Since nothing is ever easy

I was completing the repacking of rudder stuffing boxes this weekend which had to include replacement of the 1/2" BRASS studs due to some knucklehead using stainless nuts which resulted in corrosion that wouldn't allow the nuts to move. Cut three of the four in half fairly easily but the last one always has to be the worst. The stud would NOT spin out of the stuffing box by any means, even sprayed with PB Blaster and put heat to it. After two hours of attempts the brass stud finally gave in and snapped clean. GREAT!! Having so much room to work with and the majority of tools 2.5 hours away I bought a flexible shaft to fit the drill and some bolt extractor's. Got up to a 1/4" hole drilled in the bolt and started using the extractor's, one by one up to the largest size when .......the tip snapped inside the broken bolt, oh for f*$#'s sake. Back to store to purchase a second Dremel tool with flexible shaft and tungsten bit. 1.5 hours later all the extractor was ground out as was the majority of the brass bolt. I will return to the boat Friday with my 1/2" tap in hand to hopefully complete the task. Any suggestions on ensuring I get the tap straight, that is my biggest fear

You might fabricate a thick U-shaped plate from aluminum, steel, Starboard, or hardwood dimensioned so that the U fits around the rudder shaft. On one side drill a straight hole (via drill press) to fit over the good stud (or use a temporary bolt) to hold the plate in place. Locate a second hole sized to the OD of the tap. If the plate is thick enough it will guide the tap. You should be able to place the gland upside down on the plate to accurately locate the holes and the U. If you can't remove the gland because you can't remove the components above the rudder make a template with card stock or gasket material. Use the round side of a small ball-peen hammer to mark the positions of the holes in the gland.