Eye protection, and if there is sanding involved respritory protection.
There have been any number of times when I have been merrily cutting on metal and sparks are flying everwhere, and the occasional "CRACK!" when a piece shoots off and hits the lens' of my goggles. And, grinding down metals will produce fine airborne particles that are best kept out of the lungs.
I look goofy, but I can still look...
Every case modder needs an idea and some ingenuity.