What is an indicator used for in machining?

An indicator is a precision measuring tool commonly used in machining to measure small distances and ensure the accuracy and precision of components. Specifically, a dial indicator can provide precise readings of distances and can detect minute variations in height or diameter, which is crucial for making fine adjustments during machining processes.

Using an indicator helps machinists verify that parts are within specified tolerances, ensuring that the dimensions are exact as per engineering drawings. This functionality plays a vital role in maintaining quality control in manufacturing environments, where even the smallest deviation can affect a part's performance or lead to assembly issues.

The other options do not accurately capture the primary function of an indicator. While increasing cutting speed, reducing machine vibration, and checking coolant levels are all important aspects of machining, they are not related to the specific use of an indicator, which is primarily focused on measurement and precision.