So your taking the star nut out, how do you intend to fit the fork? The star nut indicates that you have a threadless steerer, take it you are cutting down the steerer and threading it so you can use a quill stem?
If so, why bother to remove the star nut, as the cut for the threaded area will be several cm below the current position of the star nut
On top of the 'why' comments, plenty of steerers are internally butted, so knocking through the bottom won't always work. If you can't drill out out for whatever reason, if you have a long enough flat blade screwdriver you can insert it through the bottom of the steerer, and using a hammer, hit the underside of the SFN to fold the tabs upwards.
I thought that quill stems gripped the inside of the steerer tube by pushing out when they were tightened. Did I get that wrong? Or have I missed something?