Howard thanks for the advice – Ive tried both and given up and ordered a set of new circlip pliers .
The assumption that it is external is correct, but there is no reason why the holes should have been halved theres plenty of clearance.
The one Im trying to get off is holding the spindle assembly into the top bearing..
Removing it is the only way in to get to the gear and remove/replace it.
Why use a nylon gear at this point with the difficulty there is in replacing it is difficult to understand the motor gear is brass and the next gear is also nylon and far more accessible.
At least on the mini lathe the bottom of the headstock is open and access is reasonable.