To destroy the disk by taking it apart (and ending any possibilities of data recovery) a Torx-8 should fit most of the screws.
After disk dis-assembly, attempted repair, and reassembly keep the screwdriver handy.
That way, when the disk will completely fail to work all, you can take case, platters, etc. all apart again.
Two reasons why:
1) Salvage the magnet (very powerful and useful) then responsibly recycle the other components.
2) The disk platter(s) can be used as reflectors and mirrors.....
Those are the reasons I take a HDD apart.
(Afterthought: I once did some experimenting with the motors but will not count that as a reason.)
As stated, once the disk is opened, there will be no data recovery.