one thing about changing platters on a voice coil drive.

if its a multi platter drive, FORGET IT. its easier to change the heads than the platters. because if you undo the platters, if the two platters slip any at all (which they will, without a piston compressor or platter tool). you will loose the cylinder and servo track alignment, and there goes your possibility to recover data... down the drain.

so you need to watch for that. its far far easier to change the head/actuator and swap between two identical drives than it is a multi platter.

the tolerances between platter to platter alignment tracking and head pressure bering is a micron or less.