Drilling a hole in a frame without internal dropper post cable routing is not recommended and will definitely void any warranties on your frame. It may also compromise the structural integrity of the frame, which could cause serious injury. If you have a frame without internal routing, purchase a post with external cable routing. Externally routed droppers are less common, but there are several models on the market to fit bikes without internal dropper routing. On some hardtail frames, you MAY be able to route cable housing through the seat tube water bottle mounts, but this can be quite tricky.