Many PCB Layout tools still output their Gerber drill layers built upon multiple Dcode vectors managed to get the round holes placed on the layer. While using Dcode vectors is fine for the Gerber files, it's useless for getting the Excellon drill tape.
FAB 3000 can convert the Dcode vector data to NC Drill, and it just requires a few steps.
- Import the Gerber file (which has the Dcode vector data).
- Select all Drill holes, and use the command menu: Tools / Draw to Flash / Selective (or Automatic). Choose "Circle" for the Shape for new flashes, review the other settings, and press OK. FAB 3000 will now convert those to simple flashes that can be easily output to Drill.
- Use the command menu: Fabrication / Drill / Gerber Layer to Drill...
- Export your Drill layer, menu: File / Export / Drill..
Here's a specific movie tutorial showing exactly how to perform the task,