Hard Disk Drive Magnets

Hard disk drives (HDDs) have become a commodity item over the last 10 or so years. That means that, like most other commodity items, they are considered throw-aways. It seems a shame that at least one, usually two, high qualility neodymium magnets would be thrown away with each dead hard drive.

The reality is that most (especially newer) HDD mags are too small to be very useful for most alternator/generator projects. That doesn't mean I'm ready to write them off as being of no use. For small experiements or proof-of-concept models, they can be very practical. Plus, they can be easy (cheap or free) to get.

If you can get them, old full-height, 5 1/4" SCSI hard drives may contain some seriously strong neo magnets. These magnets



are large, arc-segment magnets that could be placed around the outer circumference of the rotor in an induction motor to alternator conversion. Be careful with magnets as strong as these, I started with 6 of them, but the missing 2 shattered into many pieces when they came together unexpectedly. A little of my blood was mixed in with those pieces.

The most common HDD magnets these days look something like this



and have two poles on each face. To seperate the poles, sprinkle one face with steel filings and two lines will appear.



With a corner edge of a file, scribe down the middle of the lines, through the plating and a little ways into the magnetic material (it works best if you hold the magnet in a vice).

Then place the magnet in a vice such that the scribed line is just about flush with the top of the vice, slap the part of the magnet that's sticking up gently with the file (or similar) and it'll usually snap in two, right along the scribed line.


Then you have two, smaller magnets with a single pole on each side. Use them individually or stack them for increased magnetic flux.