Scroll Cam Three-Jaw Centering Clamp
A print-in-place scroll-chuck style fixture: turning the red cam ring drives three jaws in and out together, self-centering round work from 20 to 36 mm diameter (1/2", 3/4" and 1" schedule-40 PVC at 21.3 / 26.7 / 33.4 mm all fit) over a 20 mm through bore for drilling. 117 mm across, 24 mm tall, with three M3 clearance holes (3.4 mm) on a 104 mm circle to bolt it down to a bench or drill-press table.
tool workholding fixture jig