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It should fit tight. It is very tight on the D4. I've had it fall off the D3 because I put it on with the lens hood reversed. This made me tighten it with my hand partially on the focus ring. I thought it was attached, but it did not lock on.
There is another problem with the lens and it caused my lens to fall apart. The screws that hold the lens flange to the lens worked loose. I had my lens on a D3s and in my bag. I opened the trunk, took the camera (lens attached) from the bag and the lens fell off. A bunch of shims, washers, and other things went everywhere. I looked at my camera and only the lens connecting plate and a thin, black piece of metal stuck out. The lens was a mess. Nikon fixed the lens without cost to me. So, check those screws periodically.