While there are many die-cutting operations, some of which are very complex, they can all be reduced to the following simple fundamentals.

Fig. 4-1 Drop-through Blanking Die Fig. 4-2 Piercing Die Assembly

4.1.1 Plain blanking: Fig. 4-1 shows a simple operation of this type. The material used is called the stock and is generally a ferrous or nonferrous strip. During the working stroke the punch goes through the material, and on the return stroke the material is lifted with the punch and is removed by the stripper plate. The stop pin is a gage for the operator. In practice, he feeds the stock by hand and locates the holes to be punched as shown. The part that is removed from the strip is always the work piece (blank) in a blanking operation.

A progressive die performs a series of fundamental sheet-metal operations at two or more stations during each press stroke in order to develop a workpiece as the strip stock moves through the die. This type of die is sometimes called cut-and-carry, follow, or gang die. Each working station performs one or more distinct die operations, but the strip must move from the first through each succeeding station to produce a complete part. One or more idle stations may be incorporated in the die, not to perform work on the metal but to locate the strip, to facilitate inter station strip travel, to provide maximum-size die sections, or to simplify their construction.
The linear travel of the strip stock at each press stroke is called the progression, advance, or pitch and is equal to the inter station distance.

The unwanted parts of the strip are cut out as it advances through the die, and one or more ribbons or tabs are left connected to each partially completed part to carry it though the stations of the die. Sometimes parts are made from individual blanks, neither a part of, nor connected to a strip; in such cases, mechanical fingers or other devices are employed for the station-to-station movement of the workpiece.

The operations performed in a progressive die could be done in individual dies as separate operations but would require individual feeding and positioning. In a progressive die, the part remains connected to the stock strip, which is fed through the die with automatic feeds and positioned by pilots with speed and accuracy.