I need to drill conical holes that are narrow at the deep and and wider at the top into cylindrical bars. The measurements need to be very precise. I was thinking of using a narrow drill for the entire depth of the hole and a wider drill for the first 1-2mm, then sticking the piece into a lathe and try to make the taper to the best of my abilities with a few hand tools (round file, grinding stick).
I was thinking of using a narrow drill for the entire depth of the hole and a wider drill for the first 1-2mm
It'd probably be best to do the whole operation on the lathe. That'll ensure that the initial holes and subsequent work are all centered on the same spot. If you have access to a metal lathe, use that; it'll let you set the taper angle you want and reproduce it. If you only have a wood lathe, consider making a jig that mounts to the tool rest and guides a tool along the desired angle.