In the production process of disc parts, in order to ensure the verticality of the process reference, the craftsman often asks the benchmark for the circular runout of the end face. In order to meet the requirements of coaxiality on the drawings of shaft parts, it is customary to use radial round jump instead of coaxiality during machining. In fact, the craftsmen are unknowingly using the measurement jitter principle to quickly and economically test the product. In order to ensure the product quality and improve the process qualification rate, whether this alternative method is accurate and reliable, and how to grasp it is a problem that the craftsperson deserves to discuss together.