When reading a dial indicator, what does the difference in reading from top to bottom represent?

The total indicator reading is a key concept in precision measurement, particularly when using a dial indicator. It represents the total amount of variation or "runout" in the surface being measured.

When you read a dial indicator from the highest point to the lowest point, the numerical difference displayed indicates the total deviation from a perfectly flat or level surface. This measurement is critical in ensuring that components are aligned correctly and function as intended in machinery or equipment. By tracking the total indicator reading, you can assess how much adjustment or correction may be necessary to achieve the desired alignment or flatness in your assembly or installation.

In practical terms, accurately interpreting the total indicator reading helps identify any potential issues that could lead to inefficiencies, wear, or failure in mechanical systems, thereby ensuring functionality and longevity.