In 1964 Sigma introduced and patented the first 4 prong Tee Nut with the now familiar 8-sided base. Unlike the standard round base, the new Sigma T-Nuts could be fed efficiently and reliably by machine. The 8-sided T-Nut base has become the standard configuration for T-Nuts inserted by machine. Sigma Tool & Machine is one of the world's largest T-nut manufacturers and suppliers for the upholstered furniture industry.
Today Sigma manufactures and supplies machine driven insertion Tee Nuts in the popular ultragrip style as well as the step barrel. Sigma sells T-nuts in a wide variety of sizes, options and finishes