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01-28-2011, 05:32 PM   #1
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Convert Nikon AIS lens to K mount?

Has anyone done this or know of any shops that will do this? Aperture control isn't a factor for me. Just wondering what is involved.

01-28-2011, 06:41 PM   #2
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Hi
I have converted a 35-105 Macro.
You keep the original Nikon mount as all the mechanism for the aperture is attached to it.
I removed the Nikon flange and sanded the mount completely flat, it then served as the necessary
spacer ( approx. .98mm ) needed to have infinity and hold the aperature control. Remove the 2 protrusions from the Aperture ring so it is flat all around. Remove the silver notched thing from the side.( Keep if to install on a Helios 44-2, will make it latch on your Pentax mount ! )
Then sanded the back of a Pentax Kmount removed from an old lens so it is completly flat.
Using the Nikon mount as a guide drill 3 holes and countersink them. You will reuse the original Nikon
screws.( Align the RED spot on the Pentax base with the Nikon lens aperture spot )
I use the lens like a Preset on AV mode, Focus wide open the just count the clicks and you know what stop
it is on. I have a very sharp and small ( about half the size of my Pentax A ) Lens Cost $5.00 Mint cond !
01-28-2011, 06:47 PM   #3
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Thanks for the highly detailed post! You wouldn't happen to have pictures of each operation as well as the final product would you?
01-28-2011, 07:07 PM   #4
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I have converted some using a slightly different (and simpler) approach.

The bottom of the aperture ring has two protrusions -- I call them the "nub and arc". Leaving the base on the lens, but covering over the rear element with a taped-down plastic bottle cap, I use a Dremel #426 metal cutting disc to remove the "nub and arc", then sand smooth the bottom of the aperture ring. Blow away the dust, and the lens force-fits easily on a Pentax mount.

But that's not a secure mount. What I should do (but haven't yet) is to cut a slot into the lens base, about 1mm wide and deep an 5mm long, in a position where the Pentax locking pin will fit. THEN you have a secure mount, with no disassembly. Depending on the lens, if one of the aperture flags is so long that it touches the Pentax mount, just snip it off with wirecutters.

I have modded a Nikkor 85/2, Paragon 24/2.8, and RMC Tokina 35-135/3.5-4.5, and I'm waiting for a Nikkor 135/3.5 to arrive so I can mod it also. I have also performed simple mods on OM and C/Y lenses, that don't destroy their ability to be use on their native mounts. Minor lens surgery is no big thing. I'm no engineer, just a Dremel-wielding maniac.

01-29-2011, 10:49 AM   #5
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I have converted kiron lenses made for both nikon and minolta by removing the lens mount and using flanged M42 adaptors as the new mount

I have shimmer as necessary to maintain infinity focus and ground off all the external flanges etc that overhang on those mounts but which would interfere on the pentax body

Lenses work in stopped down mode only but that is not really all that bad
01-31-2011, 09:05 AM   #6
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Thanks again for your responses. Have any of you tried the 1.7X AFTC with a converted lens? Does it work well even with the lens stopped down? Also, does the AF still give confirmation in MF mode with your converted lens?
01-31-2011, 11:22 AM   #7
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QuoteOriginally posted by HawaiianOnline Quote
Thanks again for your responses. Have any of you tried the 1.7X AFTC with a converted lens? Does it work well even with the lens stopped down? Also, does the AF still give confirmation in MF mode with your converted lens?
using a flanged adaptor, yes., AF confirmation with Manual Aperture lenses or even M42 lenses requires the data pin( furthest from lens locking pin ) be shorted to the lens mount
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