Originally Posted by
Nessism
Are plug inserts into the stays and fork blades the conventional method to achieve the domed ends?
Well it's not weird or anything, but it's definitely not the most common way. Prolly 99% of bikes with domed ends got their domes from the tube maker, e.g. Reynolds. Not an extra insert, it's just the metal of the tube end formed into that domed shape.
You can also "forge" your own domes, but it's a fair bit of work, and most people would say it's not worth it, at least from a commercial standpoint. Even back when custom steel frames were what every bikie wanted, very few customers were aware of such small details, so the extra work you put into making custom domes was mostly for the framebuilder's own appreciation. So with rare exceptions, when you see domes, they came that way from the tube factory.
The ones I made had a longer taper, more like a parabola instead of a semi-circle like a Reynolds dome. I thought they were elegant but customers responded with a yawn, so I stopped doing it. Jim Merz has told just about the same story.
Mark B