I stumbled upon some videos showing real brain surgeries and noticed how the surgeon often uses a hand-held drill to create a hole in the skull (for accessing the brain). This made me wonder:
How does the surgeon ensure that the drill doesn't drill deeper than they want, thus damaging the brain?
For example, just from drilling holes in wood, I know that at the moment the wood is completely punctured through, the drill jerks forward deeper into the hole (since my hand is still applying a force forward, and my reaction time isn't quick enough to stop my hand immediately after the wood is completely punctured). What prevents this from occurring during surgeries?