Prevention of slug pulling in stamping presses

A punch and die assembly for punching a hole in stock material with the resulting production of a slug, the assembly comprising a die plate having a facial surface which is opposed to the punch, a die opening which extends from the facial surface through the die plate, the punch having a leading end portion and a leading end surface, the punch having a cross-section which conforms to the cross-section of the die opening, the punch being reciprocable towards and away from the facial surface between a retracted position and an extended position, the leading end surface being spaced from the facial surface when the punch is in its retracted position and extending into the die opening when the punch is in its extended position, the punch and die assembly being characterized in that:

• the die opening has an axis and an internal wall, the die opening being tapered so that the internal wall extends divergently from the facial surface, a camming rib is provided on the internal wall and extends inwardly from the facial surface along the internal wall, the camming rib extending obliquely along the internal wall relative to the axis of the die opening, the camming rib being engageable with an edge portion of the slug produced in a punching operation as the slug is pushed by the punch into the die opening and is effective to move the slug laterally in its own plane across the leading end surface of the punch whereby,
• when the punch returns to its retracted position, the slug is separated from, and does not adhere to, the leading end surface of the punch.