How do you dispose of your dead (spinning platter) HDDs?

You can take them apart with the right tools, they have a weird screw head but any decent pc repair kit should have the right attachment. You can actually remove the platters, generally doing that and tossing the lot in the recycle place is fine, good luck to anyone trying to put them back and get it to work but for an extra measure give the platter a little buff with sand paper or just scratch it good.

I've done it a bunch of times and it is actually kind of fun

If you have a drill press you can just drill a hole through it. if you're my Dad you take it out to the back 40 and shoot it .

I used to pay a company a £100, I think, and they came in a lorry and they ground the disks in a machine. I enjoyed the fact there was a venerable stick to ram into the machine when the mechanism got blocked. From a security point of view you observed the destruction and got a certificate as a paper trail. I used to keep a sample of a ground disk on my desk. The company also got the kick back of melting the disk down to recover the minerals.

First I try to wipe them, then I remove the processing card, or severely damage it. Then I take them too the dump, they have an electronics bin.

If I was worried about the data falling into the wrong hands, i.e. I had a lot of money, I would consider some method to ensure they were destroyed. At my work, we send the disks off to be shredded.

Go ask a Drive Recovery service about the things they've recovered from units that have been treated like suggested here.

The methods you folks are suggesting are not nearly as secure as you think.

1. Secure in bench vice 2. Impact drill

I always take a big nail and hit that through the unit, beyond repair after that.

Step them. Make sure to stomp on the platters.