This is the lightest stem we make, and the bore is what limits it. The hole through the centre stays the same whatever the outside diameter, so as the stem is taken thinner the wall left around that bore gets thinner with it. The taper stops where the wall does.
It is turned in one setting rather than being taken off the lathe and returned, because a slim stem that has been re-chucked almost never runs true a second time. Everything from the thick end to the tip is cut in a single run.
Finishing is oil only, worked in and wiped back until the wood stops taking it. No stain, no filler. The single brass ferrule at the tip is the only hard material on the piece.