Steel-Pinned Print-In-Place Knuckle Link
A two-link knuckle joint that prints already assembled: a 12 mm tongue turns on a 10 mm printed pin between clevis cheeks, with 0.5 mm clearance all round. The pin has a 4.1 mm bore, so you can push a 4 mm steel dowel through it for extra stiffness. Each 24 x 8 mm arm has four M3 clearance holes on a 10 x 12 mm pattern for bolting to robot arms, legs or linkages, and the tongue's fillet acts as a hard stop when the link is straight.
robotics joints print-in-place knuckle