I've taken old HDDs to a commercial shredding service. They have a special shredder for electronics and will let you watch your drives/tablets/etc being destroy

I've taken old HDDs to a commercial shredding service. They have a special shredder for electronics and will let you watch your drives/tablets/etc being destroyed. I think it is a pretty common service, there are quite a few places that do this in my city. Does get expensive if you have a bunch, though.