Cutting Hard Drive Magnets

Wednesday, 13th Jan 2010

hard drive magnets I Managed to get some spare time out in the garage this afternoon to work on some projects. In the end I only spent an hour out there as it was freezing cold! The UK is having a very cold winter this year, not good when working in an unheated detached garage. I did some work on the hard drive magnet diy alternator, didn't get much done though given how cold it was.

I had originally considered using the hard drive magnets as they were, but as hard drive magnets have four poles it seemed to be complicating things so I decided to keep it simple and cut them in half to produce magnets with 2 poles. I would then be able to base my alternator on the more conventenal designs such as Hugh Piggots axial flux design. I had a pile of 12 hard drive magnets to be cut in half, these magnets would then be stacked in pairs to produce 12 magnets that had 2 poles instead of 4. The stack of 12 magnets attached themselves quite firmly to the vice, which made life a little easier.

I thought that cutting hard drive magnets in two would be easy, I expected the metal to be quite soft, in fact it turns out its a bit more of a challenge. My initial plan was to cut them in half with a hacksaw with plenty of oil. My reasoning was that the magnets would not get too hot and the oil would also stop any dust that might be dangerous to breathe. You may already know that hard drive magnets are unusual in that they have four poles. I wanted to cut them in half, but it was impossible to hold the hacksaw steady on the centre line as the magnetic poles were constantly pulling the steel blade to either side.

So I used the dremel to cut a small notch in the centre to use as a guide for the hacksaw blade. I was now getting somewhere, the magnets were harder than I expected, even with the oil there were sparks coming from the blade. I'm not sure if the sparks were caused by the plating on the magnets or the actual magnets themselves. I got about half way through the first magnet when it snapped in half.

hard drive magnets At this point I decided that if the magnets are going to snap anyway I might as well just snap them with pliers. Snapping the magnets was quicker but not without problems. My main concern was sharp fragments flying out, so caution was needed. Some magnets snapped close to the centre, but quite a few snapped unevenly. As this is a low tech, low cost, low power alternator, I'm not going to worry too much about it. The other tricky bit was getting the magnets out of the pliers, the magnets were pulling the jaws of the pliers together, not a major problem but not something I had not considered. If left loose the magnets would would fly around sticking to themselves or nearby objects so a spanner was used for temporary storage.

By now my hands had got far too cold to be messing around with small but powerfull magnets, so time to head back into the house and spend some time on the net checking out Ben's excellent GotWind website and forum. All the details on progress so far can be found on the DIY Alternator HDD1 page.