PURPOSE: To prevent the occurrence of abrasion of a cutting blade part and a bite of materials to be cut in the cutting blade part, and reduce die cost by obtaining the optimal clearance according to respective plate thicknesses when a lead of a fluorescent character display tube is formed while cutting the materials to be cut having different plate thickness by the same die.

CONSTITUTION: In a punch 3a, a step part J is arranged on a surface in a parallel direction with a cutting blade A. A dimension of this step part J is set in the same dimension with a difference in respective optimal clearances of two kinds of materials to be cut. Thereby, when a punch 3a installing direction is selected to be in a direction for turning inside out or for turning upside down, the optimal clearance according to respective plate thicknesses can be obtained. Thereby, abrasion of the cutting blade is reduced, and a bite in the materials to be cut is eliminated.