Belt drive kit installed on mini-mill. How to Break Gear Teeth. I ve had my mini-mill for about six years now and it is an indispensable part of my shop. Mine is one of the early Grizzly models Grizzly Green with a gas strut and #3 Morse Taper spindle. Even though I now also have a larger Sieg X3 mill the mini-mill still gets frequent use.