| Compound dies combine two or more | | | | punches are employed. The metal sheet is moved |
| operations at one station as illustrated, strip stock is | | | | incrementally through the press each time the |
| fed to the die, two holes are punched , and the | | | | punches are withdrawn. The punched holes may be |
| piece is blanked on each stroke of the ram. when the | | | | almost any shape. All nonbrittle metals can be |
| operations are not similar, as in the case of a blanking | | | | perforated. |
| and forming operation, dies of this type are | | | | Misalignment of punch and die causes excessive |
| frequently know as combination dies. | | | | pressures, shearing or chipping ofdie edges, or actual |
| A progressive die set performs two or | | | | breaking of the tools, Such action may occur through |
| more operations simultaneously but at different | | | | shifting even though the setup is originally correct. To |
| stations. A punch-and-die set of this type is shown in | | | | prevent these occurrences, proper alignment is |
| Fig.17-2. As the strip enters the die, the small square | | | | ensured by guide rods at two or four corners of the |
| hole is punched. The stock is then advanced to the | | | | die that fit into holes in the punch holders, These dies |
| next station, where it is positioned by the pilot as the | | | | are known as pillar dies. This arrangement of having |
| blanking punch descends to complete the part. | | | | the punch and die held in proper alignment facilitates |
| This general type of design is simpler than the | | | | the setting up of the tools. A similar arrangement, |
| compound dies, because the respective operations | | | | Known as a subpress die and accasionally used on |
| are not crowded together. Regardless of the number | | | | small work, employs a punch and die mounted in a |
| of operations to be performed, the finished part is | | | | small frame so that accurate alignment is always |
| not separated from the strip until the last operation. | | | | maintained. pressure is applied by a plunger tat |
| In the perforation of metal one or two rows of | | | | extends out of the top of the assembly. |