The 120V AC wired Harbor Freight 1/4 Die Grinder has a flaw in that the plastic will crack near where the four mounting screws get their internal threaded purchase.

If you line up a drill bit correctly and hold it steady, drilling on through the plastic to the metal frame beneath and using a longer screw or all thread as a stud will strengthen the assembly enough to prevent the cracking.

Sugru moldable epoxy might possibly be used to strengthen the plastic in the weak section.

The formerly $100 Craftsman 1/4 die grinder is discontinued but is a worthwhile purchase at a yard sale if the price is low.