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12-29-2015, 09:48 AM   #1
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M42-K mount adapter attachment thought.

I know we've kicked this old dog around quite a bit, but I've been thinking about the up coming attachment of my OEM adapter to my SMC Pentax M42 500mm lens. Instead of using blue Locktite, what do you think of taking the tail piece to a watch maker and have him drill three holes in the flange of the adapter and taper them so the screw heads are flush. Then, drill three corresponding holes in the tail piece of the lens and threading them? Then, the adapter would be mechanically attached and relatively easy to detach, should the need arise.


Good idea? Bad idea? So-so idea? Or, stick to the blue Locktite and be done with it?

12-29-2015, 09:57 AM   #2
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Use the adapter as it was designed. The problem with fixing it to a lens is that it does not offer the inherent lock-on mechanics of K lenses. When you take the spring off there will be nothing to stop the lens rotating in mount and falling off - leaving lens falling to the ground and a bare hole on the front of the camera - bad on both points.
12-29-2015, 10:07 AM   #3
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QuoteOriginally posted by Dewman Quote
Good idea? Bad idea? So-so idea? Or, stick to the blue Locktite and be done with it?
I think you are over thinking this. I used a 'fixed' adapter on my S-M-C 400mm for years. I used a k-mount cap to tighten the adapter on the lens as tight as I could get. Which is not all that tight using a plastic cap. It never budged and I had a tough time getting it loose when I sold the lens.

I always mounted the lens onto the tripod first, then attached the camera. Reverse that to put things away. I never trusted this for hand held shooting, although I know people who do. At any rate, the failure point in this combination is the adapter-->camera not the lens-->adapter.

And remember to remove the spring on the adapter when using it like this.
12-29-2015, 10:10 AM   #4
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The M42 and the K mount versions are based on the same lens. It is perhaps too much to hope for, but if you could find a defunct K mount version the mount part could be cannibalized and moved over to your M42 lens.

12-29-2015, 10:18 AM   #5
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I agree with other posters on your thread, there is no need to keep the adapter on the lens as permanent (or semi permanent by tightening it). However, there is one thing that I wish the m42 lens base would have is the indent (hole) that aligns with the camera mount pin so when the lens is fully engaged and aligned properly, it would not wiggle or move at all when you turn the aperture ring.
12-29-2015, 10:20 AM   #6
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To solve the lens locking problem described by Tim60, you could have the jeweler cut a slot in the appropriate position on the lens base so the locking pin on the camera body would engage. It doesn't need to be a deep slot.

Just sayin'.... if you're going to be paying a jeweler for all that, might as well solve all the issues up front. With the adapter screwed to the M42 lens mount, plus 3 countersunk screws, plus a slot in the lens base and the locking pin engaged, the lens won't fall off.
12-29-2015, 10:55 AM   #7
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QuoteOriginally posted by Ole Quote
The M42 and the K mount versions are based on the same lens. It is perhaps too much to hope for, but if you could find a defunct K mount version the mount part could be cannibalized and moved over to your M42 lens.

Man oh man.... wouldn't THAT be sweet! Where on earth would a person go to look for such a part? Eric maybe?
12-29-2015, 10:56 AM   #8
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QuoteOriginally posted by Dewman Quote
Man oh man.... wouldn't THAT be sweet! Where on earth would a person go to look for such a part? Eric maybe?
Ebay?
Wanted section on the forum?

12-29-2015, 11:06 AM   #9
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QuoteOriginally posted by Dewman Quote
Man oh man.... wouldn't THAT be sweet! Where on earth would a person go to look for such a part? Eric maybe?
i searched high and low for one between 2008 and 2010. As nearly as I can tell there are literally none left new anywhere on Earth and used ones never come up. Many were molested to Nikon or other mounts in the 80's; more have been altered as you suggest here. The best solution I have seen is to buy a good K-mount lens, put the mount tube on the better LENS and sell the other lens with the M42 mount. Or buy a K-1000/8 and swap the mount as necessary. But that's a bigger pain than just using the converter.

IIRC, there's a long discussions of the mount tubes on the early pages of the S-M-C Takumar 1000/8 thread in the SLR Lens Discussion Forum started by deadwolfbones.

I had a S-M-C 500/4.5 for a while and commented about my travails. Eric CLA'ed and repaired my lens back then.

Last edited by monochrome; 12-29-2015 at 12:12 PM.
12-29-2015, 11:50 AM   #10
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My comments re the adapter are based on my almost exclusive use of Takumar lenses. I have a genuine adapter, in design configuration in the mount all the time and then use the K3 like an M42 body. Intrigues friends who are surprised it is a digital body.
12-29-2015, 12:05 PM   #11
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i removed the locking tabs on all 3 of my m42 adapters and threw the tabs in the trash. never had a problem with lenses coming loose. sometimes i need to swap lenses from m42 to PK in a hurry and have no time to fiddle with getting that ring off the body.
12-29-2015, 12:21 PM   #12
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Use PURPLE (222) Loctite. It is harder to find, but removes much easier than blue.

Purple Loctite | Loctite Purple - Henkel Adhesives North America
12-30-2015, 01:39 AM   #13
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QuoteOriginally posted by Ole Quote
The M42 and the K mount versions are based on the same lens. It is perhaps too much to hope for, but if you could find a defunct K mount version the mount part could be cannibalized and moved over to your M42 lens.
The problem I see here is, if I understand you correctly, that the lenses are not entirely the same.
The main problem is that the M42 lenses have a smaller diameter, so it is not so easy to add a K-mount to such a lens.

Below is a comparison of the SMC 105/2.8 M42 lens with the same lens in K-mount:

12-30-2015, 01:45 AM   #14
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I think that idea would need machining of the m42 mount.
01-02-2016, 02:05 PM   #15
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You need to look at the 500mm lens. It is much fatter, and I believe that the rear parts could be exchangeable.

QuoteOriginally posted by blende8 Quote
The problem I see here is, if I understand you correctly, that the lenses are not entirely the same.
The main problem is that the M42 lenses have a smaller diameter, so it is not so easy to add a K-mount to such a lens.

Below is a comparison of the SMC 105/2.8 M42 lens with the same lens in K-mount:
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