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Author Message   Nickon51 Tinkerer Username: Nickon51 Post Number: 144 Registered: 05-2008 Rating: N/A Votes: 0 Posted on Sunday, July 17, 2011 - 11:43 pm:    Well the bad news is I don't own one of these lenses so can't specifically help. In general terms, screw the ring back in and check for damaged threads where it has to screw past. Also check that there are no locating pins protruding from the slots in the diaphram housing. As you unscrew that ring, examine carefully that it is the only thing that is turning, that there is no other component inside or underneath that is moving as well. For lens spanners, I use a piece of industrial hacksaw blade ground to the right length and thinned to fit the slots. You can get some torque good torque if you really need to. Best of luck Greg