A self-opening diehead holds multiple cutting chasers that collapse radially outward at the end of a threading stroke, allowing the workpiece to be withdrawn without reversing the spindle. This eliminates the time-consuming back-off cycle required with solid dies, making self-opening dieheads the standard choice for high-production pipe and bolt threading lines.

At the SITC level, all tool holders for machine tools fall under 73511 regardless of the taper or interface standard. However, at the HTS 10-digit level, distinctions by type or material may apply, so importers should verify the precise subheading with a licensed customs broker, particularly for high-value precision holders that may also be subject to Section 301 tariffs depending on origin.