This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A screw Will often break off in a piece of work in such a manner that it is quite impossible to remove it by using a pair of pliers or a wrench. In this case the following method is very efficient and expedient.
Drill a small hole in the screw as near the center as possible. Roughen the edges on the tang of a file with a cold chisel, and drive the tang into the hole with a mallet. The roughened edges of the tang exert enough friction on the metal to remove the screw by turning the file in the proper direction.