The 01-support part I created more for reference. If possible, make metal, steel or aluminum.
The hole should be threaded to M6.
The two rods with pin lock washer for the knurl wheel I made in the lathe, but you can use two 3/16 x 25mm screws.
(The knurl wheel I had here was a 16x8mm with 5.7mm hole. Unfortunately M6 bolt does not fit in the hole).
Glue the M5 bar on the Knob with cyanoacrylate.

You will also need:
2 Screws M6 x 25mm
2 M6 nuts
1 Screws M6 x 20mm
1 Threaded bar M5 x 80mm
1 Spring pressure 6 to 8mm internal diameter and 50mm length.
2 Washers (M5 or M6 depending on spring diameter)
2 screws 3/16 x 25mm.
2 Nuts 3/16 (Better if nyloc).

Best print with:
0.2 Layer
80% Infill
Use support only in Rod_1.stl

Update

Added Arm-threaded.stl to make thread in one of the holes and to dispense the M6 and 5/16 nuts.
It is possible to create the threads without using tap thread.
Simply grind the tip of a screw into an emery or even a file.
Lightly heating the tip of this new tool can help when making the thread.