The supposedly universal M42

[Nesster]

In my bottom feeds, I've accumulated a few M42 mount lenses. Most of them are fully interchangeable, compatible with my Spotmatic SP1000, Fuji ST605, both Pentax and Bower M42->K adaptors, the Vivitar extension tubes, and the Pentax bellows.

But there are exceptions:
The Fuji 55/2 that came with the ST605 isn't happy with the Spottie or the adaptors, there are bits sticking out the back.
The S-M-C Tak 28/3.5 will NOT mount on the Spottie, and the Pentax adaptor. It mounts in the Bower and the tubes and bellows however. I think there's a thread out of whack on it.
The Auto Rikenon 28/2.8 that just arrived came with a thin plastic shim on the mount. I wondered about that. Without it, on the Spottie, it screws PAST 12 noon and settles 45 degrees beyond. With it, it stops at 12 noon, but will NOT get infinity. Haven't tried this with the ST605 as yet.

It's funny but it may turn out that the Fuji is the most compatible of my cameras.

[luisalegria]

There are other cases -

Mamiya SX lenses (also resold under other brands) won't go on several M42 cameras and pretty much any adaptors, as they have another pin sticking out. This clears the mount on Pentax Spotmatics and some others with protruding mounts, but unless the pin is removed they won't go on others, if the mount protrusion is too small or too wide, or flush, like M42 adapters.

My S-M-C 28/3.5 does go on my Spotmatics though. Odd that you had that problem.

[Nesster]

It is very odd, I think one of the threads near the lens body has been pulled out of true. My Super 28 works fine, as do all my other S-M-Cs, so it's really this one sample.

I'm still scratching my head about the Rikenon, maybe someone put the bottom on the wrong way.

[orly_andico]

I have a Fuji 55/2.2 which came with an ST605N. I don't have a Spottie but it works fine on an M42-K converter on my K10D. Of course the K10D has a much smaller mirror than a Spottie...

[LucisPictor]

That's werid. All the M42 lens I have tried, fit on each M42 cam (Spotty, Spotty II, Zenit EM, some Prakticas) or adapter I have.

[peterqd]

[Nesster]

The case of the Rikenon rings a bell quietly, far off... I almost remember this from somewhere.

I looked at the lens some more, and it's the damnest thing. I wonder if there was a version of the Ricoh where the registration was a bit different, or the mount, or something.

The mount looks to be fixed via three screws, but it screws 45 rather than 66 degrees past 12. At any rate, the aperture pin is correctly aligned with the A/M and focus points, and the infinity stop lines up with everything. It does seem like the whole lens is internally consistent.

If I rotate the mount by 1/3 I'd have to equivalently rotate the other barrel elements... my mind boggles. I'll probably leave it alone, do a resolution/image comparison, and only consider fixes if the lens turns out superior to all my other 28s.