Replacing lens mount on 300/2.8 AIS

<p>I have an old 300/2.8 AIS manual focus lens with a badly worn mount. It's down to the brass in many places and the lens therefore doesn't fit all that tight onto a body.<br>

I took it to a local repair place and they said they couldn't get the part to fix it. Are all nikon lensmounts different, or could I replace the mount with one from a different lens?<br>

Aside from that, does anyone know if Nikon still makes parts for these older lenses? The lens I have is the last manual focus version.</p>

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<p>Are all nikon lensmounts different ...</p>

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<p>In a word, yes. Specifically the aperture stopdown lever (which is an integral part of the mount) is different for each lens. This mechanism is also secured to the mount in several different ways. One might be able to modify a mount from another lens to fit the 300/2.8 by swapping stopdown lever parts, but the question is ... which mount?</p>

<p>As an example, the mounts for the AI 50/1.8, AIS 50/1.8 ("long nose"), AIS 50/1.8s (sold only in Japan) and AIS 50/1.8 "pancake" are all different, even though they are nearly identical optically.</p>

<p>best is to grab the same lens on ebay that is being sold for parts and replace the mount.</p>

<p>I purchased a mount for my 300 2.8 AIS direct from Nikon about three years ago. Just call Nikon parts in El Segundo and order one. I think it was about seven bucks. They had hundreds in stock then, and I'd be surprised if they were sold out now.</p>

<p>Have you contacted Nikon parts to see if they have the mount yet? I got a new mount for my 400mm f3.5 about a year ago from Nikon. In my case I had to also buy the light baffle that attaches to the mount. The reason was that my lens, which I purchased used had an AI mount on it when I bought it, even though according to the serial number and the orange minimum aperture and ADR numbers my lens is AIS. Apparently the baffle design was changed between the AI and AIS versions of the 400 f3.5, or perhaps the previous owner put a mount and baffle from another lens, (like the 300 f2.8), on my lens. As I recall the mount and the baffle were each about $40, which didn't seem unreasonable to me.</p>

<p>Michael, your right that they are different (especially for those 50mm) but for the EDIF lenses the differences are small to inconsequential. The stop down lever mechanism is based more in the body of the lens and the mount is just a mount, rather than a more complicated intergrated mount.<br>

I'd try the Nikon part angle first, Nikon made a fair bit of spares for those long pro lenses. I think they expected a lot more either repairs or wear and I think most shooters took a bit more care. That said I had a 300/2.8 that I was the 4th or 5th pro owner, and it was pretty beat when I got it and beat on it some more, and I got a replacement mount and apeture blade/plate for it as well. It was a 1st series AiS, probably 8-10 years older than the OP lens, and even though it was a few years back Nikon had the parts, no problem. I'd change those mount screws as well, they are extra long for the ED-IF lenses and cheap insurance.</p>

<p>Thanks for all the advice. The local place I took it for repair didn't seem so knowledgeable. I'll check with Nikon parts.</p>

<p>Hi, try to take the lens mount measure the thickness with micrometer and look for an old cheap lens.Their bolt pattern are the same . Make sure the thickness use shim or machine if you can't find the same thickness. I did it with my 600mm f4 ais I replaced it from my 135mm 2.8 series E non ai and it works. </p>