components require thousands of dies. So do streamlined trains, aircraft, and missiles. All of these are improved from year to year, so an enormous number of new dies is constantly required.
The foregoing should give you some idea of the great size and importance of the pressed-metal industry.
Figure 1.7 A typical punch press.
1.1.8 Punch Press
Figure 1.7 is a photograph of a typical mechanical punch press in which dies are operated to produce stampings. The bolster plate A is a thick steel plate fastened to the press frame. The complete die is clamped securely on this bolster plate. The upper portion of the die is clamped in ram B, which is reciprocated up and down by a crank. As the material strip is run through the die, the upper punches, which are fastened to the moving ram B of the press, remove blanks from it.
Figure 1.8 is an exploded drawing of the die shown in Figure 1.5 with the names of various die components listed. These names should be memorized because we will refer to them many times in future work.
Figure 1.8 An exploded view of the die shown in Figure 1.5.
Figure 1.9 A typical die set.
1.2.1 Die Set
Figure 1.9 shows a die set, and all parts the die assembly comprises are built within it. Die sets are made by several manufacturers and they may be purchased in a great variety of shapes and sizes. The “center posts” A are called “punch shanks” in the die set manufacturers’ jargon. And, no, they cannot be used for clamping the punch holder, but they can be used for aligning the die in the press. Ram mounting holes must be provided in the punch holder for mounting. In operation, the upper part of the die set B, called the “punch holder,” moves up and down with the ram. Bushings C, pressed into the punch holder, slide on guide posts D to maintain precise alignment of cutting members of the die. The die holder E is clamped to the bolster plate of the press by bolts passing through slots F.
In Figure 1.10, the die set is drawn in four views. The lower left view shows a section through the entire die set. The side view, lower right, is a sectional view also, with a portion of the die set cut away to show internal holes more clearly. The upper left view is a plan view of the lower die holder with the punch holder removed from it.
The punch holder is shown at the upper right, and it is drawn inverted, or turned over, much like an opened book. In the complete die drawing, Figure 1.2, all punches are drawn with solid lines. If the punch holder were not inverted, most lines representing punches would be hidden and the drawing would contain a confusing maze of dotted lines.
Figure 1.10 A die set.
Another reason for inverting the punch holder is that this is actually the position assumed by the die holders and punch holders on the bench as the die makers assemble the die, and it is easier for die makers to read the drawing when the views have been drawn in the same position as the die on which they perform assembly motions.
1.2.2 The Die Block
Figure 1.11 shows the die block of the die shown in Figure 1.2. The die block is made of hardened tool steel into which holes have been machined, before hardening, at the piercing station and also at the blanking station. These are the same size and shape as the blank holes and contour. Other holes are tapped holes used to fasten the die block to the die holder, and reamed holes into which dowels are pressed to fix the block’s location relative to other die parts.
Figure 1.11 The die block.
The top view is a plan view of the die block. The lower left view is a section through the holes machined for piercing and blanking. Lines drawn at a 45-degree angle, called “section lines,” indicate that the die block has been cut through the center, the lines representing the cut portion. Similarly, the end view is a section cut through the die block at the blanking station. A tapped hole is shown at the left and a reamed hole at the right side. These are for the screws and dowels that hold the die block to other die components. Sectioning a die, that is, showing the die as if portions were cut away to reveal the inside contours of die openings, is a very common practice. In fact, practically all dies are sectioned in this manner. The die maker can then “read” the drawing far more easily than he could if outside views only were shown because these would contain many dotted or hidden lines.
Always remember that all drafting is, in a sense, a language. A die drawing is a sort of shorthand, which is used to convey a great deal of information to the die makers. Anything that can be done to make it easier for them to read the drawing will save considerable time in the shop.
Now refer back to Figure 1.2 and see how easily you can pick out the three views of the die block. That is exactly what the die maker has to do in order to make the die block.
1.2.3 The Blanking Punch
The blanking punch (Figure 1.12) removes the blank from the strip. The bottom, or cutting edge, is the shape and size of the part. A flange at the top provides metal for fastening the blanking punch to the punch holder of the die set with screws and dowels. Two holes are reamed all the way through the blanking punch for retaining the pilots, which locate the strip prior to the blanking operation. Locate the views of the blanking punch in the die drawing, Figure 1.2, to improve your ability to read a die drawing.
1.2.4 Piercing Punch
A piercing punch (Figure 1.13) pierces holes through the material strip or blank. It is usually round and provided with a shoulder to keep it in the punch plate. When a piercing punch penetrates the strip, the material clings very tightly around it. A way must be provided to strip or remove this material from around the punches. The means employed to remove such material is called a “stripper.”
Figure 1.12 The blanking punch.
