In a post today, Wild Bill sez:
"From the diameter and length you gave Michael, it looks like they are officially referred to as non-standard Chinese (at least by this source in the UK).
Any time someone posts a collet chart or comparison guide (or machine spindle tapers), I try to remember to save a shortcut to it/them and put them in a metalworking collet info folder. I had more of them on my last machine, but here are the ones I have presently" Then he listed several relevant URLs.
Visit the UK site to glean a ton of valuable information on collets and just about any other category in the mechanical arts.
One thing I found particularly noteworthy was an essay from the esteemed English Engineer John Stevenson, "Reasons to convert a mill to CNC". It can be found at:
Although I am not presently a candidate for "conversion to CNC", I found John's article to be an insightful and provocative intro into why someone might want to go CNC.