I have a bike with a 27.2 seat tube that continues to zig zag seat posts. I have made sure that the seat lug is opened enough, de-brurred the seat tube interior with a drill operated, carbide ball hone, sanded the tube interior with 150 grit & 400 grit sand paper, sanded and filed the slot at the t back of the seat lug so there are no sharp edges.

All of this done and I am still getting the dreaded marks when a seat post is greased up and installed. This has lead me to buy an adjustable reamer. I have never used one before and looking for any tips/tricks from the experienced members of the group.