What is the component of a dial indicator that must be zeroed out before any readings can be taken?

The bezel of a dial indicator is the adjustable component that allows the user to set the indicator to zero before taking any measurements. This function is critical because it establishes a baseline or reference point from which all subsequent measurements will be taken. By rotating the bezel, the user can align the needle on the dial face to the zero mark. This ensures that any readings taken afterward are accurate and reflect the actual changes in distance or position relative to that set point.

In contrast, while the face displays the measurement and the plunger contacts the workpiece, they do not serve the same purpose in zeroing the device. The plunger, which extends and retracts as it measures thickness or depth, must be in contact with the object being measured, but it does not have an adjustable feature to set zero. The indicator itself refers to the complete unit, and therefore does not have the specific functionality to zero out the readings. Thus, the function of zeroing is specifically attributed to the bezel.