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11-09-2011, 11:13 PM   #1
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I made a 2mm extension "shim" for M42 lenses.

This is just what's needed for getting those short focal length lenses to focus a little closer. The smallest extension tube is too much sometimes. It goes between the lens and adapter. The lens screws on 1.5 turns instead of 3.5. Here are a couple of quick and dirty shots of my EQ, It will not focus to infinity on a Nikon, so it already focuses close. But much closer with the shim. Both are with the Takumar 28 at MFD. I'm sure the difference would be negligible with a telephoto, but really helps with wide angles.





With the shim.




What it looks like.



11-10-2011, 12:09 AM   #2
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Very cool!! This might be something to consider posting in our DIY section later on.

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11-10-2011, 12:39 AM   #3
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Nice. I am looking for 'shims' too. Modifying nikon f to fit pentax k.
11-10-2011, 09:37 AM   #4
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Shims & extensions

Similar topic here #2446

H2

11-10-2011, 11:05 AM   #5
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My lazy way to make a M42 shim is by just wrapping some wire around the thread between the lens body and the wide-flange M42-PK adapter. Use thicker or thinner wire as needed.

QuoteOriginally posted by hoanpham Quote
Nice. I am looking for 'shims' too. Modifying nikon f to fit pentax k.
One method here is to unscrew the Nikon lens base and put 1mm-thick washers on the connecting screws. This pushes the base to pretty precise Pentax registration.
_________________________________________

Some here know the trick for adapting Exakta-mount lenses to PK: Remove and save the index screw from the lens base. Glue an ultra-cheap M39-M42 adapter ring around the lens bayonet. Working against a sheet of 100-grit sandpaper taped to a hard flat ceramic tile, grind away about 0.6mm from a cheap clone narrow-flange M42-PK adapter for the lens to reach infinity focus.

For close work with Exakta-mount lenses, just put an un-ground clone adapter on the lens. For closer shooting, use a safe cheap wide-flange no-infinity-focus M42-PK adapter. That's equivalent to adding about 1.6mm of shim. By just changing adapters, I turn my CZJ Tessar 50/2.8 (12 iris blades) into a close-focus bokeh monster. Deadly sharp, too!
11-10-2011, 11:25 AM   #6
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the ability to make shims is not just for a short extension of M42 lenses, but shims of all diameters are very useful in controlling the regestry distance when swapping lens mounts and using the flanged K-M42 adaptor. I constantly find myself looking for shims in the 1-2mm range.
11-10-2011, 01:53 PM   #7
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QuoteOriginally posted by RioRico Quote
One method here is to unscrew the Nikon lens base and put 1mm-thick washers on the connecting screws. This pushes the base to pretty precise Pentax registration.
that's what i am intent to do, but where can i get those 1.0mm shims? and screws too, since they should be 1.0mm longer?

I have a few PK mount from TCs or tubes, flat type, that can be mounted on any lens, with new holes of course.

Since the ai-s lenses has a metal sticking out at the lens base that prevent a nikon F# mount to pentax body, instead of grinding away the lens barrel, which will reduce the value of the lens next to nothing, i would like to add the 1.0mm shim in between, then the PK mount. The nikkor then can be reversed (except for a few cases where the lens protection aperture pin actually sticking out and hit the mirror box of pentax body)
11-10-2011, 02:22 PM   #8
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Engineers use shims all the time, and I can buy shims in various inside and outside diameters, and obviously thickness' ( in inch and mm ) from all the engineering suppliers around here.
Another good source is heavy vehicle parts dealers. The ball joints on the truck steering is often adjustable for wear by removing shims, so they sell shims for new ball joints, and truck ball joints are big. But car camshaft, crankshaft and many other components use shims to make allowances for manufacturing tolerances.
Here you go, -
http://www.bokers.com/

That's off the top of Google, and obviously as a manufacturer they are going to sell at a minimum quantity, no good when you want one. But the local engineering stockist, the company that sells to the jobbing engineers, will carry or be able to order small amounts. The chances are, if you want one they'll give it to you because the paperwork would cost more.

Make friends with your local engineering suppliers.


Last edited by Lloydy; 11-10-2011 at 02:29 PM.
11-10-2011, 02:29 PM   #9
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Thanks Lloydy,
I am looking at these parts in the local stores myself - but the hard part is to know the part# from a catalog, and the size/dimension that fits the lens mod.
Also, i need to drill hole on these shims. If the metal is too hard, i may have to buy new equipment too ;-)
11-10-2011, 02:37 PM   #10
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If you live or work near an industrial area, the chances are there will be a company there selling engineering consumables. These are the guys you need, not the manufacturers, the guys who know where to source the bits you need.

These days you can buy shims in all manner of materials from rock hard stainless and high carbon steel to plastics and nylon that you could drill with a hand drill.

I've been a hands on maintenance engineer for over 32 years and I know I could walk into any number of stockists tomorrow and get what I wanted in the way of shims, I might have to wait while it's ordered, but I know I could get it.
11-10-2011, 02:56 PM   #11
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Thanks again Lloydy, I have your name in my list ;-)
I don't know many around here doing this kind of work, but i will keep looking for them.

As for the moment, i will try first to dismount the nikkor, check what part i need. I have 2 nikon F mounts that have been modified to fit pentax and may reuse them for other lenses.

The nikkor PC28/3.5 has non ai mount and fits pentax without modification with 8-9mm turn.
I also have the nikkors 400/5.6 ED and 180/2.8 ED that I would like to mod for pentax - if not buying a nikon body.
My dilemma is that those lenses are as new. chopping up will reduce the value that i may have to keep them forever.
11-10-2011, 05:33 PM   #12
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QuoteOriginally posted by hoanpham Quote
Thanks again Lloydy, I have your name in my list ;-)
I don't know many around here doing this kind of work, but i will keep looking for them.

As for the moment, i will try first to dismount the nikkor, check what part i need. I have 2 nikon F mounts that have been modified to fit pentax and may reuse them for other lenses.

The nikkor PC28/3.5 has non ai mount and fits pentax without modification with 8-9mm turn.
I also have the nikkors 400/5.6 ED and 180/2.8 ED that I would like to mod for pentax - if not buying a nikon body.
My dilemma is that those lenses are as new. chopping up will reduce the value that i may have to keep them forever.
it may not necessitate a "chop" nikon has a slightly longer regestry than Pentax. If you get the service manual and can determine if you can adjust infinity focus on the helix by enough to clear the aperture tab remove the old mount and aperture mechanism and add a k mount in its place. You end up with no cutting and a manual aperture billow with a k mount
11-11-2011, 12:11 AM   #13
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Nikkor on pentax has beyond infinity. I was lazy and not try to find a solution for that. The shim is another mod problem. The nikkor ais has metal nubs sticking out at the rear lens barrel (connected to the aperture ring) used to transfer aperture info to the nikon body. These sticking out prevent to mount on pentax body. So either grinding away or 1mm shim to mount on pentax bodies. By grinding, the lens will worth next to nothing, and all ais function is gone.
11-11-2011, 08:16 AM   #14
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QuoteOriginally posted by RioRico Quote
My lazy way to make a M42 shim is by just wrapping some wire around the thread between the lens body and the wide-flange M42-PK adapter. Use thicker or thinner wire as needed.
Neoprene o-rings work too, and even provide a little wiggle room for rotational adjustment.

You can cut 'em out of plastic milk jugs and automotive gasket material as well.

H2
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