"Name Brand" M26 Adapters & Tolerancing

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J_Rogers
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Joined: Mon Aug 09, 2021 2:29 pm
Location: North Carolina, USA

"Name Brand" M26 Adapters & Tolerancing

Post by J_Rogers »

I hope this is the correct location for this post, as this is more of an open ended question seeking discussion.

What is the general consensus on using M26 (m26x36tpi & m26x0.706) adapters from companies such as Edmund Optics / Thorlabs on Nikon's M26x0.75 threads? I have searched almost endlessly for a specific mention of either of these in use and have come up short. Most posts mention the source as either eBay or RAF. I know that they are two completley different threads but I find myself needing a good-enough for the time being solution until the holiday shipping commotion settles.

Here is the post comparing the three different threads with another post showing Mitutoyo tolerances: Nikon and Mitutoyo objectives have different M26 threads. And here is tolerancing data found on Thorlabs site (This was a pop-up on a specific adapter w/ no way to hyperlink to the page)
thorlabs thread tolerance.png


So, does anyone have any experience using EO/Thorlabs adapters for Nikon M26 threads? Am I missing a major US distributor for optical components that may have said adapter?

Scarodactyl
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Joined: Sat Apr 14, 2018 10:26 am

Re: "Name Brand" M26 Adapters & Tolerancing

Post by Scarodactyl »

Just checked, my Thorlabs 32mm to 26x0.71 mm adapter does bind up with a Nikon 26mm, at least the one bd plan 40x bound in the one adapter I tried--two turns and then it's stuck. It'd be functional I guess but it's hard to remove the nikon objective. Most Nikon nosepieces seem to accept either m26 without issue, but one exception I had was an epi DIC nosepiece where some Mitutoyos would thread in fine and others wouldn't(??). I had that nosepiece serviced by ny local microscope guy who speculated it was not entirely made by Nikon given some odd features (different bolts among other things) so maybe that's involved.
Last edited by Scarodactyl on Sun Dec 12, 2021 6:02 am, edited 1 time in total.

Chris S.
Site Admin
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Re: "Name Brand" M26 Adapters & Tolerancing

Post by Chris S. »

J_Rogers,

I use an Edmund Optics M26 ("Mitutoyo") adapter to mount Mitutoyo objectives in my infinite rig; in this use, the full suite of Mitutoyo M26 objectives unsurprisingly fit perfectly in this adapter. I do have one Nikon M26 finite objective, but for obvious reasons, I've never mounted it on the infinite rig (when I use this objective, it's on a bellows with other mounting bits). But I can certainly test this Nikon objective's fit for you on the EO adapter. Unfortunately, I won't be home, where my rig is, for 7-10 days, so can not test immediately. From your post, it seems this amount of delay may not work for you?

If you can afford to wait this long, please let me know.

(My gut feel--nothing more--is that most M26 mounts should work decently for both Nikon M26 and Mitutoyo M26 threads, different though they are.) As you'll note from the test images you linked to (which I know well) only about two threads out of the objectives/adapters' four or fewer threads seem to actively engage. This limited engagement seems likely to permit significant tolerance--likely plenty to accommodate a 54/1000mm difference between the two main threads. Any adapter that lacks 54 microns forgiveness is tightly controlled indeed--likely controlled beyond useful benefit.

Sorry I can't provide empirical data just now! :D Again, please let me know if a test in about 10 days or so has use to you.

[As for post location, I think that either the "Techniques" or "Equipment" sections of the forum may better fit this subject. Admin can move this thread once everyone has seen this notice.]

Best,

--Chris S.

J_Rogers
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Location: North Carolina, USA

Re: "Name Brand" M26 Adapters & Tolerancing

Post by J_Rogers »

Chris S, no worries if you are unable test it within the next week or so. Keep us posted with the results, since the EO adapters are nearly triple the price of the equivalent Thorlabs mounts. For the time being I think a variable size lens mount could be the most practical solution for my time crunch. I have a number of Nikon MM objectives on their way and quickly need to test image quality before flying out to see family for Christmas (the bad ones are going to be a gift.) To my surprise there is not a single seller, company, or distributor in the US currently selling an adapter with m26x.75 threads.

Scarodactyl, thanks for that info. I speculated that neither of the two would thread fully since both companies actually have a set of defined manufacturing procedures geared more towards the precision optics side of things. But don't Nikon DIC objectives use m25x.75 and not m26? If so it really starts to bring the question just how tight of tolerances does Nikon have. For instance I have 3 manual focus Nikkor's that will thread directly onto an SM2 lens tube no problem, yet a newer autofocus will not seat (all 52mm.) Whereas that El-Zoom Nikkor has some insanely tight threads; I took the massive main flange off the back and couldn't get it back on. Spent 30min under a microscope trying to find what was causing it. Turned out to be a piece of lint from the microfiber I used to wipe it down.

Scarodactyl
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Joined: Sat Apr 14, 2018 10:26 am

Re: "Name Brand" M26 Adapters & Tolerancing

Post by Scarodactyl »

It was an epi DIC nosepiece for bd plans (m26x0.75)--I actually have another one coming in soon. I don't think Nikon has used that thread again since the finite era.
If you need them quick see if you have a friend with a 3d printer (fdm). Thread adapters are pretty easy and usually only take a couple iterations. Heck, I could probably make one up for you if you need it that quick.

I could probably 3d print an adapter for you, depending on what you need the other thread to be. I use them myself and havem't had issues but of course it would come with no guarantees of not dropping your lenses or setting them on fire or whatever.

patta
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Re: "Name Brand" M26 Adapters & Tolerancing

Post by patta »

26mm with 36 TPI, sounds like an obscene hybrid, who invented it?
It is like to say that I'm one meter and three foots tall!

Scarodactyl
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Joined: Sat Apr 14, 2018 10:26 am

Re: "Name Brand" M26 Adapters & Tolerancing

Post by Scarodactyl »

patta wrote:
Wed Dec 15, 2021 5:26 pm
26mm with 36 TPI, sounds like an obscene hybrid, who invented it?
It is like to say that I'm one meter and three foots tall!
Standard RMS pitch with a different diameter. Olympus's neo splans probably came a bit earlier than mitutoyo's objectives, but I don't know the exact chronology or if there was an earlier predecessor.

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