I've been using small end mills (down to 0.01" diameter, or 0.254 mm) for many years as part of my hobby making small injection molds. At first I used trial and error, but that was expensive. Here I show some of the things I've learned that allow me to use micro end mills without fear I'll break them (or at least, not as much fear). GWizard is the tool I'm using for this. It's a great tool.