code: def get_drill_bits_d_metric():
      
      return np.concatenate((np.arange(1.0, 10.0, 0.1),
                             np.arange(10.0, 18.0, 0.5),
                             np.arange(18.0, 36.0, 1.0),
                             np.arange(40.0, 55.0, 5.0))) * u.mm
docs: Return array of possible drill diameters in metric.