Edge and face withdrawal strength of large screws in particleboard and medium density fiberboard

Tests were carried out to determine the holding strength of large diameter sheet metal screws in the face and edge surfaces of medium density fiberboard (MDF) and particleboard. Additional purposes of the test were to determine the minimum acceptable length and width of specimens for edge withdrawal tests as a function of screw size and pilot hole diameter and also to determine the “zone of interaction” of one screw with another. Results indicated that the use of pilot holes of the proper diameter significantly increases the holding strength of the screws in the material. In general, pilot holes should be equal to about 80 to 85 percent of the root diameter of the screw. Results also indicated that edge withdrawal test specimens should be at least 4 inches deep by 6 inches long for screws embedded 1-inch deep (parallel to the 4-in. dimension of the specimen) for the screws to obtain maximum holding strength. Analyses of edge screw holding strength as a function of specimen length indicated that, in general, the zone of interaction is about 3 inches on each side of a screw for screws embedded in MDF and about 2.5 inches for particleboard.

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