On Thu, May 22, 2008 at 10:12 PM, Hoyt A. Stearns Jr. <[EMAIL PROTECTED]> wrote:
> Be very careful with these. Ideally you'll need a special workshop with only > non-magnetic materials around, such as titanium tools, and wooden > workbenches, no computers, disk drives, credit cards, etc. nearby, and > practice being aware of what you're doing. Actually, you missed the most import item to beware of: your watch. I have worked around some strong NdFeB mags and never worry about disk drives and credit cards. I wouldn't sit on a 900 lb NdFeB magnet with my cards in my wallet; but, I haven't had one damaged while working within a couple of feet of some large N50s. And disk drives are no problem at all. Indeed, hard drives have a NdFeB magnet within them. The static field which drives the read/write head is a rare earth magnet. Note, these drives are a great source for Mumetal, a high permeability metal used to shield the magnet from the drive platen. When we demonstrate the Sprain motor we always ask everyone to remove those items, however. Just to be safe. Wouldn't want to be responsible for damaging one of these: http://www.patek.com/patek-philippe.html And I have seen a couple of these on some investors. Yikes! An interesting note: we have a keeper shelf where we store whole and pieces of magnets. Most of what we worked with in the past were N35s. Recently, one worker was moving a N50 near the shelf when a fragment jumped almost a meter off the shelf and imbedded in his hand. He learned the difference between a N50 and a N35 the hard way. :-) Terry
