Grab handle stumps

Underneath the grab handle at the sides of the bike, it seems there should be a metal stud or stumpy thing, presumably for tie down hooks. On my bike these have snapped off, or been replaced by something else for the luggage racks, which i have removed. So before I repaint the grab handle I tried drilling out the remains so I have the internal thread to use in future. But, whatever is in there is made from really tough hardened steel and after 3 hours i`m still not getting very far.

How deep does the original threads go in to the handle ? If its likely to be quite deep i`ll just give up and fill over the recesses and forget it.

Edit: Doesn`t matter, i`m gonna fill them in.