How do I inspect for concentricity (alignment of a cylindrical or spherical part)?

Concentricity is difficult to directly measure without a coordinate measuring machine. However, it can often be approximated to the runout of the part as long as it is circular. To measure this, put a dial indicator on the shaft and zero it. When you spin the shaft, the dial will read zero is perfectly centered, but if it is off center, the dial will oscillate. Here’s a demonstration.