Can't mount, see or reformat external USB drive

[macstatic]

I've been messing around with an external 2.5" SATA hard drive which I put in an empty USB enclosure in order to try to install Windows/Bootcamp on it and now the drive doesn't even show up in Disk utility.

I believe the reason is because I interrupted a failed installation/formatting in Windows or something. When I now attach the USB drive to my Mac it spins up but neither appears on the desktop, alerts me that the drive needs to be initialized or as I said above doesn't show up in Disk utiility (so I can't reformat it). By the way: regarding Disk utility it won't show anything (not even my regular Mac HD drive) until I physically disconnect the external USB drive by pulling out its USB cable.

So I've searched the web for help and tried out some Terminal commands. This is getting me somewhere, but I still haven't found a solution.

$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Mac HD                  2.0 TB     disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk1 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *500.1 GB   disk1
   1:                 DOS_FAT_32 WINDOWS                 500.1 GB   disk1s1

$

So this means the disk is physically there and identified as /dev/disk1 which is good!
Next I try to format the drive using these commands:

$ diskutil eraseDisk JHFS+ Untitled /dev/disk1

This appears to work, but after a while I get this error message:

Started erase on disk1
Unmounting disk
Error: -69877: Couldn't open device
$

I looked this up online and my understanding is that I need to properly unmount it first, so I try this:

$ diskutil unmountDisk /dev/disk1
Unmount of all volumes on disk1 was successful
$

At this stage I expect something to happen, but it still won't show up on the Finder desktop or in Disk utility.
Is there something else I can try in order to reformat/partition the drive?

 

[macstatic]

Something happened!
While finishing the above posting I had Disk utility continue running for a couple of minutes, and once I checked it out again the Windows drive was there! I will now try to reformat it and see what happens.

 

[macstatic]

Interesting progression...... I was actually able to reformat the drive this time (I chose MS-DOS). This took forever to do, but despite my suspicion of a faulty drive I hung in there and let it finish the job (which resulted with a successful format, according to Disk utility).
I tried ejecting the drive after that, then remounting it. This too took forever (or so it seemed) for the drive to mount on the Finder desktop. When it did I returned to Disk utility, reformatted (erased) the drive again but with the standard Mac HFS format. Now the drive acted normal again.

So, bottom line: when formatted to MS-DOS everything takes a lot longer. Does this appear corrrect?

 

[MBAir2010]

did you try formatting to MOS Do- oh, you did
I'm doing the same thing with a usb 32 GB thumb drive from 2012

 

[macstatic]

Are you trying to install Windows as well?
I'm trying to find a way I can install it on a separate drive without needing to install MacOS first, but haven't quite figured that out yet despite following various online "how-to" pages.