Left extractor
A left-hand extractor (or screw extractor ; also "pig's tail" in the parlance of the metalworking industry) is a tool for unscrewing the remains of broken screws . It has a slim, conical shape and has a rolled or milled left-hand twist over its entire circumference. A tap wrench is required to work properly with this tool .
application
The broken screw is filed flat, center-punched in the thread core and drilled out with a drill about half the diameter. Make sure that the drill is parallel to the thread axis. Then the left extractor is screwed in counterclockwise (left). Because of the conical tip, it will soon get stuck and when you continue to turn the screw, the broken off remainder of the (right-hand thread) screw is unscrewed. The hole must not be too large, otherwise the remainder of the screw will be pushed apart and will sit all the more firmly. Sometimes with very tight screw residues it is also advisable to carefully heat the surrounding material in order to take advantage of the different expansion behavior of different materials.
An impact wrench can be used to remove tight, intact screws .