Axial runout is the variation of a circular feature along its axis of rotation. It measures how much the feature wobbles or shifts in the direction of the axis. For example, if you have a disk with a hole in the center, axial runout is the difference between the highest and lowest points of the disk as it rotates around the hole. To measure axial runout, you need to establish a datum axis, which is a theoretical line that represents the ideal axis of rotation. The datum axis can be derived from a cylindrical or conical feature, such as a hole, a shaft, or a cone. Then, you need to use a dial indicator or a similar device to measure the distance between the datum axis and the circular feature at various points along the axis. The axial runout tolerance is the maximum allowable variation of this distance.
Radial runout is the variation of a circular feature perpendicular to its axis of rotation. It measures how much the feature deviates from its ideal circular shape or diameter. For example, if you have a wheel with a rim, radial runout is the difference between the largest and smallest radii of the rim as it rotates around the hub. To measure radial runout, you need to establish a datum axis, as in the case of axial runout. Then, you need to use a dial indicator or a similar device to measure the distance between the datum axis and the circular feature at various points around the circumference. The radial runout tolerance is the maximum allowable variation of this distance.
