Hi Sven,
I couldn't find any info online, so I went out and measured one. I believe the half angle is exactly 8 degrees (16 degrees included angle across the entire collet). I did this measurement with the rise of the dial guage (.1405" to .141") in 1" of longitudinal travel, so I'm quite certain this would be accurate.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)