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DIY AI conversions

Tim Taylor , May 21, 2004; 10:20 a.m.

Does anyone have any experience in modifying non-AI lenses to an AI capability? Some of the more enticing lenses I am after are the pre- AI versions and are at great prices. However, they also seem to not have the AI kits for them available anymore.

How hard is it to modify the lens yourself? What tool(s) are required? What are the measurements for the cut-out and what is the reference point to begin the cut and how long? Do you grind it out and if so, what do you do to protect the lens from 'inhaling' the shavings?

Any web site with this info? I have examined the archives here and searched the Google with no success.

thanks in advance for your help!


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Alan Olander , May 21, 2004; 10:28 a.m.

Here's a link that might help:


Vinny Walsh , May 21, 2004; 11:25 a.m.

John White in Ann Arbor Michigan did mine for $30. I guess you could do it yourself but i wouldn't. www.aiconversions.com He machines a little off and then puts an aperture sticker on the barrel close to the mount, i don't see the need for the sticker though. Hope this helps.

Todd Peach , May 21, 2004; 11:44 a.m.

what do you do to protect the lens from 'inhaling' the shavings?

Simple. You take the aperture ring off before you do anything else. #1 mistake of DIY AI conversions.

Here's a link to Will Sampson's site:

I haven't had any work done by Will, but I have seen his stuff. He's the one I would turn to if I needed conversions.

Jay . , May 21, 2004; 11:51 a.m.

You have to be careful because not every lens can be AI'd well by simply hacking the rear of the aperture ring. Some lenses the aperture ring is too narrow in diameter to reliably engage the AI tab on the camera. One example is the 20/3.5-UD (72mm filter version). This lens requires a bit to be soldered onto the ring where the tab engages. Some AI'd lenses will catch the AI tab at the corner, which is ok on bodies where the tab is metal, but on later bodies where it's plastic it can eventually wear the corner off the tab and then the lens will no longer index.

Jim MacKenzie , May 21, 2004; 11:57 a.m.

The label provides a second aperture scale on the aperture ring. Cameras that use aperture direct readout (ADR) use this to display the selected aperture in the viewfinder. The FM, FE, FA, FE2, FM2, FM2n, and FM3a do this, as well as the F3 and F4 (and I assume F5). It's a very useful touch if you have an ADR body. It makes the AI-converted lens function almost exactly like a real AI lens.

Mike Kovacs , May 21, 2004; 12:47 p.m.

I would second Todd's recommendation for William Sampson. He's a regular at yahoogroups and a class act IMO. You can't really DIY unless you have some experience in machining, probably an end-mill I guess. (I used to have my own light metal fabricator and machinist at work and he was brilliant)

I've seen some real hack jobs on the 2nd hand market. It pays to have a nice AI job if you ever plan to sell.

Gary Watson , May 21, 2004; 02:03 p.m.

DIY conversions are up there with DIY dentistry. You can always just buy a cheap FE body(or any other with a flip-up AI tab)and use stop down metering. Factory jobs aside, AI-conversions I've seen haven't been pretty, nor have they enhanced the value of old Nikkors in otherwise nice condition.

Kelly Flanigan , May 21, 2004; 06:38 p.m.

DIY dentistry; there was a center column main article on this in the WSJ; several years ago!

David H. Hartman , May 22, 2004; 06:03 a.m.

I did one AI modification of a 105/2.5 IC Nikkor. Lacking sophisticated milling tools I used a fine cutting 1/4" square file ground smooth on one side. This allows cutting in only one direction. If you do not know how to properly remove the bayonet it’s a perfect opportunity to torque a head or heads of the screws that secure the bayonet. Doing the modification by hand is slow and tedious. I had two additional 105/2.5(s) available to make comparisons with, an AI and an AIS. This assured that I’d cut ring for the proper fit and angle.

It’s not worth the risk and effort when it can done by someone with the proper tools and considerable experience for just $30.00. I don’t recommend doing your own AI conversions.

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