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.
Etiology. Infection is the principal cause of tympanic membrane perforation (TMP). Acute infection of the middle ear may cause a relative ischemia in the drum concurrent with increased pressure in the middle ear space.This leads to a tear or rupture of the eardrum that is usually preceded by severe pain. If the perforation does not heal, it leaves a residual tympanic membrane perforation (TMP).nfection is the principal cause of tympanic membrane perforation (TMP). Acute infection of the middle ear may cause a relative ischemia in the drum concurrent with increased pressure in the middle ear space.