In my quest to find an inexpensive down cut spiral bit in my CNC, I tried a 0.125" Roto Zip bit. Things looked promising for about 3 minutes then the bit broke running at 18K @ 60 ipm. OK, so I need to fiddle with speeds and feeds right? Not! Upon inspection, I discovered that the bit flexes a tremendous amount. The photos show a thru hole centered in a hex pocket except for the fact that the hole isn't round (yes, it was drawn as a circle). The profile cutout shot clearly shows significant flex during ramped plunges. Lesson learned and added to my wall of shame.