Pros from the mid 1970s did.

Why the need to have the stays attach so far down the ST? In some miss belief that the rear end will be stiffer? Or fashion? Both are wrong or opinion.

Most common lugs have the binder bolt ears already formed so no added heat cycle there. But if you decide to make a sleeve or lug then braze the binder barrel on before doing the ST/TT joint to avoid having more heat cycles that involve the tubes. Your want of a lug and a separate binder collar is not the norm as lug ODs and binder collar ID's are not thought of being made to fit each other. Do your homework here well before continuing.

I'll end for now with the use of a double butted ST where the top butt in internal (what is usually had when a TT or DT is used for the ST). No big deal. But you will be reaming a lot off the ID if you want a 27.2 post to fit. Not wrong and the thicker wall at the joint is what newbies really should seek out. Just a lot of after brazing work with a reamer. Andy