M1.2 x .25mm pitch x 13/16 OD HSS Round Adjustable Button Die
Use metric button dies to clean up damaged or worn threads on eyeglass screws, or to create new threads on unthreaded parts.
Place the screw into a pin vise to hold it as you turn the die clockwise. The die should catch on the threads already cut into the screw. Every couple of turns reverse the die about half a turn to clear the threads. This will help to give you cleaner, stronger threads.
Cutting metal with metal creates friction and heat. A few drops of cutting oil on the screw will help reduce the friction and the chances of heat-damaging the delicate threads. Re-apply the oil as necessary.