Here is a rare beast, pics of innards of a DAT drum
http://www.diverse.4mg.com/DAT.jpg
top views at top, 1mm squared paper and one of the 1mm screws I used.
The ring of white dots in image lower1 is where the middle ferrite disc
was superglued? to the central boss. I tried 20 seconds of 300 deg C
heat and trying to break the bond with a screwdriver blade, cracked the
ferrite, so the splodges are my superglue additions. 30 seconds of heat
and a smell of varnish or something and the bond broke.