It depends on the tap you have, but in my experience you will need to cut the tap. Just keep in mind that NPT is a tapered thread. Best to find a short bottoming tap. It also depends on where you're tapping/what box you have, if you use the endcover for pressure then it probably won't matter.
I've done it both ways, but if you're confident you can do it and have the time...pull it apart while you're at it. Just read up first.
