WOW . I wonder just how we ever built guns without all the modern machining abilities ?
Less we forget , much of it was done with files , hand mills , hand drills , clams and bench vices .
Just saying .
Myself . I believe the gunsmith you took it to just didn’t want to mess with it .
Using a dental drill was mentioned . I would agree with that . You can also get very small , slow speed diamond drills . Harbor freight sells a set . They however are very cheep and if your not careful will snap .
Drill out the center as Doc stated . Then step up in bit size . How big of bit you can go , depends on how centered your first hole is .
The gun smith you took it to should have had small taps down to 1/16 at least .
You can get even smaller taps that are for watch making .
Tap the hole and pull the pin .