IT had me drill holes in a dozen hard drives and then scrap them.
I took them apart and want to separate the magnets from their retainer brackets. They are glued in and the one I put a propane torch on to break the glue bond was far weaker than the one I twisted apart.
The one I twisted apart had the plating flake off.
What is a good way to disassemble these?
Bend the brackets - the magnets will break off quite cleanly.
That is, bend them away from the magnet. This is quite easily achieved by inserting a strong, well-fitting screwdriver through each of the two main mounting holes, then pulling them towards/across each other.
Be careful with those magnets - they will injure you if you get skin trapped between them when they snap together.
The one I twisted apart had the plating flake off.
Perhaps this magnet was not properly prepared for plating.
What I did was clamp one end of the bracket in a vise and twist the other end with a adjustable wrench sized down to the brackets thickness.
You can sometimes use a hammer and chisel to knock them out, but you have to be careful. Too light of a tap and the magnet won’t break free. Too hard and you can crack the magnet. Depending on how strong the glue is you might still have a problem with the plating coming off.
Heat is about the best thing I know of to weaken the glue, but a propane torch is overkill. You don’t want to heat the magnets up too much or you’ll ruin them. Use something like a hair dryer or a paint stripper, and wedge the magnet off with a screwdriver or knife while you are heating it.
There may be a better way than that, but I’m not aware of it.
Depending on how they’re attached and what they’re plated with, some damage may be inevitable, unless you’re able to clamp the thing down and remove the bracket with a milling machine or some such.
Personally, I prefer to keep them mounted on the brackets, as this makes them much easier to handle and mount (and separate if they should stick together).
Generally, the magnets are glued to the retainer plates and then the whole assembly is plated to seal them - you need to break the plating to get the magnets off. The rest of the plating will peel off the magnet - it is non-magnetic and the surface of the magnet does not bond strongly.
Si
This.
Be careful they will pinch the crap out of you if you get between them and something they are attracted to.
Also, handling the magnets with flaky chrome is really risky - you may not just trap some skin between the magnets, but you may end up sliced by a flake or splinter of the coating.
Si
Yes, I have the “Blood Blister Of Experience”. 
What do you do with a hard drive magnet?
They make great refrigerator magnets for thick stuff like calendars and memo pads. You can also test the black ink on U.S. currency with them. They’re great for quickly erasing/destroying old floppy discs and screwing up the colors on CRT televisions.
I put a magnet next to the CRT on our TV to show my wife the effect. I removed the magnet and the picture was still screwed up.
“Please, please let this TV have a strong degaussing function on start up” I said as I shut it down.
I’m still posting so the start up must have demagnatized the frame that I magnetized.
I am working on a solar pendilum that gives the swinging weight a kick , powered by a solar cell, that works best with a strong magnet.
I took apart an Ikea magnetic knife rack and inside the two outer metal layers were broken hard drive magnets spaced across the length of it.
They’re good for science experiments - I made thiselectric motor with my son - it used to be the case that a crude motor like this one was tricky to get adjusted and working, but the really strong magnets make the whole system a lot more forgiving of other engineering shortcomings.