Several Presidential administrations ago when I was an 18 year old in Southeast London working at Witcomb Lightweight Cycles, one of the first hands-on tasks I was shown, and allowed to do, was lug preparation for the staff framebuiders. Profiling a lug was the term used to describe taking an as-delivered part and squaring up the edges using a 6″ half-round file. The desired result was that the wall would then be 90 degrees to the pipe and allow for a crisp shoulder. Lugs came in many lengths, shapes, and designs. And all of them needed a maker’s hand to improve their lot in life.
For so many years, I continued on with what I was shown. Then in the early 1980s, a switch was flicked in what would later become the RS Mind Palace. If making the edge a pure right angle to the pipe was the goal, it left little to no margin of error for the consistency of the filler material used in the joining process. Complete penetration of a lapped joint is always paramount, but one wants the work to also look good. Sloppy or heavy brazing, cleaned up using any means, is dirt floor and taboo. By then, I’d been at the bench for a decade and still never used or owned rifflers or needle files.
It occurred to me that 90 degrees was the wrong number. From that point forward I began beveling the lug edges inboard by maybe half of the right angle. The complete shoreline is cut so that the lug edge veers inward. Careful brazing is one’s best safety net against bad joints well as a bad looking one. But according to my opinion, angled-in walls assist in keeping filler material buildup to a minimum.
All This By Hand