Plus from the picture, it looks like one of those cast malleable iron plumbing/steam fittings so can't be taken as square or parallel.
Doesn't look like there is much to chuck it by, so you start by making a mandrel or split collar ... oh yeah, you don't have a lathe. Its a nice little job if you are just playing and paying yourself. Someone else "on the clock" will cost proportionally more.
A new decent tap @around $20, and you still have the problem of how to fixture it.
Perhaps you could get a thread compatible "tee" which you could use in a machine vice? Especially if you could mill the sides flat so it would be standing properly vertical. Then as mentioned use your drill press for preference, but if you hold it securely, you may find a hand job is acceptable.
You don't say what it is for, maybe neerenuffisgudenuff?