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06-09-2014, 07:14 PM   #1
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Scraping "lever" (?) in a K-mount lens

Hi,

Today I tried a for the first time a Vivitar 100mm 3.5 macro with the "A" setting I bought some time ago. First off I disassembled it to get rid of the Ricoh pin; then I screwed it back together and noticed that the lever-like component (I don't know what it is called) that lies recessed in a groove in all of my other lenses is protrudes slightly on this lens. The part I am refering to can be seen in every lens I have and is shown at around 9 o'clock between the two bottom screws on the picture below (which is for illustration purposes only and not my actual lens -- I can of course post a photo of it if anyone would like to see it). It moves when you turn the aperture ring.

http://www.eklecticsystems.com/camera/Images/Sears%2050mm%20f2.0%204.jpg

This protruding part scraped a bit nastily on my K-30's mount (top part) when I mounted it. I took it off carefully and mounted it again on a cheap set of black extension tubes, and the black paint was totally scraped away by the said part. I have therefore three questions:

- Is this a known issue?
- What is the solution? Can I simply disassemble the lens and file off the protruding part of that "lever"? Did I reassemble the lens somewhat incorrectly? (I never mounted the lens with the Ricoh pin on, so I do not know whether the scraping was there before I disassembled it.)
- What does that part of the lens do in the first place and why is it there in the first place? (Please note I am *not* refering to the lever which opens the diaphragm, but rather to the short lever-like component which moves inside a slit in the backside of the lens, as illustrated above, and which can be seen to be firmly attached to the inside of the aperture ring when you take the lens apart).

I am curious to read your comments and thank you for your attention!

06-09-2014, 08:23 PM   #2
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QuoteOriginally posted by Guizo Quote
- Is this a known issue?
I assume you are referring to the inset lever at about 7 o'clock in the linked photo? That is the aperture position coupler and is supposed to be entirely within its groove. It is intended to mate with a coupling lever on the mount of older cameras having the non-crippled K-mount. It serves no purpose on a modern Pentax dSLR.

I have never heard of any "known issue" regarding the aperture position coupler except for when it apparently broken as with your lens. I suspect that at some point somebody removed the mount and did not put it back together properly. You may want to take the mount back off with the intent of seeing how it got the way it is.


Steve
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