How deep do you need to go for npt taps? Sink it down or just the top?

How deep do you need to go for npt taps? Sink it down or just the top?

Leave maybe half a dozen turns showing on the tap then back it out and try threading in the male (or second tap if you have a set). Don't forget to back it up to break the chip and it looks like you're being stingy with the lube.