A steel rule die is a simple yet effective die-cutting device used to cut, perforate, or score a variety of materials. The dies are made by cutting a thin slot into a flat, rigid base such as wood laminate which mirrors the shape of the end product. A thin steel strip is pushed into the slot so that it protrudes above the base to a height dictated by the desired thickness of the end product. The edge of the protruding steel strip may either be sharpened along the entire edge if a clean cut-out is required, intermittently sharpened if a perforated cut is required, or rounded in various profiles if the material is only to be scored. The complete die is then placed into a press that contains the cut-out material and is pressed down onto it to complete the die cut cycle.
Die cutting is a process where a shaped cutting device is pressed into a sheet of material to cut out its shape from that material. A simple cookie cutter is an excellent example of this process, and an equally good example of how one of the more popular types of die cutter — the steel rule die — works. The cookie cutter consists of a thin plastic or stainless steel tube formed into a decorative shape. When the cutter is pressed into a sheet of dough, that shape is cut from the sheet. A steel rule die works in exactly the same way to cut shapes from a variety of materials, including rubber, vinyl, and paper.
To build a steel rule die, a flat sheet of robust substrate, such as wood laminate or aluminum, is cut with a thin slot in the shape of the finished product. The slot is typically between 0.028 and 0.056 of an inch (0.7 and 1.4 mm) wide and is usually cut with a laser cutter. A thin, highly-flexible steel strip is then laid into the slot along its entire length. The strip, or rule, is high enough to sit on the bottom of the slot with a certain amount of its body clear of the surface of the substrate, forming what would be the “tube” of the cookie cutter. Due to the flexibility of the rule, these dies may be made to cut extremely complex shapes.
The upper edge of the rule is equipped with a variety of finishes depending on the intended purpose of the cutter. If a clean cut is desired, the upper edge is sharpened with a variety of profiles depending on the material that it will cut. If a perforated cut is required, the rule edge will be equipped with an intermittent cutting edge of a suitable pitch. Scoring dies are simply rounded to make an impression in the surface without cutting through it. To make the cut, the steel rule die is placed in a press that forces it down onto the sheet of material, cutting or scoring the desired shape in the process.