Yes, pulling the magnets is a PITA. This sounds like a sort of ideal situation though, being given 300 drives to do at once. If you can bring them home and sit in front of the TV while you're doing them it wouldn't be bad. It's a little like shelling peas: kinda boring and the results don't add up very fast.
I haven't done enough of them to wear out a Torx bit, I'm more likely to misplace the Torx set and buy another one. I've got about 30 hard drive magnet halves that I've pulled, and I may not do anymore for a while. Yes, magnet halves. One of the odd things about these magnets is that most of them are made like 2 magnets in one piece of material. One end is usually magnetized North and the other end may also be magnetized North. Flip it over and you'll find the South poles. Sometimes you'll find a North and a South on the same side, but I haven't kept track of how often that happens. If you use some of the magnetic visualization film that Otherpower sells, or sprinkle some iron filings on one, you'll find that there's a distinct line in the middle of the magnet where there's no flux, where the two halves meet. That's where you need to cut or break it. Some people use an angle grinder with a thin cutoff wheel to cut through a stack of them, I just clamp one at a time in a vise with that middle point in line with the top of the vise jaw and give it a whack with a piece of wood. About 90% of the time that works well.
Opening the drives, you may find tape around the edges that you have to peel off or cut. There will be obvious screws on the top that you need to take out. Usually there are some hidden under labels, those you can find by running your fingernail around and looking for places where the label isn't supported by metal. Dig into them with a knife or the Torx wrench to get to the screw. Anything that says removing it will void the warranty is probably worth removing. The circuit board on the bottom can usually be ignored.
Here's a picture of a drive with the cover off, courtesy of the Western Digital website: http://www.otherpower.com/images/scimages/6871/hd_pic.jpg I drew a yellow line around where the magnets are. They sit inside two pieces of steel so you won't see them at first. Usually there are (at least) screws in each end of the top steel piece holding it down. Sometimes once you take those screws out it will feel like there's something else holding it, but it's really just the magnets. See if you can pry it up with a screwdriver. If you can but it goes right back into place it's probably just the magnets. Get a better grip and pry it off. On the underside of that is the top magnet. Some hard drives (notably Maxtor) are so cheap they only have one magnet, most have an upper and lower, some have 2 upper and 2 lower. On the ones with 2 upper and 2 lower you don't have to break the magnets once you get them out.
Underneath the top plate and magnet you'll find the voice coil that moved the heads. You need to get that out of the way somehow. Sometimes you can pivot it out of the way, sometimes you can take off the top screw on the bearing and slide the top of it sideways, in extreme cases with multiple platter drives I've had to take the platter stack apart. Just start with the screws at the top of the stack, lift off the top spacer(s), work the top platter clear of the heads, and keep going. Underneath the voice coil is the bottom magnet, on its own steel plate.
Getting the magnets off the backing plates is another task entirely and I usually set them aside to do later. There are at least 2 ways to get them off (they're glued). One is to clamp the steel plate in a vise in such a way that you can grab the end and bend it away from the magnet. The idea is to bend the steel and the magnet will stay straight. Sometimes. Sometimes the steel plate is really thick (some IBM drives) and won't bend easily. On those I use an old wood chisel, with the flat side of the blade against the steel plate, and push or maybe tap it a little to start it going under the magnet. I've broken magnets both ways. Pulling off bits of the plating is also common.
Once you've got a collection of magnet halves, you'll find you can stack them up and they work the same as a thicker magnet. You won't be able to put them side by side easily though because they'll repel each other. Somewhere on this board there's a post by a guy who built a full-size axial flux windmill with them, but I haven't seen it in a while. Neos seem expensive to buy, but once you've spent a few hours pulling hard drive magnets they begin to look cheaper. But the by-products can also be interesting: the disks are probably aluminum, the head pivot bearings look nicely made, people make anemometers with the motors, and the cases make good small heat sinks. Anyone should take at least a few apart.
Alan
