The Vardex Standard TM indexable thread milling system is the world's most popular indexable thread milling system. One tool holder can be used for machining metric, UNC, UNF, UNJ, BSPT, Whitworth, PG or NPT threads, simply by changing the insert. Taper thread mill inserts (NPT & BSPT) must be used in CONICAL toolholders. The Vardex Standard TM range has 6 series of inserts: 6mm, 1/4", 3/8", 3/8"B, 5/8" & 3/4"B (measured by the inscribed circle dimension of the insert I.C.). The larger the insert, the more teeth it will have and large pitch can be machined.