Need a jam bolt? An adjustment screw? Here's a simple knob handle for 3/8" bolts. The head should fit in the top and the insert slips over the bolt. Could be glued but press fits pretty well too. It's designed for a standard bolt.
8_Bolt_Knob_Insert.STL | 40.9KB | |
8_Bolt_Knob_Main.STL | 505.6KB |