This product is a 5/16" UNF (1") right-hand split die used to cut, restore or chase external Unified Fine (UNF) threads on bars, bolts and studs. It is intended for use with a compatible round die stock (die holder) and is designed to produce 5/16" diameter threads at 24 threads per inch (5/16"-24 UNF) suitable for common imperial fine-thread fastenings.

The die is manufactured from M2 high speed steel (HSS) for elevated hardness and wear resistance during cutting operations, and is supplied with a protective finish to inhibit corrosion between uses. As a split die it features a machined axial slot and an adjustment screw that allows slight tightening or opening to control thread fit and to compensate for wear. The thread form conforms to the Unified Inch system and is produced to the UNF profile as defined by ANSI/ASME B1.1, making it compatible with standard UNF fasteners and typical Class 2A fits encountered in maintenance and repair work.

Typical applications include automotive thread repairs and restorations, plant and machinery maintenance, engineering workshops, prototyping and vintage vehicle restoration where imperial fine threads are required. The split design makes this die particularly useful for chasing damaged or corroded threads and for cutting threads on undersized rods or turned components where a controlled fit is important. Operators should use an appropriate cutting lubricant and a die stock for safe, accurate cutting; M2 HSS will cut common steels and many alloy materials, though stainless steels may require slower speeds and suitable coolant.

Key benefits of the 5/16" UNF HSS split die include the wear resistance and regrindability of M2 HSS, the ability to fine-adjust thread engagement via the split/locking screw, and compatibility with the Unified thread standard for interchangeability with imperial fasteners. The protective finish helps resist corrosion in storage and service, and the die’s nominal 1" length provides good engagement for accurate thread form.

Duchy Fasteners holds a broad range of imperial dies and die sets in stock. This item is available individually and as part of assorted sets; we also supply matching die stocks and holders. Contact us for available sizes, pack options and same‑day dispatch from our Cornwall warehouse.