This No.6–UNC (13/16) RH HSS split die is an adjustable external thread cutting tool intended for forming or repairing 1/4" class UNC fine/coarse (No.6) right‑hand threads on rods, studs and bolts. The split design allows a controlled closure or opening of the die to obtain a close or free running fit, making it suitable for thread restoration, workshop maintenance and small‑batch production where precise thread fit is required.

The die is manufactured from M2 high speed steel (HSS) and is supplied with a machined working face and a protective black oxide finish to reduce surface corrosion and ease chip evacuation. The thread form is Unified National Coarse (UNC) in accordance with ANSI/ASME B1.1 and the tool is produced to typical industry tolerances for interchangeability with standard imperial fasteners. This is a right‑hand external thread die (RH) intended for use in a split die holder or appropriate machine die stock; there is no head or drive profile as found on powered taps, the die is secured by the holder’s clamping screws.

The split die is designed with entry chamfers to start threads cleanly and with full cutting flutes for chip clearance. M2 HSS gives significant wear resistance and hot hardness compared with carbon steel dies, allowing reliable cutting of mild and medium carbon steels, aluminium, brass and many stainless steels in typical repair and workshop situations. For hardened materials beyond recommended limits consider ground HSS or carbide tooling.

Typical applications include maintenance and repair engineering, automotive and motorcycle rethreading, electrical and instrumentation assembly, marine refit where imperial threads are retained, and general engineering where UNC threaded components are used. Key benefits are the adjustability of the split die for achieving a desired running fit, the durability and temperature resistance of M2 HSS, and compatibility with standard UNC fasteners for interchangeability.

Duchy Fasteners stocks a wide range of imperial and metric dies and taps including individual split dies and complete sets. This No.6–UNC split die is available as a single item and in boxed options; please contact us for pack quantities and complementary die holders.