Theres this axle thread size slightly thicker than a standard m4 but nowhere as big as a m5. It is used by yyj from solid spin onward, clyw large hub models, and i believe some of 2syy and genyo as well (maybe queen, prophecy, didnt unscrew to check). What is the correct name for it?
The YYJ models with the solid spin axle use an 8-32 thread screw.
It can be found here: Common Yoyo Axle Sizes