Or more specifically after you’ve used some Torx head screwdrivers and extracted the platters from you hard drive.
Anyhow smaller drives tend to use glass platters. And sure as shit the dead hard drive I removed from my Linux box had glass platters. You can test this – just hold a magnet to it. If the magnet is attracted to the platter it’s metal, otherwise glass.
In the case of metal – a 20 to 50 grit sandpaper is your friend. In fact for both metal and glass a vigorous rub with sandpaper will render it unreadable.
But in the case of glass you can go one step further. Smash the shit out of it with a blunt object. You’ll end up with something similar to this: