G'day Neil.
Maybe opposing magnets in the de-magnetiser hole cancel any residual magnetism in the screwdriver?
I actually use a cassette head de-magnetiser, left over from my early computing days (when all home brewed software came on cassette tapes). It looks a bit like an 'adult toy' but it sure is effective. Works on the principle of an alternating field (current) reducing in intensity as one slowly moves it away from the tape heads.
I mention this because I just 'resurrected' my first computer, a Z-80 based Aussie 'Microbee' that was hand soldered together in 1983…even the CRT green screen still works! Some of the old cassette tapes were dodgy but the de-magnetiser soon fixed the data recorder. Now back to re-learning Z-80 assembly language and teaching the old girl to talk to an Arduino via a serial shield (horrible name btw, why just not call it an I/O interface)………work in progress.
I am not ashamed to be called a 'Hacker' btw, because way back 'then' it earned a lot more respect than the term does nowadays.
I hope you do not mind me bending your thread a little Neil
Regards from Oz
* Danny M *
Edited By Danny M2Z on 01/11/2014 06:05:11