Another comment mentions a KryoFlux. A cheaper alternative is a GreaseWeasel (£30, $30). The 4.1 version even has USB-C as a connector. You will need an external power brick with a 4pin Molex connector for 5.25 drives. You can buy these standalone or they might come with a SATA/PATA/IDE Hard Drive to USB converter. Can also use an old PC power supply if you fake the power on signal.
I've had quite a lot of success, almost 100%, over quite a long time - both 5.25 and 3.5. I did use older drives intended for "desktop" machines. The drives from Japanese companies seem to be the most reliable; NEC, TEAC. The 3.5 USB Portable diskette drives are based around laptop floppy designs. You won't be able to find a direct 5.25 to USB adapter (or modify one to work) as the speeds / data rates are all wrong, so you will need something like a GreaseWeasel or old PC for those.
I've used different reading mechanisms over the years; an old PC running Linux with a real floppy chipset + custom raw reading code, custom hardware with an F82077 + Atmel + SDCard, and most recently a GreaseWeasel.
The floppies I've recovered were stored relatively well, but were mostly my and family members data - not commercial floppies. If there is any copy protection on the floppies you are trying to read you may need to capture the flux transitions. For these, I'd check archive.org to see if someone has already generated a copy.
For 5.25 floppies fingerprints and surface blemishes can be softened / removed with ISO Propyl and a Q-tip. Floppies designed for cleaning the heads of drives seem to now be very expensive / non-existent. Manually cleaning the heads of a 3.5 drive is way more difficult. I've got ideas about using Face mask / filter material to create a cleaning tool, but it is on the experiments to try list.
Even back when floppies were a thing, I found that 3.5 drives were more un-reliable between machines than 5.25 drives. I think there was more variation in head alignment and track positioning. When I've had issues, I've always been lucky in that switching the drive vendor / model made reading the floppy possible even if it took multiple attempts or was very slow.
The floppy interface for 5.25 is largely the same as 3.5. The data rates are the same. The only functional difference is fewer sectors per track because of the faster motor speed. That's all accounted for with a FDC interface controlled by a BIOS that knows what each drive is. A USB FDC bridge is stuck on its firmware and has no way to adapt to alternate track layouts it isn't designed to handle.
kinda crazy that just switching drives can make an unreadable disk readable
makes me wonder how many old floppies got written off as dead when it was really just an alignment mismatch
In the early 80s this was a fairly common thing that was known to happen with floppy disks where some manufacturers drives could not read disks written by other manufacturers even though in theory they were compatible and used the same standard. Usually floppy drive manufacturers test their drives against diswritten by whoever made the computer. So if you had an Atari, then anything written with an Atari drive could be read by any other drive you could connect to your Atari computer but if you had off-band drive, even if it was otherwise a good drive, there was no guarantee that a different drive could read that. This problem really came to head when manufacturers started going into different density drives. The early double density drives often didn't work with anyone else's drive, so when higher density became common, you really saw a lot of problems because people were trying to share this written by different drives. (and then there was Atari's oddball enhanced density drives that nothing could deal with for a few years.) you saw the same thing with Apple, Commodore, and probably with the PCs too, but I didn't know anyone who had those.
Tape drives were even worse for a long time. In many cases in the 80s and even into the 90s, sometimes a different drive from the same manufacturer couldn't read your tape.
Comments
Another comment mentions a KryoFlux. A cheaper alternative is a GreaseWeasel (£30, $30). The 4.1 version even has USB-C as a connector. You will need an external power brick with a 4pin Molex connector for 5.25 drives. You can buy these standalone or they might come with a SATA/PATA/IDE Hard Drive to USB converter. Can also use an old PC power supply if you fake the power on signal.
I've had quite a lot of success, almost 100%, over quite a long time - both 5.25 and 3.5. I did use older drives intended for "desktop" machines. The drives from Japanese companies seem to be the most reliable; NEC, TEAC. The 3.5 USB Portable diskette drives are based around laptop floppy designs. You won't be able to find a direct 5.25 to USB adapter (or modify one to work) as the speeds / data rates are all wrong, so you will need something like a GreaseWeasel or old PC for those.
I've used different reading mechanisms over the years; an old PC running Linux with a real floppy chipset + custom raw reading code, custom hardware with an F82077 + Atmel + SDCard, and most recently a GreaseWeasel.
The floppies I've recovered were stored relatively well, but were mostly my and family members data - not commercial floppies. If there is any copy protection on the floppies you are trying to read you may need to capture the flux transitions. For these, I'd check archive.org to see if someone has already generated a copy.
For 5.25 floppies fingerprints and surface blemishes can be softened / removed with ISO Propyl and a Q-tip. Floppies designed for cleaning the heads of drives seem to now be very expensive / non-existent. Manually cleaning the heads of a 3.5 drive is way more difficult. I've got ideas about using Face mask / filter material to create a cleaning tool, but it is on the experiments to try list.
Even back when floppies were a thing, I found that 3.5 drives were more un-reliable between machines than 5.25 drives. I think there was more variation in head alignment and track positioning. When I've had issues, I've always been lucky in that switching the drive vendor / model made reading the floppy possible even if it took multiple attempts or was very slow.
Good luck.
The floppy interface for 5.25 is largely the same as 3.5. The data rates are the same. The only functional difference is fewer sectors per track because of the faster motor speed. That's all accounted for with a FDC interface controlled by a BIOS that knows what each drive is. A USB FDC bridge is stuck on its firmware and has no way to adapt to alternate track layouts it isn't designed to handle.
kinda crazy that just switching drives can make an unreadable disk readable makes me wonder how many old floppies got written off as dead when it was really just an alignment mismatch
In the early 80s this was a fairly common thing that was known to happen with floppy disks where some manufacturers drives could not read disks written by other manufacturers even though in theory they were compatible and used the same standard. Usually floppy drive manufacturers test their drives against diswritten by whoever made the computer. So if you had an Atari, then anything written with an Atari drive could be read by any other drive you could connect to your Atari computer but if you had off-band drive, even if it was otherwise a good drive, there was no guarantee that a different drive could read that. This problem really came to head when manufacturers started going into different density drives. The early double density drives often didn't work with anyone else's drive, so when higher density became common, you really saw a lot of problems because people were trying to share this written by different drives. (and then there was Atari's oddball enhanced density drives that nothing could deal with for a few years.) you saw the same thing with Apple, Commodore, and probably with the PCs too, but I didn't know anyone who had those.
Tape drives were even worse for a long time. In many cases in the 80s and even into the 90s, sometimes a different drive from the same manufacturer couldn't read your tape.
thats wild, didnt know it was that common kinda funny to call it a standard if ppl still couldnt reliably read each others disks lol