I did not have the luxury of a milling machine. I cut the threads in my block with a hand drill and hand tools. You need some serious leverage to turn a standard 1/2 inch pipe tap by hand. I agree you need a cut off tap to get the threads right in a shallow hole. You appear to have a machining background as do I. Glad to see you are handy.
Nice work. I always say that to be in this hobby, sometimes you have to improvise and use what you have available to you.
You have to Mcgiver it lol.