A thread-cutting die head includes a die carrier supporting thread-cutting dies for displacement in a radial direction, a cam plate coaxial with the die carrier including a plurality of cam members for engaging the thread-cutting dies and displacing the cutting dies in a radial direction in response to relative rotation between the cam plate and the die carrier, and a locking system. The locking system includes a positioning screw extending through an arcuate slot in the cam plate, a cam washer surrounding the positioning screw, and a pin threaded to the positioning screw. The locking system further includes a cam handle including a cylindrical cam portion engaged with the cam washer. Rotation of the cam handle in a first direction is configured to impart a clamping force against the cam washer to lock the rotational position of the cam plate relative to the die carrier.

A thread-cutting die head includes a die carrier supporting thread-cutting dies, a cam plate coaxial with the die carrier including cam members displacing the cutting dies in a radial direction in response to relative rotation between the cam plate and the die carrier, and a locking system. The locking system includes a bushing, a die-locking arm pivotably supported upon the bushing, a positioning screw extending through an arcuate slot in the cam plate and the die-locking arm, the bushing threaded to the positioning screw, and a coupler coupled for co-rotation with the bushing and engaged with the die-locking arm when the coupler is in a first position, in which rotation of the die-locking arm in a first direction rotates the bushing in a tightening direction, imparting a clamping force between the bushing and the cam plate to lock the rotational position of the cam plate relative to the die carrier.