Are AI conversions for K lenses are as simply as an aperture ring replcement?  And if so, would the K-AI conversion kit (aperture ring) be the same as the AI ring?

Example:  would the 20mm f/4 K conversion kit have the same aperture ring as the to 20mm f/4 AI?  This kit was listed in the cheaper tier of conversion options based on Roland's info http://www.photosynthesis.co.nz/nikon/aimod.html which suggests labour and parts (and shippping) were reasonable simple.

The background to this is I have a Nikkor 20mm f/4 AI but it's got some problems but have an option on a 20mm f/4 K that is in good condition - I wonder if i can simply swap the aperture rings (from AI onto the K) and have an AI'd K lens.  Milling/filling the K ring is something I dont want to do since I have an AI aperture ring.

The short answer is yes - the AI conversion ring is simply an aperture ring replacement. For lenses like the 20mm 1:4 where the K and AI lens are basically the same, it is reasonable to assume that the AI conversion kit for K lenses was simply the aperture ring from a standard production AI lens.

There is at least one case where the conversion ring is not the same as a standard AI aperture ring. The K 105mm 1:2.5 stops down to f32 and the AI conversion kit retains this aperture range. However, the standard AI 105mm 1:2.5 only stops down to f22 even though it is mostly identical to the K version. There may be others where the AI conversion ring is different from the standard AI ring, but they should still be interchangeable since they need to fit the same lens.

Note that the screws on these lenses are notoriously difficult to budge. You need to use the right tools to avoid damaging your lens.

I think I have an unused AI conversion ring for the 20mm 1:4 lens - let me know if you are interested.

drive by shooting in reverse

Camellia.

Backlit waterfall.

Walk along the river - Z8 & Z400mm f/4.5

Nice birds, well captured.