Date   : Thu, 07 Mar 2013 16:26:37 -0000
From   : profpep@... (Mike Pepper)
Subject: 5.25" DSDD / QD (96tpi) Floppy Disks

> Anyone need any 5.25" floppy disks?
>
> I have just been given three large crates full - I estimate somewhere 
> between 2000 and 3000 disks.
>
> All of them are either marked Double Density or "Quad Density" which I 
> believe is a marketing term for Double Density 96tpi. They should all work 
> perfectly in BBC drives, or any other DD drive.
>
> The vast majority are Inmac branded, but there are a few other brands in 
> there as well.
>
> The catch is that I was given them with the strict proviso that I must 
> wipe them before passing them on to any third party, so I will need to 
> re-format them before giving them away, so if you want a large quantity 
> I'll have to make a small charge to cover my time!
>

You can make then unreadable with a home made bulk eraser - I had to do a 
big batch once. A transformer core, or a big contactor solenoid will do it; 
You need a biggish AC coil, and and core section open at one end. I ran mine 
up on a variac, to limit the current. Just wipe the discs across the open 
end. I have seen some for 5,25 floppies done like a post box, they just drop 
the discs through a slot which passes them through the strong AC field.

I expect a couple of passes with an old disc drive actuator magnet might 
have the same effect on making them unusable - might be worth a try, because 
it is certainly faster.

HTH

Mike