JIS screwdriver size

[ianwatson]

I'm looking to remove the meter coupling prong from a newly acquired Nikkor. Politely asking a watch repairman has worked well in the past. However, it is time that I did it myself. What size JIS screwdriver would be best?

[pluton]

I just checked on a 50/1.8 Ai and a 28/3.5 K/Ai, and my Vessel brand JIS 00  and JIS 0 both fit in the screws.   The '0' had a bit less free play and therefore is the better choice.
I recently Ai-converted a 16/3.5K and a 28/2.8K using Ai kits, and on both lenses, I left off the prong and filled the holes with gray epoxy glue.

[Roland Vink]

I also tend to remove the meter coupling prong on my AI and AIS lenses - they don't serve a useful purpose on modern cameras and can catch on the inside of the camera bag or scratch the next lens.

On most lenses you can put the screws back in - the chrome screw heads look nicer than empty holds. In some lenses such as the Ai 50/1.8 and 50/1.4, the screws are too long and come in contact with the inner barrel, locking up the aperture ring. I have one lens where the chrome screws were replaced with shorter black-anodised screws. I see this sometimes on ebay listings from Japan so it must be reasonably common there, I don't know where to source those screws from through.

[Akira]

On most lenses you can put the screws back in - the chrome screw heads look nicer than empty holds. In some lenses such as the Ai 50/1.8 and 50/1.4, the screws are too long and come in contact with the inner barrel, locking up the aperture ring. I have one lens where the chrome screws were replaced with shorter black-anodised screws. I see this sometimes on ebay listings from Japan so it must be reasonably common there, I don't know where to source those screws from through.

If you ask Nikon service to remove the prong in Japan, they fill the holes with the short black screws.  So, you could assume that the prong on your lens was "officially" removed in Japan.

[ianwatson]

Keith, thank you for checking.

Roland, I remove the prongs for similar reasons. The lenses also look better without them. Oddly enough, my AI 50/1.4 is quite happy with the screws back in.

[pluton]

Yeah...some prong screws fit back in the holes without extending too far and jamming the aperture ring.  Too-long screws can be cut down. It's easy with big screws, but fiddly with these tiny screws.  I save the prong and the waste screws in a container of salvaged screws from cameras and lenses.

[Steven Paulsen]

Oops, Sorry.

[Steven Paulsen]

I generaly like to leave the prong on the lens. (It helps identify top or bottom before mounting. I still remember well set nikkors to 5.6 before mounting.)

I need to convert a 20mm/F4, but it's too pretty. The consequence of mounting the thing without the Df's prong swung up scares the daylight out of me.

Does anyone have a conversion kit 21, or an old 20mm/f4, junker that I can get an Ai ring?

[Bent Hjarbo]

Not even https://kamerastore.com/products/search-Nikon%20Ai%20kit/ have one

[Roland Vink]

The aperture ring on the 20/4 is relatively thick, it might be thick enough for Marcel Van Engen's Ai conversion - see https://magnimopus.com/services/  He carefully mills out the inside of the aperture ring to produce an Ai ridge, from the outside the lens still looks original. This technique is not suitable for pre-Ai lenses where the wall of the aperture ring is too thin (eg 20/3.5 Auto) but when it works, it is the best AI conversion available. Marcel is active here, send him a PM