| 摘要 |
<p>To permit punching of very small holes from a strip of sheet metal, for example to form a sequence of holes at the margin thereof, or to obtain small punched blanks, having diameters of a few millimeters, for example 1-2 mm or even less, and prevent adhesion of the punched blanks to a reciprocating punch plunger (1), the punch die (4) is formed with a shallow groove (8) in the wall of the opening (5) of a die, the groove extending either spirally or axially for the depth of penetration or stroke of the punch plunger. Upon withdrawal of the plunger, a small projection or nose which will have formed in the region of the groove will wedge or jam therein, thus preventing upward travel of the blank with the withdrawing reciprocating tool. Preferably, the opening is slightly conical, with a cone angle of, for example, about 1/2 DEG with respect to the axis (12) of the bore (5); a suitable angle of inclination for a spiral groove is, for example, 12 DEG , and a suitable plunger penetration, for example with a straight, axially extending groove, is about 1 mm.</p> |
