I need to drill and tap a 3/4-24 hole in an Indian transmission cover for the filler hole used on the '52&53 Chiefs. I am thinking that without some sort of fixture or guide, the tap will just ream out the hole rather than cutting threads. It is a plug tap, which is all I could find. I plan on starting from a hole reamed with a .71" dia reamer. Right now, I have the cover bolted to a steel plate and held in a mill vise on my Bridgeport. I have so far drilled the boss to 1/2" and will go to 45/64 then use the reamer. I am thinking that I can use my drill press to tap the hole, by turning the spindle by hand and feeding the tap with the down feed crank. Comments?