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It is said that the ordinary punch shears the panel in piercing. However, the best way to describe the piercing a hole with a breaking punch is that it occurs with a tear of the panel. Holes pierced with a regular punch cause clack to occur from both the front and rear end of the panel which originate from both the end of the punch blade and the button die end. The panel is then blasted when connected to the clack. Thus, in order to join the clack on both the front and rear of the panel in an appropriate manner, there was a need to make the clearance between the punch and the button die extremely small (0.03mm to 0.05mm). However, by making the edge (shoulder) of the breaking punch into an R-form, no clack occurs from the punch-side of the panel and occurs only on the button die side. From the time when clack occurs to until it has made it to the panel surface, hole opening is performed by pulling (tearing). The opening of holes with a breaking punch depends only on the button die edge. There is no need to adjust the connection of clack of the panel front and back as seen in regular punching. This makes possible the securing of a large amount of clearance (0.4mm to 1.5mm) in the area between the punch and the button die. This also allows eccentricity of the punch (up to 0.2mm). ■Hole-opening mechanism by Breaking Profile of breaking punch ・Sharp point at the end of punch. ・At the end of the punch (shoulder) there is round chamfering on the punch edge. R Shoulder Eccentricity amount is 0.01 to 0.02 Eccentricity is up to 0.2mm Clearance Clearance Projection tip Ordinary Punch Ordinary Punch Breaking Punch (Diagram) End point formation of breaking punch Differences in Fundamentals for Hole Opening of the Regular Punch and Breaking Punch Methods Breaking Punch Clack Clack Punch Clearance Small Large Eccentricity of the punch and button die Hole Adjustment Difficult Easy (unnecessary) Button Die Punch Button Die to Breaking punch Breaking Punch Punch Unit 391