On 26 Nov 2006 at 13:16, Fred Cisin wrote: IIRC, it wasn't the diskettes so much as the clamping arrangements on the drives (Shugart had the most reliable system, but sued anyone who tried to copy it). It was quite awhile before someone figured out that turning the spindle motor on when a diskette was inserted so as to center the hub in the clamping setup was a stroke of genius. I've got some old Micropolis single-sided drives that will mangle a hub in fewer than 10 insertions. A few HD manufacturers put the hub reinforcement on their disks early on. I didn't think it did any harm, but it didn't help either and was nonstandard. I recall getting a very angry call from a customer who said that CopyQM was making unreliable 5.25" DSDD copies--that he'd make and verify a copy and then found it couldn't be read by another machine. What he didn't mention is that he was using the PolyPak equivalent of diskettes--no-name mail-order cheapest possible. I asked him to send a few of the failures our way and we'd have a look at them. It turns out that whatever bit of machinery that was used to apply reinforcing rings had applied TWO to each side, each ring being slightly offset from the other. The diskettes would never center on the hub the same between any two insertions. After I pointed this little tidbit out to him, the complaints stopped. Cheers, Chuck