I thought all Hardinge turrets were self indexing, these were made for fast production (I could be wrong) so perhaps there are parts missing???

[edit - having seen your pictures] Oh yes, that looks like it just has a ball-bearing detent

The powerfeed is I believe just the motor, I have had a look in the control box and everything in there looks OK, biggest pot I have ever seen, didn't know they made that big
You probably want to hope that it's not the motor :( I doubt they are available from Hardinge for less than an arm & leg and second hand ones from HLV's are almost as rare as originals. Peter Coleman (Yahoo Hardinge group etc.) had to replace his with a three-phase motor (I don't think it was such a huge success)

The 'pot' is a variable transformer or 'variac' - it varies the voltage (rectified to DC) to the armature .

it looks like both solenoid & cork are buggered.
Check the solenoid continuity (it may be just a mechanical problem - It has happened to my HLV-H )