What is the purpose of a gage block?

• A. To calibrate and verify measurement instruments with highly accurate, known dimensions.
• B. To measure hole depth.
• C. To hold the workpiece during milling.
• D. To check surface roughness.

Answer: (A)

Gauge blocks are precision length standards used to establish and verify the accuracy of measurement instruments. Their purpose is to provide highly accurate, known dimensions that can be used to calibrate tools like micrometers, calipers, height gauges, and dial indicators. By wringing blocks together, you can create precise reference lengths across a range of sizes, ensuring instruments read correctly. Their dimensions are tightly controlled and traceable to national standards, making them the go-to reference for calibration and setup in both shops and labs.

They aren’t used to measure hole depth, hold workpieces during milling, or check surface roughness; those tasks rely on depth gauges, vises or clamps, and surface roughness testers, respectively.