Hardened set screws hold parts together without wearing. The small size matched with the hardened nature of the set screw causes it to jam inside the hole of softer steels and aluminium. Stuck set screws often snap from the pressure of removal. Removing a stuck or broken set screw from a part requires a method of removal that softens the screw without causing excessive damage to the threaded hole holding the screw in place.
Turn the head of a hardened set screw counterclockwise with a Phillips screwdriver or Allen wrench. Allow the screw to cool down if it jams in the hole. Turn the screw clockwise 1/4 turn before continuing to remove the set screw.
Install a carbide drill bit slightly smaller than the diameter of the set screw in the chuck of a drill motor if the screw head breaks off the screw during removal. Apply three to five drops of cutting fluid to the end of the drill bit.
Drill slowly into the shaft of the broken screw. Stop drilling and apply additional cutting fluid to the drill bit if you notice smoke coming from the drilling area.
Remove the carbide drill bit from the drill motor when you have a hole 1/4 inch deep drilled into the broken screw shaft. Insert a screw extractor into the chuck of the drill motor.
Set the drill motor to reverse. Set the tip of the extractor in the hole you drilled into the screw. Push the drill motor toward the extractor as you slowly press the trigger of the drill motor and remove the broken set screw from the threaded part.
Wear eye protection when drilling and extracting a broken set screw.