Nikon bayonet mount and lens screws

[Sierra Club]

I have tried searching the forums but it seems it's either me failing at keyword searching or this (quite interesting) subject was not discussed in detail yet.

As in the title – I’d be interested to hear whether anyone here has managed to find a good modern replacement for Nikon's OEM bayonet mount screws? I have re-lubed and cleaned a couple of Nikkors (including 50 f/2.8 AI-S and 28 f/2 AI-S) and all I can say is that by pure luck only have I managed to keep the screw heads undamaged. To me, disassembling and cleaning CRC optics isn’t as nerve racking as unscrewing the bayonet mounts on some of the never serviced Nikkors. Even treating them with isopropyl alcohol to dissolve factory used thread locker and using JIS-type screwdriver isn’t a guarantee of success.

Having another used AI-S lens waiting in line for cleaning, this time with already damaged screws, I have decided to look for replacements so maybe I can return it to somewhat better condition. I have looked on the Internet and it seems I’d have to order by ton from either China or Japan and also guess some of the key dimensions like thread pitch (it seems new AF-D and AF-S lenses have different thread pitch and length than old AI and AI-S Nikkors).

I’d greatly appreciate if you could share your experience and advice especially if you’ve already repaired and successfully replaced screws in your lenses 🙂

 

[dourbalistar]

Sierra Club, have you seen Richard Haw's wonderful Classic Nikon Maintenance Site? He has an article about screws and drivers that might be helpful:
https://richardhaw.com/2015/12/29/best-practices-part-1/

He also has a post about Nikon bayonet screws, but not sure if he mentions where to source replacement screws:
https://richardhaw.com/2017/03/26/repair-nikon-bayonet-screws-video/

 

[Sierra Club]

Thanks Dourbalistar,

I've sure checked out almost all of Richard Haw's tutorials and repair articles. I have to admit there's a wealth of really useful details there and it's awesome that he shares his expertise in this way (motivated me to relube an old Micro Nikkor which now works perfectly).

I did see that article on replacement screws as well - this was my starting point and I have ordered samples from many different online hardware/hobby shops only to find out that either the screw heads were of incorrect shape and rised above the surface of the lens mount ring or that they were of incorrect diameter (although the dimensions of the thread were perfect) and they didn't sink/fit properly in the machined holes. I did find one version which fits nicely but it's slot headed and makes AI-S lenses look like pre-AI and the seller has ran out of them after I bought just 5 for testing 😀

I was hoping that maybe someone knows a good place where I can buy correct replacements without worrying if they will fit. I guess I have to do more research or buy a lathe hahah.

Thanks again though!

 

[Ronald M]

Thanks Dourbalistar,

I've sure checked out almost all of Richard Haw's tutorials and repair articles. I have to admit there's a wealth of really useful details there and it's awesome that he shares his expertise in this way (motivated me to relube an old Micro Nikkor which now works perfectly).

I did see that article on replacement screws as well - this was my starting point and I have ordered samples from many different online hardware/hobby shops only to find out that either the screw heads were of incorrect shape and rised above the surface of the lens mount ring or that they were of incorrect diameter (although the dimensions of the thread were perfect) and they didn't sink/fit properly in the machined holes. I did find one version which fits nicely but it's slot headed and makes AI-S lenses look like pre-AI and the seller has ran out of them after I bought just 5 for testing 😀

I was hoping that maybe someone knows a good place where I can buy correct replacements without worrying if they will fit. I guess I have to do more research or buy a lathe hahah.

Thanks again though!

I think you need to heat the screw to soften the thread locker.

Another source is bargain grade lenses from KEH or
USED PHOTO PRO. UPP sells good condition lenses
pretty cheaply.

 

[dourbalistar]

I think you need to heat the screw to soften the thread locker.

Another source is bargain grade lenses from KEH or
USED PHOTO PRO. UPP sells good condition lenses
pretty cheaply.

Bargain grade lenses are actually pretty nice from KEH or UPP, but I guess harvesting the correct screws from an UGLY or AS-IS grade lens could be one way to do it.

 

[Sierra Club]

I think you need to heat the screw to soften the thread locker.

Yeah, that's one way to do it but it has two downsides to it. One is that I don't really feel comfortable with hot soldering iron in the proximity of the, rather rare, lenses (not to mention that unevenly applied heat may warp the bayonet ring which, i think, is machined to high precision). Second - there was also mention of putting entire lens in the oven to heat the screws and break thread locker - this just sounds like asking for trouble with lubricant leakage and balsam separation.

I did give this some thought and still think that it would be ideal and safer to find correct screws as they must be hiding somewhere out there 😀

Bargain grade lenses are actually pretty nice from KEH or UPP, but I guess harvesting the correct screws from an UGLY or AS-IS grade lens could be one way to do it.

Fully agreed on the good condition of the KEH lenses, I'd rather clean them and use them than treat them as donors. Granted - there are other sources where lenses damaged beyond recognition may be obtained - but still, it's quite often that first thing these lenses have damaged are lens mount screws.

This, however, may be a good way to harvest some "bunny ears" screws as well as the very small (anodized or painted black) aperture ring screws.

It's weird how large number of old Nikkors have these screws damaged and how a wide variety of screws can be bought everywhere yet it's so hard to come by a proper replacement. I'll find them sooner or later though!

 

[View Range]

I have taken the bayonet mounts off of about 36 lenses to cut the rear ring for AI. The trick always for me has been to generate enough torque on the screw driver while applying enough force to keep the tip in the slot. The solution I use is to grind/file normal hex shank driver tips that are used with common electric drills to give precise fit in the Nikon screw heads. A lot of grinding/filing is required because of the mismatch in the initial sizes. I do this for both straight slotted and Phillips head tips, and several slightly different tips are needed. I then mount the hex shank tip in a high quality tap handle. I use a Craftsman ratcheting tap handle. This allows adequate/controlled torque to be applied. With this arrangement the screws come out easily. I have never had to heat any screw.

 

[Dwig]

... Even treating them with isopropyl alcohol to dissolve factory used thread locker ...

Use acetone, not isopropyl alcohol.

 

[Sierra Club]

I have taken the bayonet mounts off of about 36 lenses to cut the rear ring for AI. The trick always for me has been to generate enough torque on the screw driver while applying enough force to keep the tip in the slot. The solution I use is to grind/file normal hex shank driver tips that are used with common electric drills to give precise fit in the Nikon screw heads. A lot of grinding/filing is required because of the mismatch in the initial sizes. I do this for both straight slotted and Phillips head tips, and several slightly different tips are needed. I then mount the hex shank tip in a high quality tap handle. I use a Craftsman ratcheting tap handle. This allows adequate/controlled torque to be applied. With this arrangement the screws come out easily. I have never had to heat any screw.

That's valuable advice! Thank you View Range. I do have a couple of Wera JIS screwdrivers but I have also noticed that even those need to be filed a bit to ensure better fit with Nikon screws (these must be really odd screws). These small screwdrivers are rather hard to control. And yes, proper amount of downward force seems to be essential as the cross notches in those screws are rather shallow and the material in general seems rather soft, it deforms very easily. I'll look around for some tap handles and see if i can replicate your solution - sounds promising. Thanks again for sharing your insight.

Use acetone, not isopropyl alcohol.

Is there any proof that acetone works better than IPA for softening/dissolving solidified threadlocking compounds?

I know for sure that IPA is definitely less agressive, especially when it comes to rubber and plastics and I have used mainly out of caution to avoid damaging any such parts. Of course I apply such solvents rather sparingly so there should be no significant risk even with acetone. I think I'll try both acetone and IPA on a drop of solidified Loctite to see which one does the job better. Thanks.

 

[Sierra Club]

So I went and ordered some more variants of M2 phillips screws (the ones at the top are M1.4)...

... none of them fit either bayonet mount holes (M2) or bunny-ears coupling prong holes :bang:

Of course none of them look like the drawings on the spec sheet.
They were supposed to have very flat heads so they would sit flush with the bayonet ring surface.

I'm really tempted to custom order the properly machined ones and be done with it, but the MOQ is 200,000 haha.