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10-24-2012, 09:18 PM   #1
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How I convert M42 for use on Pentax K

I really hate the M42 Pentax adapter that required me to stick my fat finger in the front of the camera to unlock the adapter.

Others have shown how the spring can be taken off the adapter and the adapter screwed firmly (permanently) onto the M42 lens which allows the lens to be used more or less like a standard K mount. There is the issue though that the lens is not really locked to the camera and they can come adrift in a heart stopping event. One solution is to drill or cut a notch in the rear of the lens so that the camera pin locks securely, this works provided the lens body has enough diameter at that point (about 50% seem to not). It is really hard to drill a neat notch in exactly the right place!

I have a Zenit Fotosnaiper with the Tair 300mm lens. It has an M42 mount which does not have enough diameter to drill for the locking pin and neither does the lens body contact the camera's electrical contacts ('though I am not sure exactly how significant this might be?).

This is how I did it for the Fotosnaiper lens;

This is the back of the lens with the M42 mount removed...



I have cut an aluminium ring to fit over the part of the mount that is too small diameter to be drilled for the lock pin. It is much easier to file a notch in the ring than it would be to drill the back of a lens...



This is the ring having a trial fit over the mount and an extension tube being used to simulate the camera mount.



The ring is a loose fit on the mount so once everything had been tested for fit I put a dab of epoxy between the ring and the mount then used the extension tube to hold everything in place and to ensure the locking pin slot was in the required position.


John

10-24-2012, 09:56 PM   #2
hcc
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Good on you. Thank you for sharing.

By the way, please check your PF personal details. I did not know that Christchurch was spelled like that:
"Location: Near Christchruch New Zealand"
10-24-2012, 10:24 PM   #3
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Now for your next challenge, I propose you invent a way to weather seal the lenses modified this way!
10-24-2012, 10:31 PM   #4
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QuoteOriginally posted by hcc Quote
Good on you. Thank you for sharing.

By the way, please check your PF personal details. I did not know that Christchurch was spelled like that:
"Location: Near Christchruch New Zealand"
He he, things are still a little shook up around there..

10-24-2012, 10:34 PM   #5
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QuoteOriginally posted by Eulogy Quote
Now for your next challenge, I propose you invent a way to weather seal the lenses modified this way!
I suggest what we used to do with moto cross cycle magnetos and cover the entire ensemble with Plasticine.
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