system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: In most machines and appliances, why does an engineer choose, for example, a Philips head screw for one component but a flathead or hex for another? One would think that what matters are the specs of the screw itself rather than the head.
gpt
The philips head is designed so the screwdriver slips out if you put too much torque (twisting force) on it. So you can safely screw it on full speed with an electric screwdriver, with no risk of breaking anything.

The hex bolt doesn't slip out, so it's useful if you need to screw it really, really tight, or if there is no easy access to the screw, and you can't push against the screwdriver.

The torx head (star shape) is like the hex, but allows even more torque. It doesn't slip, but you have to be really careful or use screwdriver with torque limiter.