...looks like an aluminum alloy of some sort. I would go with blue Loctite, rather than tightening it a whole lot. Aluminum needs something to cut down on galvanic corrosion as well, or it's hard to remove it somewhere down the line. I don't actually recognize what sort of BB that is ? If it has sealed bearings, the races are in the sealed units, so that cuts down on precession forces on the cup.