Comparative burr heights formed on S50C and SS400 steel in drilling process

Abstract

Burr formation is a problem in drilling process as it not only affects quality of products but also increases processing time and operating cost. At the current, burr formation is still unavoidable, and more studies should be performed in order to gain better understandings. As the drilling progresses, the drill is continuously deteriorated, leading to increasing drilling forces and burr heights. In this study, burr heights formed on S50C and SS400 steel at the exit of 4 mm thick workpieces were compared as well as peak forces during drilling process using 8 mm HSS drills. The feed rates were set at 0.01 and 0.03 mm/rev, and the cutting speeds at 25 and 30 m/min. In each condition, 100 workpieces were drilled consecutively and was repeated twice. It was found that the steel type affected the drilling force and burr height. The steel with higher hardness, i.e. S50C, was associated with the higher drilling force especially at later workpieces. The peak force during the drilling process was between 400-650 N and 380-510 N for S50C and SS400, respectively. However, the steel with higher hardness had shorter burr heights; i.e., the burr height occurred on S50C and SS400 was between 0.49-1.31 mm and 0.44-1.97 mm, respectively. For S50C, mathematical relationships can be found between the wear developed on the HSS drill bit and the peak and average drilling forces with promising R2 values between 0.8230-0.9738.