Originally Posted by bertinjim

Any metal frame will have a non-round seat tube. The welding or brazing leads to an out of round condition due to heat distortion and typical manufacturing does not address this. Every metal framed bike should have the seat lug opening reamed, de-burred, radiused and honed. That will prevent marring or stress riser notching of the post and will allow for uniform and the minimum clamping force necessary on the post.