It's pretty hard to get properly get rid off all data on a hard disk, after several formats or even after rewriting everything on your disk several times with random data it's still possible to recover (some) of your private data.
Our goal was to completely destroy the drive while it was still in the computer case. The theoretical application is to destroy the disk at a moments notice so it won’t fall into the wrong hands. After testing multiple methods, placing about 1 pound of thermite in a clay flower pot and lighting from the drain hole in the bottom yielded the best results. This could easily be placed in the 5.25″ bays above the drive.