Level 3 Engineering Fitter Practice Exam

Center drilling establishes a precise starting point for the hole. The center drill creates a small, well-centered pilot that guides the twist drill as it begins cutting, which greatly reduces drill wandering or walking off axis when you’re drilling into the workpiece. This initial, accurate spot is essential for getting the final hole in the right location and straightness. After the center hole is made, the twist drill enlarges the hole to the desired size. Center drilling is not for finishing or for enlarging the hole to final size by itself, and the twist drill does not serve to create a pilot for center drilling—the center drill sets the pilot first.