Nikkor AI Conversion

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Read and follow these sketches at your own risk!

The question of how to convert an old non-AI Nikkor lens to work on a later body comes up often. These sketches show the basics of what it takes to make the lens operate properly, but please be aware that there is some risk of personal injury as well as damage to your lens inherent in this operation. Also, the quality of your results will be a direct function of the equipment you use and the care you take. I have lost neither lens nor fingers in this operation, but I cannot be responsible for your results.

If this makes you nervous, or if you would rather have someone else do a better job for you than you're likely to do yourself, your solution may be right here. (This is not me, I have no association with him, but it looks like he does a good job.)

If you're still feeling cheap and brave, here we go:
This shows how to determine the proper* locations for the ends of the recess you're going to mill in the aperture ring.

* [Please Note: The above method (in my experience) produces a result exactly matching the AI ridge location on Nikon factory AI lenses of f/1.8 and faster maximum aperture. For reasons which are not totally clear to me, Nikon uses a slightly (about 1/3 stop) different AI ridge location on slower lenses. For my purposes, I have found my results to be satisfactory without making this odd distinction, but there must be some reason why Nikon does this. You can find more detail on this by clicking on the "William Sampson AI Modifications" link.]


1. The cutter referred to on the sketches as an "End Mill" is actually a Dremel cutter. It has 10 shallow cutting flutes, and takes a smaller bite and is safer to use than a regular 2- or 4-flute end mill. DO NOT use a conventional end mill for this operation!

2. The best way to hold the part is in a drill press vise, with a set of wood blocks with fitted half-round cutouts to grip the ring without damaging it. If you hold the part in your hands, wear leather work gloves to protect your fingers from the cutter in case you slip.

3. GO SLOWLY! DO NOT try to take more than a few thousandths of depth at a time. Work slowly down from the top, adjusting the cutter downward a few thousandths after you've cut the entire surface at each level as you go.

4. If you don't feel you can perform this operation safely, don't do it. There are people who have the necessary tools and will be happy to do it for you; including one that you can find simply by clicking a link on this page.

In this one, one option for a milling procedure is described. This probably constitutes the MINIMUM setup that can be expected to produce an acceptable result. USE EXTREME CAUTION IN THIS OPERATION TO AVOID DAMAGE OR PERSONAL INJURY! Also note that the aperture ring is removed from the lens for this procedure; the method of removal of the ring varies somewhat from one lens to another.

The dimensions of the aperture rings were not consistent in non-AI lenses, and in some cases the remaining ridge may not be high enough to provide a secure interface for the AI tab. This sketch describes a relatively neat and easy way to provide reinforcement to this area.

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