In 1964 Sigma introduced and patented the first 4 prong T-Nut with the now familiar 8-sided base. Unlike the standard round base T-Nuts, 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 manufacturers and suppliers of T-Nuts for the upholstered furniture industry.
Today Sigma continues to manufacture and supply quality T-Nuts designed for machine insertion. Machine driven T-Nuts are available in the popular ultragrip style as well as step barrel T-Nuts in a variety of sizes, options and finishes