[TowerTalk] Noob question re: Thrust Bearings

[scott at nx7u.net]

I've never found any clear explanation of how thrust bearings are 
practically implemented.
If the bearing is to "hold up" the antenna (so that the rotator doesn't 
have to), I assume that it's the force from the four radially-oriented 
bolts that do so?  It seems to me that over time the mast would slip.  
Is that really not an issue with sufficient bolt torque?
It seems to me that the mast should be pinned through the bearing 
instead--that is, a through-bolt that goes through holes drilled in the 
mast.
What obvious (but not to me) thing am I missing?
Thanks,
NX7U
45 years active & never had a rotator bigger than Radio Shack :-)