PUNCH FOR THIN-PLATE METAL AND PUNCH DEVICE FOR THIN-PLATE METAL WITH THE PUNCH

摘要

A punch (13) for thin-plate metal (8) has a punch body (25) and a cone-like projection (28). The cone-like projection (28) is integrally joined, at its bottom surface, with one end surface of the punch body. The bottom surface has a circular shape whose center is concentric with the center of an imaginary circle with which the outer edge of the one end surface is in internally contact and has the outer edge in internally contact with an imaginary circle having a smaller diameter than the imaginary circle with which the circular shape is concentric. An angle (theta) formed by a line that intersects the axis passing through the center of the imaginary circle with which the outer edge of the one end surface is in contact and is tangential to a tip-end surface of the projection and by the one end surface is not less than 25º and not more than 60º. Further, the ratio e/L is set not less than 0.05 and not more than 0.14, where (e) is the difference between the radius (D1)/2 of the imaginary circle with which the outer edge of the one end surface is in internally contact and the radius (d1)/2 of the imaginary circle with which the outer edge of the bottom surface is in internally contact, and (L) is the circumferential length of the imaginary circle with which the outer edge of the one end surface is in internally contact.