[bambill]

Actually I would suggest that most failures occur because people do use a torque spec.
Seen it all to often, the tapper lock binds, you hit your torque spec, next thing you know it is loose again.
Never fit new tapper lock dry. Use plenty on anti-seize on the inner and outer of the tapper lock, also on crank thread, and also the back of the nut, nothing can then bind up.
Get it as tight as you can, then get a hammer and smack it around the outer edge of the nut and then tighten again.
Do that 3-4 times, you will be amazed how much further you can do the nut up when doing this.

 

[bambill]

Nah, never had to use locktite.
Done heaps as I have described above with no issue.