I been working on my sport mirror and just removed the broken knob and then ordered one from e-bay for a mustang with threads. While waiting for the part to arrive and went to my 73' 4door maverick and realized it had a broken chrome mirror but a good knob so, I took it off and put the base in a vise and decided to use some heat from my torch and then use vise grips to turn knob, Thats not what happen the part holding the knob just melted away and the knob just fell out on to the floor to my supprise unharmed, because the knob is made out of some harder metal than the base. Then i cleaned the knob at the tip and tapped it in the sport mirror base. I would only recommend this on a old broken mirror that you do dont care about or going to use other than parts. I hope this helps someone.
