Massachusetts businesses that rely on workers with specific technical skills are finding that potential employees are in short supply. A lack of machinists, for example, and a dearth of mechanical engineers, are making it difficult for manufacturers to staff up. Some have observed that occupations traditionally considered "beneath" young college graduates are now requiring intelligent workers with problem-solving skills and the ability to work with their hands. "Those used to be skills that were passed down from generation to generation,” said Mary E. FitzGerald, human resources manager for Saint-Gobain Corp.'s ceramics and high performance refractory operations in Worcester, MA. “You just can't find those skilled people anymore."