Checking Drill Rod Wear with Vernier Caliper Today, we compared our new drilling rods (7.2 mm) with old rods (6.8 mm) using a vernier caliper. That slight reduction in diameter may look small, but in drilling, it means metal fatigue, weak joints, and potential pipe cuts at greater depths. Why This Practice Matters: 1.Ensures rod integrity and prevents sudden breakage during deep drilling. 2.Helps plan timely replacements and avoid costly downhole losses. 3.Improves drilling efficiency and safety