Have you ever noticed that:

When you nail a point, it’s the same as when you hit the nail on the head? Both imply precision, even though nailing a picture to the wall is much different than squarely hitting a nail once. Congrats on not hitting your thumb, I guess.

Then you can hammer something. If you nail a question, you got it right without difficulty. If you hammer your point home, you engaged in rhetorical brutality, pushing your position over and over until you succeeded. But how often do you use a hammer without a nail? Shouldn’t their respective metaphors be the same?

If a baseball player nailed the ball, the phrase implies he swung the bat accurately and skillfully. If he hammered the ball, he struck it with a powerful swing.

It goes to show how two tools that work together for a single purpose (to attach one thing to another thing) can take on different connotations. Once that divide occurs, the metaphors begin to diverge even further. After all, what would you think if someone said, “Man, I got so nailed last night, and then I hammered this chick?”