What causes broken screws to break?

Broken screws are a common problem for do-it-yourselfers. It can be maddening to try to remove a broken screw and takes time, patience and concentration. The most common reason a screw will break is because it is the wrong type of screw for the application you are working on. For instance, you should not use a drywall screw when building cabinets or installing hard wood shelving. Using the wrong type of metal screw, such as an aluminum screw, for wood construction on wood that is very heavy can lead to breakage. Putting too much pressure on a screw when using an electric screwdriver is also another common reason for a screw to break.