A circular internal bond test for predicting the holding strength of furniture fasteners

A circular internal bond (CIB) test was devised that provides a simple procedure for obtaining internal bond (IB) strength data that could be used as an indicator of fastener-holding strength. The procedure consists of drilling a hole two-thirds of the way through one face of a panel with a hole saw, and then drilling a concurrent hole two-thirds of the way through the panel from the opposite face with a hole saw of a smaller diameter. The method of the test consists of applying a load perpendicular to the face of the smaller of the two disks cut into the face of the board until the ring of material holding the disk in place fails. CIB strength is computed as the ultimate load divided by the difference in area of the two rings cut into the faces of the board. This method of test yields IB strength values that are only about two-thirds as great as those obtained by means of the conventional IB test method. Thus, the CIB tests cannot be substituted on a one-on-one basis for the standard American Society for Testing and materials IB test. Values obtained with the CIB test proved to be slightly better predictors of screw-holding strength than did those obtained by the standard method, however, If this relationship also holds true for other fasteners, the CIB test would provide a simple test method for obtaining board property data, which should prove useful both for quality control and for product design.

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