Deep Hole Drilling Precision and Quality

Deep hole drilling achieves precision that often eliminates secondary operations. Gun drilling delivers IT6–IT9 tolerances and Ra 0.4–0.8 µm surface finish in a single pass at diameters up to 40 mm and depth ratios exceeding 200:1. BTA drilling achieves IT8–IT11 with higher productivity for larger diameters. Hole straightness of 0.001–0.005 inches per foot is typical. Measurement methods include air gauging (two-jet, multi-jet, plunge), CMM with star probes and extension bars, and profilometry. Statistical process control (Cp/Cpk) and in-process monitoring (coolant pressure, torque, thrust force) ensure consistent quality in production.