they get installed with Loctite
As a millwright at a seminar from Loctite, we learned that Loctite 242 increases break free torque by 5 foot pounds, which is not very much.
Just though you might find that interesting, however...
If very fine threaded aluminium threads, such as those on a Triumph Bonneville timing case, the 242 will actually rip the threads out, believe it or not.