Gray window knob set screws..
I searched this site for a "how to" fix the loose gray window knobs. I found several references to some creative fixes involving threading the ends of the rods, etc, and a suggestion to thread the hole by user greghoro.
Using greghoro's suggestion about threading the hole.
Here's what I did, and what you need.
1/4"-20 set screws 1/4" long
Allen wrench to fit set screws
No drilling necessary, the 1/4"-20 tap will thread the hole quite nicely. If you wish to put a flat on the window rod, add a file (or Dremel tool) to the list. I did not put flats on the rods. The set screws seem to be holding well, and it stops the knobs from turning or coming off. You can tighten them securely, just be careful not to strip them out.