Originally Posted by Kai Ju
Not so sure about that. I would think that an over torqued countersunk screw could cause a crack easier than a flat bolt head.
I realize that I'm comparing apples to oranges ( plastic vs. steel ) but I saw so many leaking neutral switch plates on RDs due to cracks from over torqued C/S screws. The key was loctite and just snug the screw enough to seat the cover and compress the O-ring. Let the loctite take care of the bolt retention.
The counterbore for the bolt head is what caused the problem. The bottom of the counterbore is ever so close to the o-ring groove on the other side. Perhaps my cover was somehow over machined bringing it too close to the o-ring groove.
Mind you, this cover was at least 25 years old and had only been taken off once. Possibly over torqued.