Deep Hole Drilling of AISI 316 Steel using CNC Peck Drilling Approach and Parametric Study

Drilling is a crucial machining process in manufacturing, often used for assembly purposes. Assembly challenges develop as a result of inappropriate hole geometry, such as circularity, perpendicularity and cylindricity regardless of whether the tolerance is within the limit. Deep hole drilling is a specialized technique to create holes with high depth to diameter ratio. In various industries, such as oil and gas, shipbuilding, and aerospace, deep hole drilling of stainless steel is performed to make components like drill collars, rotor shafts and fuel injector nozzles. This study investigates the impact of drilling process parameters on the hole quality, using Taguchi design of experiments for AISI 316 drilling optimization. Deep hole drilling experiments were carried out based on a Taguchi L9 array, with 3 different drills (HSS, M35, TiAlN); at 3 different cutting speeds and feed rates. The innovative concept of intermittent drilling and retraction is applied using CNC vertical milling machine and the results are examined for the achievable tolerance on size and geometry. Results indicate that the cutting tool material is the most significant factor influencing roundness, cylindricity, and hole size, followed by feed and speed. Speed has a lesser effect on perpendicularity compared to the cutting tool type and feed. Feed exerts a greater influence on surface roughness than the cutting tool type. Chip morphology indicates HSS drillbit is effective and stable in the process of producing quality holes.