Everyone has to start somewhere, and that's the philosophy behind the phrase cut your teeth. To cut your teeth on something means to gain your first significant experience. Someone who is a trained chef, for example, might have gotten his start flipping hamburgers when he was a teenager. A computer expert could have done so working on the first Apple II PCs. Whatever a person's field of expertise may be, he most likely cut his teeth working with less sophisticated equipment at an early age.
The expression cut your teeth most likely evolved from the sometimes painful realities of human dental development. Many young adults experience an eruption of third molars known as "wisdom teeth." Sometimes the eruption, or cutting, of these wisdom teeth is a relatively painless experience, but other times a painful crowding situation arises. These extra teeth may have to be surgically removed if their presence becomes problematic. Because the eruption of wisdom teeth or "eye teeth" often coincides with a young adult's first real work experience, the association between the two rites of passage most likely seemed inevitable.
Cutting your teeth on a particular machine or entry-level project may or may not be a satisfying experience at the time, but it often prepares you for more challenging duties. A professional chef in training, for example, may start out making salads or appetizers at a small restaurant. The job itself may be very demanding or repetitive or tedious, but if the chef should ever have to fill in for a missing salad maker years later, he or she would have the necessary skills to do it. By starting with basic equipment and procedures, you often develop a sense of mastery that could prove useful as your career advances.