Elbow Axle Thrust Collar
A shaft collar for the 8 mm elbow rod in the 'NEMA17 Belt-Drive SCARA Drawing Arm' kit: 32 mm OD, 10 mm tall, with an 8.3 mm bore and a raised thrust ring (11 mm OD, 0.5 mm tall). The ring pushes up only on the inner race of the forearm's lower 608 bearing. It locks with one M3 set screw into an M3 nut that drops into a 5.7 mm slot open at the top. Two grip flats 29 mm apart let you hold it while you tighten.
robotics kit shaft-collar 8mm-rod