I have ~10 HDDs that I’d like to dispose of. For a while, I tended to buy unwarrantied used disks for my NAS, so these have all failed in some form or another over the years. I can’t just toss them, because they have my (unencrypted) data on them, but I can’t wipe them either since they don’t mount anymore. I want a simple and reliable way to render the contents unrecoverable. A nation state is not part of my threat model, but any kind of data reconstruction that could be bought with civilian money is.

I’ve tried:

• Smashing with tools (largely ineffective)
• Punching holes with a drill press (how many holes are needed to ruin the disk? Also I’ve broken/dulled a few bits doing this)