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02-05-2014, 08:04 PM   #1
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Problem/question about m39 -> m42 adapter

Hi, so I have a quick question about my m39 - m42 adapter.

I just received a 50mm/3.5 industar lens and was all excited to use it. But when I screwed the adapter ring into the pentax k mount to screwmount adapter, it would only go in about half way. (see pictures). The screwmount adapter I have is an original one, from pentax, but the other adapter ring was just on I bought on amazon. When I screw everything together, there is a fairly large gap between the lens and the screwmount adapter. It will only screw in more if I really force it, and even when I do I can only get it in slightly more. Check the pictures to see what Im talking about.

Whats going wrong here, is it supposed to be like this? was the m39-42 adapter manufactured incorrectly? and what can I do to fix this problem?


Thanks for your help

This is the adapter I got

Amazon.com: Fotodiox 07LAm39m42 Lens Mount Adapter, M39 to M42 (39MM - 42MM Thread) Adapter for Leica, Canon, Nikon, Carl Zeiss, Pentax, Leica: Camera & Photo

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02-05-2014, 08:10 PM   #2
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I believe there were more than one M-39 specifications. It may be that the thread pitch on your adapter does not match the thread pitch on the lens.
02-05-2014, 08:13 PM   #3
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I would first off check the threads.

It looks like the issue is the M42-M39 part correct? (ie: the K mount bit fits the camera fine, and the M39 bit fits the lens fine, but the 42 to 39 part won't screw on)

Have a look at the threads, check for dirt, metal flecks (perhaps it wasn't cleaned up too well after machining) and also check for damaged threads. Perhaps it has been dropped/knocked and a thread broke.

Other than that, all I can think of is a machining issue (perhaps they put thr wrong pitch thread on there? M42 should be 42mm with a 1mm pitch if I recall.
02-05-2014, 08:15 PM   #4
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Also be aware that the Russian made stuff sometimes had some "interesting" tolerances....

And 50 years doesn't improve them.....



I'm in the process of Restoring a 1959 Zorki 5 (with the same lens as you) and while the machining inside looks pretty good, the fitment is a bit agricultural.

02-05-2014, 08:20 PM   #5
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thanks for all the advice, ill definitely take a closer look. If everything goes bad, and its machined incorrectly, do any of you know of a reliable, well rated, m39-m42 adapter?

and yes, to answer one of you, I think the problem is definitely with the m39/42 adapter because the other is genuine pentax from B&H

thanks for the help!
02-06-2014, 09:06 AM - 1 Like   #6
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I believe there are two very similar 39mm threaded mounts used by different makes of Leica clones: M39 and E39. The M39 has 1mm thread spacing, while I believe the E39 uses "inch" thread spacing - probably 25 tpi. With a bit of play in the threads either will fit the other, but when tolerances are tight you get results like you show.
02-06-2014, 09:40 AM   #7
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A slightly mismatched thread pitch (e.g. 1mm vs 24 or 26 tpi), even if everything is with standard tolerances, would most certainly explain why it will screw in part way but not completely.
02-06-2014, 09:56 AM   #8
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so do you think its worth trying another 6 dollar adapter ring?

02-06-2014, 10:02 AM   #9
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Based on what TomB posted, I would want to identify the thread pitch of the one I had and make sure the new one was not the same.
02-06-2014, 10:18 AM   #10
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QuoteOriginally posted by TomB_tx Quote
I believe there are two very similar 39mm threaded mounts used by different makes of Leica clones: M39 and E39.
I may be misinterpreting the photos, but it appears that the M39 thread of the M42/M39 adapter fits the lens perfectly, but the M42 thread is wrong and is different than that of the K-mount/M42 adapter.

Fotodiox is an established brand. I would be more suspicious of your "Made in Philippines" K-mount adapter. Does it fit other M42 lenses?


Steve

Last edited by stevebrot; 02-06-2014 at 10:28 AM.
02-06-2014, 10:23 AM   #11
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QuoteOriginally posted by hks_kansei Quote
I'm in the process of Restoring a 1959 Zorki 5 (with the same lens as you) and while the machining inside looks pretty good, the fitment is a bit agricultural.
I just noticed that the lens does indeed appear to be the LTM version of the Industar-50*. As such it will not work on a SLR except for close focus due to its being designed for use on a rangefinder camera such as the Zorki-5.
Edit: Appearances are deceiving. Although the rear of the lens looks to have the rangefinder coupling collar, the physical size is much smaller than the I-50 intended for rangefinder use. It is definitely the Zenit SLR version.


Steve

* The SLR versions of the I-50 was only made in M42 mount
Edit: I was mistaken (brain fart), the original lens for the Zenit-S was indeed the I-50 in M39 (Zenit) mount.

Soviet and Russian Cameras - Zenit-C

Last edited by stevebrot; 02-06-2014 at 01:51 PM.
02-06-2014, 12:26 PM   #12
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QuoteOriginally posted by stevebrot Quote
Fotodiox is an established brand. I would be more suspicious of your "Made in Philippines" K-mount adapter. Does it fit other M42 lenses?
Umm, it's the Genuine Pentax Adapter K...
02-06-2014, 12:30 PM   #13
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QuoteOriginally posted by stevebrot Quote
* The SLR versions of the I-50 was only made in M42 mount
There were Industar 50s made for M39 Zenit SLRs.

Zenit 3M

Last edited by boriscleto; 02-06-2014 at 12:35 PM.
02-06-2014, 12:36 PM   #14
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QuoteOriginally posted by boriscleto Quote
There were Industar 50s made for M39 Zenit SLRs.
You are correct, the original normal lens for the Zenit-S was the I-50 in M-39 (Zenit). Either way, the pictured lens looks to be LTM. You can tell by the extension on the rear to engage the rangefinder coupling. Edit: Apparently not the case. The LTM version can be told by the difference in physical size. The Zenit lens is essentially a pancake.


Steve

Last edited by stevebrot; 02-06-2014 at 01:48 PM.
02-06-2014, 12:44 PM   #15
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QuoteOriginally posted by stevebrot Quote
The references I am aware of show M42 only for Zenit SLR. Either way, the pictured lens is LTM. You can tell by the extension on the rear to engage the rangefinder coupling.


Steve
See the link in my edited post. The Industar 50 was the kit lens for the Zenit3 SLR in ZM39.
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