Angle grinding through a 3.5" hard drive case, spinning platter and controller electronic circuitry will produce enough heat and metal scraps to produce an absolutely unrecoverable hard drive. The magnetic coating containing the actual data doesn't like any kind of dirt, metal chips nor rapid heating.
Funny thing: One of the IBM drives was from era of glass platters. I had no idea about that at the time. Ear protection and noise made sure of that. Afterwards the glass platter was shattered into small pieces making the hard drive sound like a jingle bell. There was a small time slot when glass was used in drives to improve data density. Later manufacturers learned to smooth the aluminum platters beyond glass ones and abandoned the brittle materials.