Aleric Rubber End Caps - 60pcs Flexible Screw Thread Protector Covers Rubber Bolt Covers Caps for Metal Tube Rod in 6 Sizes 2mm,3mm,6.5mm,8mm,10mm,12mm

You can get a very decent 12v grinder at Walmart, and there are also screw-thread protectors that could do the job (maybe look for orange ones for safety).