Hello,

I'm building my 17th frame for a friend and it's the first time I'll use a seat tube with a thickness of less than .9. It'll use a 28.6 OD columbus cromor for 27.2mm seatposts. I'm using brass brazing and a straight gauge .9 top tube.

Anyway, it seems like something went wrong on the tt/st junction. The inside of the tube seems a little lumpy where I brazed, to the point where it interferes with the seatpost. Not sure how that happened, might be too much heat (unlikely) or on cold setting. I build in subassemblies and had to do some realignment.

I haven't tried a 27.2mm seatpost yet as I don't have one on the shop right now, but I've tried a 26.8mm and it catches a bit, not very drastic, but some force needs to be applied for it to move. I can feel the lump with my fingers also.

What should I do? The frame is not ready, only front triangle. I don't have a reamer and buying one was not on my plans right now. The guy I'm building for is my friend so if something goes wrong it's no big deal, but he wanted to use a carbon seatpost and I'm pretty sure the way the frame is now that'll be impossible.

Still amazed by how a thin walled tube needs care unlike the heavier stuff I was using.

Thanks.