Industar-50 (1964) thread pitch question

B

brankop

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Hello all,

I have two lenses Industar-50 3.5/50 from 1964. What is the thread pitch on them: 1 mm or 1/26 inch?

Thanks

B.
 
Only the pre-war FED lenses were a non-Leica-standard thread. All the Industar 50s would be the standard thread (I think that's the 26tpi). They should mount ok on any Leica, Zorki etc but may not be compatible with pre-war FED bodies.
 
If something appears to be wrong, it probably will not merely be the thread pitch (which ought to be LTM, i.e. M39x1/26", on all their post war rangefinder lenses), but the register depth as well - the Industar 50 was the standard lens on the early Zenit SLRs, whose first mount was LTM in width, but 1mm pitch and with a long (45mm) register distance to make up for the mirror box.

And be aware that the quality control in the USSR was driven by the government requirement to churn out large numbers of a product - when behind, they packed and shipped even broken or incomplete lenses. I've seen some lenses with mis-cut or even entirely missing threads.
 
Industar 50 (chrome collapsible or rigid) is ZM39x1 (early Zenit SLR fit) and rarely, m42 screw

The LTM version is exactly the same lens, it has a spacer attached tae achieve infinity on rangefinders. Ye simply unscrew the spacer tae reveal an identical lens tae the SLR version.

Industar 50-2 (black pancake) is M42 screw.:cool:
 
Thanks all,

I attempted to measure the thread pitch by using 100x microscope and an manual microstage. The best that I could do is to measure a distance between three treads and then divide result by 2. Where is exactly the center of a thread is a bit hard to determine due to wear of the thread. Here are the results:

Lens 1: average thread pitch: 0.934 mm

Lens 2: average thread pitch: 0.895 mm

Both lenses are from 1964.

I would not consider this an issue, but I am making an adapter for the lens so I can do proper measurement on the optical bench.

Best,

B.
 
Just a question,

Just a question,

Hi,

No one ever mentions screw gauges in replying to threads like this and I've not seen them for sale for years; well, since we were burgled.

Any thoughts out there?

Regards, David
 
I'm 99.9% sure all the USSR 39mm lenses are 1mm pitch, not LTM 26tpi. Certainly the Zorki-4k manual gives the thread as being 39 x 1mm.

I've attempted to confirm with thread gauges, but there are not really enough threads to do it (and the aforementioned poor quality control does not help!) brankop's method could work better, but his figures actually give more than 26tpi - a combination of wear and poor QC?
 
The plot thickens

The plot thickens

Hello all,

I decided to approach the lens thread conundrum from the camera side: I measured pitch of the Zorki-6 mount by using 100x microscope and manual microstage with 5um resolution. I was able to focus onto 4 threads and measured distance is 1.02mm per thread.

In order to check my microstage, I measured thread pitch of a known screw and got the second decimal right (1/100 of mm).

The camera is also from 1964.

Please advise,

B.
 
brankop said:
Hello all,

I decided to approach the lens thread conundrum from the camera side: I measured pitch of the Zorki-6 mount by using 100x microscope and manual microstage with 5um resolution. I was able to focus onto 4 threads and measured distance is 1.02mm per thread.
Click to expand...

That looks as if it were 1mm - still, all post-war FSU lenses I have or had did fit my Leicas and LTM adapters (while owners of pre war lenses and cameras have often reported their incompatibility). But at usually only four to six threads on the mount, the end-to-end difference between imperial and metric is a mere 10-15%. The pre war incompatibility and later compatibility with LTM might also be explainable if they went over from tight to loose fit at that threshold.
 
Do the lenses screw into the Zorki 6 mount okay? If so, then duplicate the thread form in the mount. The threads are only really there to stop the lens falling off the camera - they have no bearing on optical alignment provided they allow the rear of lens to mate properly with the mount.
 
FYI, a mechanical engineering technician with a right tool measured the thread pitch from Zorki 6 mount and determined M39 x 1 mm pitch. The optical bench mount will be based on this dimensions.
 
39x1. David, really, you had a thread gauge? I used to have one too, but mine is lost to misplacement, not the violation of criminals (sent to untimely deaths if I had my way, best I don't have my way?).
 
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