The round thread is a knuckle thread, shaped to ensure it is not susceptible to dirt to ensure low maintenance. Common applications: Coupler shafts on railway vehicles, brake rods, respirators.
Knuckle thread screw taps are suitable for materials will good machinability up to 900 N/mm², non-alloy and low-allow steels, and for through and blind holes.
VOELKEL Thread-cutting tools
V-COIL Thread Repair System