*3.3. Tool*

Two drill-milling tools characterised by different geometries were developed and employed for the experimental tests, to compare their performance. The characteristics and geometry of the two tools are shown in Figure 4. The first tool, T1, is made of tungsten carbide (WC) and has a 6 mm diameter and 100 mm length; the drilling portion is 8 mm long, with two cutting-edges, a 120◦ point angle, and a 20◦ helix angle; and the milling portion is 18 mm long, with three flutes, a 15◦ helix angle, a 10◦ rake angle, and a 7◦ clearance angle. The second tool, T2, is made of tungsten carbide (WC) and has a 6 mm diameter and 100 mm length; the drilling portion is 8 mm long, with two cutting-edges, a 120◦ point angle, and a 20◦ helix angle; and the milling portion is 18 mm long, with five flutes, a 20◦ helix angle, a 10◦ rake angle, and a 7◦ clearance angle.


**Figure 4.** Comparison of the two newly developed drill-milling tools and milling portion geometry parameters (ha—helix angle; ra—rake angle; ca—clearance angle; Z—flutes number).
