Maybe you might grind on it. I didn't say that. Milling is a lot different than grinding. You can get an end mill that will fit in a regular drill press or even a hand held drill for under 5 bucks from harbor freight. I dismiss what the factory did there if they omitted a washer. Between a steel bolt and soft aluminum, there should be a washer, IMO. I ain't the sharpest knife in the drawer, but I ain't the dullest one either. I would put a washer there some kinda how.