I was about to replace my tv cable but alas the bolt head snapped off. I was thinking of using a flexible extension with a 90 degree as well to drill and tap. Just putting this out to see if anyone has any ideas to try as well in case my idea fails. Also, if anyone else has done this what size did you go up to for the bolt?

Thanks-Josh

 

Bummer on the broken bolt. Your idea is solid. A right-angle drill attachment is your best friend here.
Start with a small center punch to keep the bit from walking. Go slow and use lots of lube. I'd try a M6x1.0 tap if there's enough meat left. If it's really boogered up, you might have to go to a M7 (harder to find) or a standard 1/4" bolt and just snug it down good without going crazy on torque.