Fasteners for a lasting, firm hold

 

Fasteners for a lasting and firm hold

Your basic common screw isn't quite so common anymore. The ever-changing climate of tools, bits, and materials has led to an explosion of specialized designs. The greater use of dense hardwoods, the development of composite materials, and changes in preservative treatments also have exerted their influence.

To begin with, the density of composite materials creates problems of splitting, mushrooming (when material is pushed up and out around the screwhead), and screws "spinning out" (when threads lose their bite) before the heads are fully countersunk.

While better for the environment, the changeover from the old CCA wood treatment to the new ACQ treatment has proven to be far more corrosive on fasteners. Many experts recommend only stainless-steel or hot-dipped zinc fasteners for use with ACQ; however, many other screw types are billed as suitable for ACQ. Currently, the fastener industry is self-governed and sets its own standards for what constitutes an ACQ-rated screw for treated stock.