FINISHLINE

Happy Monday🤪
70 Cutlass Convertible. Inside RV mirror (the mirror itself not the support) won't tighten up. Mirror is also a little beat up so I dont mind replacing it. Found the parts on line but before I going spending $$$ is the mirror likely the "worn" part? Or should I invest in a new support as well? Also clearly not the original set screw in there. Was thinking maybe that screw just wasn't reaching far enough is a possibility or are these mirror parts being worn a common issue?
Thanks

Fun71

Are you meaning the screw with the yellow arrows? If so, not being the original screw may be the issue, ar at least part of the issue. As you can see in the left picture, the screw has a bevel so it tightens into the bevel in the clamp properly.
I have had issues with that screw in the past. If I remember, I had to get a slightly longer screw so it engaged more threads on the opposite side of the clamp because someone (I ain't naming any names) overtightened it and stripped the threads in the clamp.

FINISHLINE

HA!!!
Yes THAT screw . Mine is some weird torx screw someone before me threw in there. That original style screw is available from Fusick but I wasn't sure if 52 years of use hadn't actually worn the metal down either on the mirror or the mount? Does this happen or am I simply needing the correct screw? Little bit different style on mine as well. Pics below.

Fun71

The different style is convertible vs hardtop. I didn't search for convertible specific pictures.

You may be able to get that beveled screw at the local hardware store. If you get one too long, you can file the end down to get the right length (extra length, I should say).