What is a common mistake regarding bore gage calibration? Every bore gauge needs to be set to match a master standard before it is used. A common mistake is when users do not purchase and use a setting master for this process prior to the first use of a new bore gauge. Whenever a new bore gage is purchased, a setting master ought to be purchased as well. Setting rings, micrometer, and master setting kits can all be used as master standards to complete the bore gage calibration procedure. If the step of matching a bore gage to a master standard is skipped, then the gage will be used without being properly set and all measurements taken run the risk of being inaccurate. If you are a new bore gage owner, or are looking to buy one in the future, remember to complete the bore gauge calibration procedure before using your new tool.