Several of the cheaper "kit" lenses offered by Nikon have plastic mounts. While these lenses have great optical quality, a number of us have managed to break of one of more of the platic mounting tabs. I recently replaced the mount after I managed to break off one of these tabs (I was clumsy and dropped my D40x about 6 inches, onto a carpeted surface). The cost of replacement part was around 17 dollars, including shipping. A new lens would have been over 100 dollars. The actual lens that was repaired is the 18-55mm G series zoom. I also have a 55-200mm zoom, and it has the same plastic mount.
Step 1: Order/obtain Replacement Lens Mount
I got mine from Nikon usa for about 17 dollars including shipping. Please take note of the screw, brass plate and chrome mounting post in the left side of the first photo. These are included with the replacement part. I removed these and used the existing ones instead.
Step 2: Prepare Tools and Workspace
The only tool needed is a small philips screwdriver. I placed everything on a large sheet of white graph paper to be able to see the screws more easily. A cup or saucer to hold these screws is a very good idea. Pictured is the lens, screwdiver set and the replacement lens mount.
Step 3: Remove 8 Screws Holding Lens Mount in Place
There are 8 screws to remove. 3 larger screws can be seen in the first photo. There are 5 smaller screws that face into the axis of the lens, remove all 8, keeping track of where they came from.
Remove the inner piece as shown, setting it aside. Keep track of your screws.
Step 5: Rotate CPU Contact Plate In, and Pull Mount Out
Gently rotate the CPU contact plate in as shown (it is attached with with a ribbon cable). pull the lens mount out carefully, and let is flop as shown. It is still attached with the white wire.
Step 6: Unscrew Bad Mount From White Wire
Unscrew the bad mount from the white wire and mounting bracket as shown. Remove and set aside the bad mount.
On the replacement part, unscrew the same mounting bracket. you only need one, so use the one that is still attached to the lens. Screw the bracket to the replacment mount. Verify that the new part is attached to the lens and the old part is not. You'd hate to have to do this all over again.
Step 7: Re-assemble
1. insert new replacement mount
2. rotate CPU contact plate back to its proper position
3. insert inner part removed earlier
4. tighten screws (do not over-tighten)
5. test lens
6. have a cold one (Important)