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09-22-2014, 01:04 AM   #1
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change a K mount lens into M42?

Yes, the title is correct, I am asking myself and everyone out here:

is it possible to convert a PK lens into a M42 lens? Of course I would restrict it to stop down aperture, no automatic necessary, but I couldn't find anything on the web regarding this. But very much about the opposite, converting M42 into whatever.

The reason is, I have to copies of a very fine Tokina 60-120 in PK, and many M42 cameras, so I am seriously considering this...

Anyone?

Thanks ind advance,

Vranx

09-22-2014, 02:23 AM   #2
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Without having a K lens in front of me, my answer would be "It depends on the lens".

The M42 mount is smaller than the K mount, and usually, the back element sticks out level with or behind the mount area. Whether the lens could be M42 depends, I guess, on if you can get the mount part to fit around whatever sticks out.

I do notice, however, that the 60-120 is available in many mounts, so maybe the back element has a lot of clearance on K and M42.

The actual adaptation sounds pretty hard thogh. Essentially, you take away the K bayonet, replacing it with a custom-manufactured M42 plate, made to spec with regards to the thickness and dimensions of the K plate. These things are made with extreme precision and I wouldn't trust 3D-printed stuff. For the best result, the part should be measured and updated in an iterative process. It might cost quite a bit and I'm not sure who would make/sell it.
09-22-2014, 02:45 AM   #3
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Would it not be easier to get a K-mount camera to go with it? There are plenty out there.
09-22-2014, 04:29 AM   #4
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Yeah, it depends on the back element of the Kmount lens you are looking at. Before you decide to take apart the lens, you should try to track down or make an m42 mount. Mostly you just have to make sure the threads have the right diameter and pitch, and the screw and flange must be of the right thickness. Just look at some m42 lens you have, can you make a clone of that mount? Will the back element of your K-mount fit through the m42 opening?

But yes, like D1N0 said, its probably easier to just buy a K-mount SLR. You would probably benefit a little automation as well, or you can get something relatively cheap and well liked, like the K1000

09-22-2014, 07:28 AM   #5
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The diameter of the K-mount is larger than M42. With the K-bayonet removed the diameter of the rear elements may still be too large to accommodate a screw mount plate. Again this would be have to be checked on an individual lens basis.

You may be able to find a K-mount lens to M42 body adapter or you could have Precise Parts fabricate one for you (if they will ship to you). You would not have infinity focus though.

PreciseParts Build-An-Adapter
09-22-2014, 05:26 PM   #6
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I think the cheapest route is to buy a camera.
09-23-2014, 12:47 AM   #7
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QuoteOriginally posted by dcshooter Quote
I have seen conflicting reports as to whether this lens ever came out in an m42 version. If yes, then do yourself a favor and sell the K and buy the m42. The headaches entailed in switching out a mount will far outstrip any money lost in the transaction. Otherwise, look for another Tokina m42 lens of the same vintage. While it might not be a 1:1 fit, the rear mount may use a similar screw configuration and be easier to shoehorn on. Alternately, buy a T mount to m42 adapter and start working on your lathe and milling machine skills. Also, try to avoid any mods to the lens barrel or original mount, since you will want to be able to reassemble it if you ever want to resell it in original condition.
I have plenty of K-mount bodies and another copy of that lens. It definitely exists in M42 (saw it go in fleabay) but, alas, very rare and extremely expensive.

Comparing it to other M42 Tokinas the screws holding the mount are in the same place and the mount itself seems to occupy a similar amount of length. My idea was to try to get the mount from an otherwise defective Tokina M42 lens and try to fit it. If it doesn't fit, the K mount can easily be put back. But I was hoping someone out there would have tried this already...

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