Knob for 3/8"-20 UNC camera mount bolt

Warning: requires lathe work to make a metal washer which is 2mm thick overall, has a 9.5mm central hole and a stepped external diameter. One step diameter is 19mm x 1mm thick and the other is 21mm x 1mm thick.

The bolt is a standard 3/8"-16 UNC that is used on larger cameras and telescopes. The ordinary camera bolt (Canon, Nikon, etc is the smaller 1/4"-20 UNC).

Camera knobs (even a cheap-o Desmond D-ring) goes for $6+. Other brand name levers, locks and knobs are very expensive. This on