1 is a jet nozzle having a small end diameter of 3 mm, a large end diameter of 15 mm, a length of 150 mm, a surface roughness R_a1.6, and a workpiece material of high tensile brass. This piece is difficult to machine and requires high precision. It is difficult to complete with normal turning. To this end, we milled a Φ15mm ordinary drill into a tapered shape with a small end Φ3.5mm, and then grinded the land and the back corner on the tool grinder. Drilling with this drill bit, drilling depth 148mm, to ensure the wall roughness