Methods of Measuring Die-Cutting Shear Strength of Hardboard

The die-cutting shear strength of 1/8-, 1/4-, and 3/8-inch-thick standard and tempered hardboards were evaluated by both the Johnson double-shear tool and the ASTM D 732-46 shear test for plastics. Maximum shear stress was generally higher for the more dense products as well as for the more dense specimens from the same product. Variability of the individual specimen values was approximately the same for both test procedures. Maximum shear stress ranged from 2,300 pounds per square inch for one of the 3/8-inchthick boards to more than 4,500 pounds per square inch for the 1/8-inch-thick board. Both test procedures gave essentially the same value for all but one of the ten products evaluated. The difference between shear strength measured by the two methods was approximately 20 percent for the one material. This difference is most logically explained by differences in properties in the machine direction and cross-machine direction of the panel as manufactured. The use of the circular tool of ASTM D 732-46 is preferred because it averages directional differences.

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