[Lynn Eades]

Dave, Depending on what state your captive nuts are in you may be able to tidy them up by cutting a groove in the thread of another bolt (cut off disc etc) If you lube (a bit of kero mixed with a bit of oil) and judiciously work your grooved bolt into the captive nut, you will likely clean it up. Don't force it. back off add more lube and have another go.
Btw,fyi, most fasteners have a rolled thread which is stronger than a cut thread. It means the "grain" in the material follows the shape of the metal. The captive nuts were likely "cut" via a nut tapper. (just my guess)
If the threads are stripped you will need to replace the captive nuts. Seek out the right ones and take them back to original.