Here’s the background story: my Father-in-law had his Nikon D60, with 18-55 VR kit lens attached, on his shoulder when he dropped the lens cap. The cap rolled away and was about to disappear out of reach, so he ran to get it. Unfortunately his Nikon slammed against a metal railing, lens first; the lens came away, would not re-attach and there was no knowing how much damage to lens and camera had been caused.
When it came to me I could see that the whole mount was badly warped and that bits of it had broken off. The electronic connector block was hanging out and the surface which is supposed be flat to mate with the camera throat looked like a tiny roller-coaster track. My F-i-l was going to dump the lens but what he really wanted me to check was the camera, to see if it had been damaged by the impact. My first thought, though, was to save the lens from going to landfill.
It helps that I have taken a few of my own Nikkors apart before, for minor servicing/repair, and so I went straight to remove the whole mount assembly. I found the cause of the severe warp: a tiny lug had broken off inside and was lodged underneath the shims that it had previously been holding in place. I determined that I could get by without this lug, since it was too small for a reliable fix and the shims had one remaining lug to hold them in place before the main mount screws secured them. I re-assembled everything as best I could (the electronic connector block was still a bit loose as one of the screw housings had also broken away) and tested the lens. I had to hold it against the camera body, since two of three mount catches were missing, whilst testing AF, aperture and VR. All seemed to work fine – which was good news because that meant the camera was probably OK too. I feel sure that, had the lens mount been the usual metal instead of plastic, there would have been some significant damage or mis-alignment inside the camera. As it was, the mount absorbed the impact, breaking and warping, thereby saving the camera from any serious damage.
OK, so everything worked, but I wasn’t sure where exactly to get a new mount. I looked for similar lenses on a well-known auction site, being sold for parts, but found none. Thankfully I found a company in the U.S. which sells parts for camera repairs and they had the correct mount for about a tenner. So I ordered it and it arrived a couple of days ago.
The repair itself is quite straightforward. The three main screws are removed, as well as three much smaller screws holding the central sleeve in place. There are two more tiny (but different) screws which hold the electronic connector block in place. There will be a number of shims, which will be specific to each lens and they are to adjust the distance between main mount and optics (i.e., sensor to lens distance). The image below shows the lens barrel, the broken mount to the left, the electronic connector block and, in the background, the inner mount sleeve and shims. Click on any image for a larger version.
Two things need to be done before the main mount can be replaced: the sprung aperture guide is removed to be attached to the new mount as is the small connector with sprung pin, shown near the centre of the image above. Now we’re ready to prepare the new mount.
The aperture guide slots into the underside of the mount and the spring is attached:
The sprung pin is attached:
Then the shims are returned. Notice the guide lug at the top right; there should be another on the bottom left next to a screw hole but it’s missing, so the shims can shift around a bit. This gets fiddly when finally putting it all together as the aperture guide needs to be carefully placed on the correct side of the aperture pin in the lens, otherwise the aperture won’t work at all, but getting the correct positioning can move the shims so that screw holes don’t line up.
With the aperture guide in the correct position and the main screws loosely in place, all that remains is for the inner sleeve to return to its rightful place. Care must be taken with the five tiny screws: two of them have slightly larger heads and a finer thread pitch. It is these two which hold the connector block in place, whereas the other three secure the inner sleeve to the main mount.
After tightening all screws (not too tight – this is a plastic mount, after all), a good clean and mount to camera body, all is well. Focus is accurate and VR works as it should. One more saved Nikon lens to add to my count (OK, that makes two in all – but hey).
One final thought: those shims are thin. Some of them are extremely thin. They are of different thicknesses and will have been put together in that combination for this particular lens and its original mount, so it could be argued that they are no longer an accurate set for this lens. Since all my testing shows focus to be spot-on, though, they appear to be good enough.