I have not followed your previous posts so I do not know what type of machine you converted but I can give you a little information on tapping with the old Bridgeport style mills without a tapping head. This only works if you can release the spindle and feed it by hand. You will probably find a tapping head to be a good investment however.

Spot and drill the holes with the CNC capabilities. Now you can manually return to the exact position of each hole or write a code for each spot/drill operation and the machine will be there. Put the tapered tap in the chuck and manually crank the spindle down to the point where the tap contacts the hole. While maintaining moderate downward pressure on the spindle/quill rotate the chuck by hand to start the tap into the hole. You only need a couple of revolutions to get it started straight. Loosen the chuck key and pull the spindle/quill up and away from the hole leaving the tap protruding from the hole. Now put a regular hand taping handle on the tap and finish the job by hand. The secret to tapping has always been starting the tap straight and this will accomplish that. You will probably want to finish the bottom of the holes with a bottoming tap.

This process also works with the tail stock on a manual lathe. If your lathe will turn slow enough, less than 100 rpm, you can set the tail stock to slide but not move around and turn on the lathe which will draw the tap into the work. Remember, there will be some lag from where you turn off the motor and when the chuck stops rotating I doubt if either of these procedures are OSHA approved so proceed at your own risk.

Vern