A note on spring, I recently turned an 1.5-8 thread Gage and I probably made 3-5 spring passes after every compound adjustment because of the large course thread, at that size .001 is ALOT of stress and force.
One thing that may help you determine when your "there" is to cut a relief on the nose or the back of the thread that is the same as the minor diameter, when the tool makes a scratch in it, it should fit or almost fit, you may need to do a couple spring passes.
Also the is different classes of fit, 1,2,and 3, the latter being closest tolerance, the nuts from the hardware store may be a 2, while the thread your cutting is a 3 and won't fit based on you threads cut are the size you intended them to be.