Some time ago, my 3 year old princess got a play set that consisted of a thick board, small nails, a wooden hammer, and lots of little wooden shapes with a small hole in the middle. The idea is that you can nail the shapes to the board to make houses, stick figures, etc.

While she was playing, my daughter complained that the nails wouldn't go in all the way.
I gave it a try, and the problem wasn't the board or the nails. It was the fact that the crappy hammers were near weightless. This makes them perfectly safe as toys I guess, but it also makes them pretty useless as hammers.

So I told her that indeed, these were bad hammers. We went to my favorite hardware shop and chose a lightweight carpenters hammer. With that one she had no problem hammering the nails.
I also bought her an ounce of real nails, which she happily hammers into a discarded foot of 2x4.
I may not have a son, but my daughter is eager to learn to use tools, so I am happy to oblige. Of course she only gets to use them under my supervision (usually when I am making scales or something else).

Yesterday I bought her a toolbox to store the hammer in, and also a pair of pliers and something for which I don't know the english name. It looks a bit like a tiny crowbar for removing small nails and carpet tacks. She has mastered hammering, so now I am going to teach her to remove the nails.

All tools are German quality tools of course. This means they cost 5 - 10 times more than the cheap ones, and for her it wouldn't really make much difference, but I only buy good tools, and I want her to learn to appreciate good tools.

This also means that there is a significant chance I have to share my daddy-dungeon when she gets older. She has her own little workbench next to mine. But then again, there are worse things than being able to share a hobby with your kids.