Since 12L14 is an extraordinary machining steel it has become the favorite carbon metal for machining-especially on light weight lathes. It offers inherent ductility combined with finer surface quality. 12L14 has a smooth cold finish (rolled) surface.
1 An infection in the middle ear. When the middle ear is infected, pressure builds up and pushes against the eardrum and can cause the eardrum to perforate. When that happens, you may suddenly notice that the pain and pressure you've felt from the infection stops and pus drains from the ear.  An injury to the eardrum.
Causes of Eardrum Perforation. The causes of perforated eardrum are usually from trauma or infection. A perforated eardrum can occur: 1  If the ear is struck squarely with an open hand. 2  With a skull fracture. 3  After a sudden explosion. 4  If an object (such as a bobby pin, Q-tip, or stick) is pushed too far into the ear canal.