Analysis of geometric dimensioning and tolerancing in sustainable hard drilling using vegetable oil-based MQL

This study investigates the influence of cutting parameters on the hole precision in hard drilling of AISI 4340, with a particular emphasis on vegetable-based minimum quantity lubrication (MQL) as a green machining approach. The effect of key parameters including cutting speed, feed rate, and workpiece hardness was analyzed on the cutting force and hole precision using soybean oil as the cutting fluid. The results showed a stable trend in the time history of cutting forces during the cutting process, with no significant wear or other disruptions, indicating that vegetable oil can provide effective lubrication during hard drilling. The axial cutting force was lower than 8000 N in the studied range of cutting parameters. The findings also revealed that feed rate is the most important factor influencing output characteristics, which deteriorated hole diameter, circularity, and cylindricity tolerances of up to 200%. This is especially evident with softer materials (30 HRC). Furthermore, workpiece hardness had a minor effect on circularity, but a significant impact on straightness and overall cylindricity up to 56%. Soybean oil-assisted MQL resulted in tolerances magnitude of less than 60 μm, demonstrating its effectiveness in hard drilling AISI 4340.