The Sta-Tite 97-18 series tuners on the NS instruments are actually pretty good quality. The problem is that they have a nylon (or similar) washer that gets crushed when the tuners are assembled. This washer keeps everything snug, but it adds a lot of friction. Worse, I found that the ones on my Aristocrat tended to stick. By that I mean that when I would try to tune the instrument, a relatively large amount of friction would need to be overcome first, then the normal amount of friction would be present when tuning. That made small adjustments difficult.
The cure for me was to replace the nylon crush washer with a brass shim and a wavy spring washer. The parts are available from
McMaster-Carr. The brass shim is part number 92409A305 and the wavy washer is part number 9714K22.
The guilty washer is under the screw at the end of the worm gear, opposite the key itself. It might be possible to remove it and replace it without removing the tuners from the guitar, but I don't know; I removed the entire set of tuners to do the job. One issue is that they used blue thread-locker on the thread of the screw during assembly. The thread-locker is intended to keep the screw from accidentally coming loose over time, but it makes our job difficult now, especially since the screw head is small and easy to damage. I know from experience that thread-locker will let go if you heat it, so holding a hot soldering iron against it for a few seconds will do the trick. In any case, be sure to use a good screw driver that fits well, not one that's worn or damaged.
Anyway, remove the screw. Remove the nylon washer. Replace the screw with the wavy washer under a shim. No grease or oil is necessary. Now the tuners will turn freely and smoothly.
