Millwright Level 1 Practice Exam 2026 - Free Millwright Practice Questions and Study Guide

Before using a gauge block, it is crucial to remove the rust preventative compound. Gauge blocks are precision measurement tools made from high-quality materials that can be sensitive to contaminants like oil, rust preventatives, or any foreign substances. These compounds are typically applied to gauge blocks to protect them from corrosion during storage and transport.

Using a gauge block with residues from rust preventative can lead to inaccurate measurements. It can interfere with the proper contact surface between the gauge block and the parts being measured, potentially resulting in measurement errors. This is why it is essential to ensure that the surface of the gauge block is clean and free from any oils or coatings before it is used in precision measurement applications.

Although the inspection for scratches is a valid consideration and essential for ensuring precision, the immediate action that must be taken before usage is the removal of any rust preventative to maintain measurement integrity.