This is the process of lathe machining and the steps to be followed

Use 90 degree lathe, 3 mm cutter, hand-sharpened r cutter, center drill. First clamp one end, punch the center hole, top turning out the outer circle 25 38 50, leaving 0.4 allowance, then turn around and punch the center hole. Top turning diameter 40 also leave a margin. Then use a 45 degree cutter to turn a taper the same as the top. Double top turning to size. If you use a pulling disk, you can be a cut in place. If the direct top, a knife up to 0.2 otherwise with the turn