The DIN EN 22568 HSS-G left-hand circular dies for metric threads are designed for producing external left-hand ISO metric threads according to DIN 13 on rods, pins, studs, special screws, mechanical components and parts that need to be manufactured, reworked or repaired. Unlike standard right-hand threads, left-hand threads tighten counter-clockwise and are used in applications where rotation, vibration or the operating direction of the component could loosen a conventional right-hand thread. They are therefore particularly suitable for rotating parts, adjustment systems, special mechanical assemblies, industrial maintenance, technical spare parts and components subjected to operating directions opposite to standard tightening.

The HSS-G high-speed steel construction provides good wear resistance, stable thread profile and accurate thread formation. The 60° thread profile, 6g tolerance and closed pre-slotted Form B geometry allow regular and controlled left-hand metric threads to be produced, maintaining good profile quality and stable guidance during feed into the workpiece. The closed Form B design is suitable when correct and progressive starting is required, while the pre-slotted construction helps distribute cutting forces and supports accurate thread formation. These dies are suitable for materials with tensile strength up to approximately 800 N/mm², including structural steels, unalloyed steels, free-cutting steels, mild steels and general metallic materials compatible with HSS-G cutting tools.

The correct version must be selected according to nominal thread size M, pitch, outside die diameter, die height and compatibility with the die holder being used. It is always important to verify that the application actually requires a left-hand thread, because the cutting direction and tightening direction are opposite to standard right-hand metric threads.

To obtain accurate threads, the external workpiece diameter must be prepared correctly, a suitable starting chamfer must be made, the die must be kept coaxial and perpendicular to the component axis, and appropriate cutting lubricant must be used. In left-hand threading, special attention must be paid to the tool rotation direction: feed occurs in the opposite direction compared with right-hand dies, so incorrect use can damage the entry chamfer, ruin the profile or compromise the thread. Incorrect workpiece diameter, misaligned starting, insufficient lubrication or unstable guidance can cause incomplete threads, torn thread profiles, increased cutting effort, premature die wear and difficult feeding.

During machining, progressive cutting with periodic chip breaking is recommended, especially on larger diameters or tougher materials. These dies are suitable for mechanical workshops, maintenance technicians, toolrooms, production departments, automotive work, mechanical engineering, industrial repairs and special applications where reliable, accurate left-hand metric threads are required for components subjected to rotation or non-standard tightening conditions.