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.
A ruptured eardrum is a tear in the thin membrane that separates your outer ear from your inner ear. That membrane, known as the tympanic membrane, is made of tissue that resembles skin.The eardrum serves two important functions in your ear.nother common cause of a ruptured eardrum is poking the eardrum with a foreign object, such as a cotton-tipped swab or a bobby pin that's being used to clean wax out of the ear canal. Sometimes children can puncture their own eardrum by putting objects such as a stick or a small toy in their ear.