I have been wondering about the logic behind the shape of needle tips. This all started when I had a go at making my own 0.18mm replacement needle for a Creos PS-771 by turning down a Chinese needle. After a bit of trial and error, I found I had to use a 0.5 mm needle as the starting point. The Chinese 0.2 and 0.3 needles projected way too far out of the nozzle. When I examined the Creos needle I was trying to replicate it was relatively blunt and had a two-part taper with a change of angle at the tip. This seemed counter intuitive, but clearly it works for current Microns as well. I remember my old Holbeins had needles with a very long graceful taper and mentally associate that with fine detail work. I came across a YouTube video of some guy having a rant about the blunt Iwata needle not working on his Olympos micron airbrush which kind of got me wondering about when the design philosophy changed and why.