I would like to interface an Amiga 500 floppy drive to an Arduino so I can write ADF images to double density disks. I though I would start off by using a PC 3.5 floppy drive until I'm really sure I know what I'm doing so I don't damage a 20 year old drive. Can I connect an Arduino directly to the drive or should I use a buffer IC or a Floppy Drive Controller IC (NEC D765A/B, Wester Digital WD1771, etc...)?
As long as the disk uses standard sectors, it would seem much easier simply to write the images using "dd" on Linux.
On a PC you already have a drive controller which can write the tracks, it would seem you only need suitable software - which is going to be much easier to find and/ or write, than conjuring it up on an Arduino, for which you really would have to use a WD1771 or such.
{Seem to remember much about the Synertek SY6591 back in the '80s.}
Can you elaborate about "standard sectors". On the Amiga 500 if you format a double density disk, it's formatted at 880k (512 bytes/sector, 11 sector/track, 2 track/cyl, 80 cyl/disk, MFM encoding / decoding). On the PC it's 720k. I'm not aware that you can create a Amiga 500 formatted disk on the PC (Linux) unless you have a Catweasel controller card which are not cheap.
OK, further research (Wikipedia) indicates that the Commodore format is really non-standard and totally incompatible - which means that the NEC D765A/B, Western Digital WD1771 or Synertek SY6591 are going to be of no use either.
Maybe you could use an Arduino to generate and read the data like the Apple II did, but it really looks as if you are on your own here.
Sorry to trouble you. 
Keep Googling!