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04-19-2011, 01:32 PM   #1
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Converting M42 mount to K-mount

Hi.

If I'm understanding the stuff I've read correctly, are these the steps to permanently convert an m42 lens to K-mount?

Buy one of these: (Supposedly it allows focus to infinity)

http://cgi.ebay.com/M42-lens-Pentax-Kx-K7-K20D-adapter-infinite-focusing-/37...#ht_2248wt_877

Then:

1) remove the spring clip on the adapter (I'm not sure where that is, but I can find it)
2) screw it to the lens using a bit of Loctite thread-lock to permanently hold it to the lens
3) mount it to the camera as a K-mount lens
4) mark where the mount locking pin is on the camera
5) remove lens
6) notch lens to match locking pin

I'm looking at using this method with an M42 mirror lens, if that matters.

I would buy a genuine Pentax adapter, but they're getting $45-$65 for them on eBay, which I think is more than a bit nuts.

Thanks,
Bob :-)


Last edited by GibbyTheMole; 04-19-2011 at 02:20 PM.
04-19-2011, 03:26 PM   #2
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The adapter that you are looking at is the wrong type because it will NOT permit infinity focus (it is not flush with the camera body). The description used is erroneous!

You need an adapter that looks like this:

Hin's Tech Corner: Genuine Pentax M42 to K Adapter

Try B&H or ADORAMA or KEH or PENTAX themselves.
04-19-2011, 03:29 PM   #3
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Hi
Don't do that!
You should remove the spring clip if it is not a Pentax adapter but don't glue it on, just use
a rear lens cap to tighten it on to the lens. There is enough friction to hold the lens.
The Pentax adapter is the one that should be used as I found that a lot of lenses
won't even fit onto the camera when using the Made in China ones.The original
is available on the Pentax Web Store for $30.00
What model is that mirrors lens ? Most of them have a T2 mount, if so you can get
a proper PK adapter for it for around $10.00 and save yourself a lot of trouble.
Fotidiox has them.
You are lucky to be in the States, both Pentax and Fotodiox will no longer ship to Canada. !
04-19-2011, 03:30 PM   #4
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Best place to get the genuine adapter is not from ebay but the Pentax store

PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet)


Regarding the alteration from m42 to K mount, not all lens and adapters are suitable for conversion. Your best bet is to get the genuine adapter instead.

Thanks,
Hin


Last edited by hinman; 04-19-2011 at 03:35 PM.
04-19-2011, 03:43 PM   #5
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Original Poster
Thanks for the info, guys. I'll take your advice. Its a 3m-5ca lens and its definitely m42. Wish it were a t-mount. It would be cheaper. Thanks... Bob.
04-19-2011, 03:52 PM   #6
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One more thing... is there a cheaper alternative that would allow focus to infinity and be relatively safe to use with the spring clip removed?
04-19-2011, 04:13 PM - 1 Like   #7
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With just one or two M42 lenses, use the Official Pentax adapter.
With 10 or more M42 lenses (I have ~100) get some cheap clones.
For bellows, macro tubes, portrait lenses, get cheap flanged clones.

On the cheap flangeless (infinity-focus) clones, the screw and clip are easy to see and remove with a jeweler's or eyeglass-repair screwdriver. DO THIS FIRST! Use a rear lens cap as a wrench to tighten the adapter on the lens. Mount the lens. Note where the 6-to-7-o'clock position of the lens is. Get a bit of metal duct-repair tape; remove the adapter; stick the tape on the lens base there; replace (and tighten) the adapter. You are now set to use Catch-In-Focus.

Some of my M39's and M42's have had adapters on them for so long, I've nearly forgotten that they're not native PK-mount lenses. Once I learned to REMOVE THE SCREW AND CLIP! I have had zero problems with the cheap clone adapters.

For lenses where infinity focus isn't important, the cheap safe flanged (no infinity focus) adapters are great. Some cheap teles focus PAST infinity, so such an adapter is just right. For portraits, close-ups, macros, all that stuff, they're just fine.
04-19-2011, 04:34 PM - 1 Like   #8
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Thanks for the great advice, Rico...

So if I'm getting this correctly, these are "flangeless" adapters that do allow infinity focus:

M42 Lens to PK Adapter for Pentax K100D K110D K200D | eBay

M42 Lens to PK Adapter for Pentax K10D K20D Km K7 | eBay

And these are the kind that I don't want:

M42 Lens to PK Adapter for Pentax K100D K110D K200D | eBay

M42 to PK Adapter for Pentax K10D K20D K100D K200D | eBay

The ones that do allow infinite focusing basically have a thinner rim, while the ones that don't allow infinity focus have a wider rim, correct?

You wouldn't happen to have a photo indicating where to stick the metal tape, would you?

Thanks,
Bobbo :-)

04-19-2011, 06:25 PM   #9
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Cool. That Seems simple enough. - Bob.
04-19-2011, 10:46 PM   #10
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QuoteOriginally posted by Wheatfield Quote
I adapted an SMC Tak 17/4 to K mount by removing the spring (genuine Pentax adapter), screwing the adapter to the lens and then using the screw that holds the spring on as a jam screw to hold the adapter to the lens.
I had to notch the lens itself to make the lock pin work, but that was a small thing with a Dremel.
Very helpful information. I have at least 4 M42's and I start to find it very annoying to screw that damn adapter in, each time I change the lens from PK to M42. But for $5-6 / adapter it is reasonable to add one for each lens.
04-20-2011, 07:33 AM   #11
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Hi

Don't worry you can add 1/2 " onto the back of that Russian lens and Still get Infinity !
So the flanged adapter with the locking notch WILL work. I know I have one of
those lenses and made a 1/2" spacer in order to use it on my K100D as the flash
would hit the lens. It still focuses past infinity.
They were designed like that as the factory actually made m42 to T mount adapters, then use a T to whatever. You can still get them from USSR.
Also if you look there are 3 setscrews on the m42 mount, that part comes off and you
will see a groove around the lens part where the set screws seat. Just as the T mounts do.
You can fit a T mount outer adapter onto it. Trouble is the T Mounts have no standards as to
the size of that part, only the threads, so not all of them will fit without mods.
I had to add a spacer shim to the one I used, but it was worth it as it locks on properly and
contacts the camera giving all the Av settings and catch in focus.
04-20-2011, 11:05 AM   #12
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QuoteOriginally posted by bobpur Quote
Hi

Don't worry you can add 1/2 " onto the back of that Russian lens and Still get Infinity !
What lenses you are talking about? None of my Helioses get infinity focus with flanged adapter.
04-20-2011, 11:54 AM   #13
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Hi

Look at the bottom of this page
3M-5CA 8/500 Telephoto lens for Pentax
04-20-2011, 12:30 PM   #14
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QuoteOriginally posted by vanakaru Quote
What lenses you are talking about? None of my Helioses get infinity focus with flanged adapter.
I believe that he is talking about the Mirror Lens ONLY!
04-20-2011, 01:01 PM   #15
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not to really confuse the issue here, but many mirror lenses have the ability to focus past infinity. They do this because of the impact of expansion with temperature.

it may be that the flanged adaptor, which adds 0.8mm between the camera body and lens is thin enough to let it focus. Only you will be able to tell, once you mount the lens to the camera.

Youo could "trial fit" the lens by mounting it on a tripod, and holding the camera firmly against the lens and see if it goes past infinity.

It is worth doing because the flanged adaptor already has a locking hole.

ALso when you do get around to loctiting what ever adaptor to the lens, cover the rear opening first with masking tape. Some loctites release solvents that attack optical surfaces.
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