Machinability Testing Method Using Face-Milling of Cylindrical Workpiece

Conventional machinability testing requires large numbers of workpiece specimens. The difficulty is evaluating the machinability rating of an unknown and newly produced work material. A new method, proposed in this paper, is to face mill an end face of a cylindrical workpiece. The (VT)^n=C curve is then determined from the data. Using this curve a machinability rating for the work material can be found. This method uses 85% of the workpiece for chip making as compared to 45% with conventional methods. From face milling a JIS S45C steel bar, the exponent n is found to be 0.35. This value is satisfactory when compared with the value obtained by using the conventional method. Using these techniques a subsequent investigation was conducted using JIS S12C. Materials' properties were varied by changing the chemical composition and heat treatment. After the test runs, the following conclusions were reached : 1) A small workpiece diameter (up to 2.5cm) can be used without altering resutlts. It should be noted that homogeneous properties of the workpiece remain essential. 2) There is little change in chip thickness, when a 5.5cm diameter workpiece is cut with 25cm milling cutter, since the centers of the two elements coincide. 3) Wear pattern on the tool face is rectangular in form, and the repeatability of the wear progress is very high. We conclude that error in measuring the wearland is small, even when observed by different operators. 4) A graph of cutting time vs. wearland is a straight line