What is Unitized Tooling?

Typical functions, in addition to punching holes, include notching, forming radii on corners, edge-notching, edge-forming, lancing, and so on.

In addition to working with flat metal, plastic, and even glass, unitized tooling is widely used to punch or notch structural shapes such as channel iron or angle iron. It's also widely used to punch holes and notches in oddly shaped aluminum extrusions.

Tooling units

Examples of unitized tooling units appear below.

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Figure 1

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Figure 1 shows a typical unit. The top of the die is 3-1/2" (89 mm) above the bottom of the holder (this dimension is known as "die height"). When the press is in the normal down position, the top of the punch to the bottom of the holder is 8-3/8" (213 mm). (This dimension is known as "shut height.")

The unit is 1.5" (38-mm) wide and has an 8" (203-mm) throat. For this holder, the maximum round hole diameter is 5/8" (16 mm). Any shape can be made that fits within this 5/8" circle.

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Figure 2

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The unit shown in Fig. 2 is 8" (203-mm) wide and can work right alongside the narrower unit. It has self-contained stripping pressure able to lift a 5" (127-mm) punch out of 10-gauge mild steel, or a 3-1/2" (89-mm) punch out of quarter-inch (6.4-mm) mild steel. These large holders are available off the shelf with throat depths of 12-1/2" (318 mm) and 18-1/2" (470 mm).

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Figure 3

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Figure 3 shows several tooling units that were pre-assembled on a template outside the press, after which the template was set up in the press. The symmetrical punched part lends itself to a "hit-and-flip" operation, so the user could cut the number of tooling units in half if necessary. (With a hit-and-flip setup, the press hits the part once, the operator flips it, and the press hits the part again, creating a completed part.)

The figure also illustrates another common series of unitized tooling. Here, the stripper springs are recessed into the holders, so the shut-height can be a reduced 5-1/2" (140 mm). The die height is 2-19/32" (69 mm).

Alternative applications

Unitized tooling is also a solution for punching tubing, aluminum extrusions, and structural shapes. For example, a tube-pierce unit was developed for piercing countersunk holes in tubes used in lawn furniture.

The tube is supported on all sides during punching. The top hole on one side of the tube is distorted, which varies depending on the punch size; the bottom hole on the other side is punched into a die for minimal distortion. Other tube-pierce units punch tubing from both the top and bottom. Units may also be used with a mandrel for distortion-less punching.

--Henry C. Llop

Henry Llop is president of UniPunch Products Inc. (Buffalo, NY; hllop@unipunch.com). The above is an excerpt from a paper he presented at 2002 FABTECH.