Loose Screws in Railings For Stairs

[MrSpeed]

The railing for my stairs are secured by metal screws that go through the stairs and into the railings. The screws always seem to enlarge the holes and then I need to get larger screws and evenyually they loosen up as well.

Is there a better method for securing railings ? I would love to tap the railing and use machine screws but the metal is not thick enough.

Thanks