A spanner key can be purchased from aftermarket suppliers, like Peter Atwood, who is immensely popular for his keychain tools - and therefore hard to get.
The SnG uses Loctite on the threads, I understand soaking in hot water is necessary to loosen the bond. Once free, the pivot can be adjusted to the user's taste. My SnG has been going hard for aobut two years now, and I haven't needed to mess with it. Most knives don't get out of adjustment when used responsibly. At least the screw pivot allows adjustment every few years or so.