SFIV1967
Venerated Member
The inner diameter of the ball ends should be 0.126" = 2,00 mm. A 2mm steel rod might not be strong enough holding the tension of the high e string since it is not supported on the end. Not sure, but at least something to try! It might bend over time and you lose tune.Meanwhile help - You coud stick a thin steel rod throught the ball-ends of other strings and have that E-string supported on that.
Ralf