In compound punching, the shape of the product (Fig. 1) and the shape of the compound punching punch (Fig. 2) appear identical to the eye.
The outline shape of the punch becomes the punch for outer shape punching. Relative to the dimensions of the outline of the product, the outline shape of the punch is prepared to be smaller by the clearance between them.
The holes inside the punch are the hole punching dies. They are made smaller by the amount of the clearance with respect to the hole dimensions of the product. The precautions about the drop hole for scrap are the same as in hole punching operations.
Since any scrap getting clogged can immediately cause breakage, the cutting edge of the die is made shorter. When there are several holes that are close to each other, the holes are combined into a single larger hole in the middle so as to make it into a drop hole for scrap and obtaining a structure in which scrap clogging does not occur easily.

If the drop hole for scrap is made wide in the case of small shapes, the thicknesses of the side walls become smaller causing the die to break easily. Hence, a countermeasure is taken such as providing a stepped shape as shown in Fig. 3. In the case of odd shaped punches, these are also prepared by chamfering machining or reverse electrical discharge machining. The thinking in this regard is determined according to the design of the punch.

A method of fixing the compound punch is to fix using screws by drilling and tapping holes in the punch if the shape is large.
When machined straight by wire electrical discharge machining, grooves are machined in the side walls by grinding, and fixing by keys is done using those grooves, or else, a part of the outer shape is wire-machined large, and that part is later ground to form a flange. The method of fixing the punch is the same as the method of fixing a blanking punch.
The material of the punch is commonly SDK11 heat treated to about 60HRC.