Maintains specifications by milling, drilling, grooving and cutting, taking measurements; detecting malfunctions; trouble shooting processes, identifying and sharpening/replacing worn tools; adhering to quality assurance procedures and processes. A function may be essential for any of several reasons, including: the job exists to perform that function, the employee holding the job was hired for his/her expertise in performing the function, or only a limited number of employees are available to perform that function.