Wiseman HSS UNC Left Hand Split Dies – Unified National Coarse Thread

Wiseman HSS UNC Left Hand Split Dies are manufactured from High Speed Steel (HSS) and designed for cutting new external UNC (Unified National Coarse) left-hand threads, as well as repairing, cleaning and restoring damaged or worn existing threads.

These round split dies feature an adjustable design, allowing minor adjustments to the thread fit when used with a suitable die stock. They are particularly useful for general engineering, machinery maintenance, specialist repairs and workshop applications requiring left-hand threaded components.

UNC threads feature a 60° Unified thread profile and a relatively coarse pitch compared with UNF (Unified National Fine) threads of the same nominal diameter. The coarser thread pitch makes UNC threads widely used in general engineering, machinery, equipment assembly and industrial applications.

Unlike standard right-hand threads, left-hand UNC threads tighten anticlockwise and loosen clockwise. They are commonly used in applications where the direction of rotation, mechanical movement or equipment design requires a reverse-threaded fastening.

These split dies are suitable for producing and restoring left-hand UNC threads on bolts, studs, rods, shafts and other externally threaded components.

Key Features

• High Speed Steel (HSS) – Durable construction for reliable thread cutting and maintenance.

• UNC Thread Form – Designed for Unified National Coarse external threads.

• Left Hand Thread – Tightens anticlockwise and loosens clockwise.

• Adjustable Split Design – Allows minor adjustment of the thread fit when used with a suitable die stock.

• Round Die Construction – Designed for use with compatible die stocks and die holders.

• 60° Thread Profile – Unified thread form with a coarse thread pitch.

• Thread Cutting & Restoration – Suitable for cutting new external threads and repairing existing threads.

• Reverse Thread Applications – Suitable for components requiring left-hand threaded fastenings.

• Engineering & Workshop Use – Suitable for general machining, fabrication and maintenance.

Applications

Suitable for:

• Cutting new UNC left-hand external threads on rods, bolts and studs.

• Repairing damaged or worn UNC left-hand threads.

• Cleaning and restoring existing external threads.

• Manufacturing left-hand threaded shafts and fasteners.

• Machinery and mechanical equipment maintenance.

• Rotating assemblies requiring reverse-threaded fastenings.

• Specialist automotive and industrial engineering applications.

• General engineering and workshop machining.

• Manufacturing replacement left-hand threaded components.

Recommended Use

Select the correct UNC left-hand split die diameter and threads per inch (TPI) to match the required external thread.

Secure the die in a compatible die stock or holder, ensuring the adjustment screws are correctly positioned. Prepare the workpiece to the appropriate diameter and apply a suitable chamfer to help the die start squarely.

Apply a suitable cutting lubricant and rotate the die anticlockwise to cut the left-hand thread, viewed from the starting end of the workpiece. Periodically reverse the die clockwise slightly to help break and clear chips where appropriate for the material and cutting conditions.

The adjustable split design allows minor adjustments to the thread fit. For accurate results, check the finished thread using a suitable UNC left-hand thread gauge or correctly specified mating component.

Ensure that the die is started squarely and that the correct cutting direction is maintained throughout the operation.

Important

• • Suitable for UNC (Unified National Coarse) left-hand external threads only.

  • Left-hand threads tighten anticlockwise and loosen clockwise.

  • Not suitable for cutting standard right-hand UNC threads.

  • Features a 60° Unified thread profile.

  • Not interchangeable with UNF, UNEF, metric, BSW or other thread forms.

  • Adjustable round split die for cutting and restoring external threads.

  • Requires a compatible die stock or die holder.

  • Ensure the correct nominal diameter and TPI are selected before use.