I've got the milling machine showing up "soon" (Russian "soon" is more of a Southern minute than a New York one). Anyway, have to get the trolley done for the hoist so I can lift the base to our loading dock, then lift the mill onto the base.
Attachment 42067
Turns out one tap is undersized! Bit of a panic. Then I tried the other tap and it's the right size. So, I've started tapping in two steps, the undersized one and the correct one. Easier cutting deep threads that way.
Both taps are marked the same, so it's not like this was intentional.