Paul, only collet chucks that are precision engineered have this two "locking" points. It is due to the perfect fit of the tapers, they lock together like Morse tapers do in a drill press/lathe etc. Loosening the nut the first time still leaves the tapers stuck together and it's only when the "free" thread use used up the the next turn with the spanner breaks the seal. In spite of the original chuck being as good as they get in mass produced routers, 99% of woodworkers who use a MUSCLECHUCK are like me and wouldn't ever go back to a conventional chuck.
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