I was converting some non-AI lenses to AI. The hard part is removing
the aperture ring. Some sample instructions for doing this are posted
on the web:
http://www.zi.ku.dk/personal/lhhansen/photo/repair/aimod/aimod.htm
They fail to mention a crucial detail: Use the right tool for the
cross point screws on these lenses. They say a poor workman blames
his tools, but in this case the right tool really helps.
Japanese cross point screws in lenses are not Phillips. They are JIS
(Japan Industrial Standard) cross point. Phillips drivers have a
slightly angled profile, so they will actually be pushed up and out of
a screw head if you torque them enough, mangling the head. Cross
points are narrower, and straight sided. The difference is dramatic.
A screw will fall off the tip of a Phillips but stay put on a cross
point -- the fit is so good that you can do this and speed up
assembly. But the main thing is they won't mangle the screw heads.
You will have a hard time getting a mangled screw out. Micro tools
has them, but the quality is not quite as good as the Hozan tools I
found here (set D-27 is good): http://www.ikaswebshop.com/jisphilips.html
The second problem is many screws have a loctite goo on them, to keep
them from backing out. Either heat the screw head with a mini torch,
or apply MEK solvent to the screw head, just a drop, and allow it to
penetrate and dissolve the loctite. Put a drop on a tweezer and touch
it to the screw head, it should wick in. Two or three tries may be
needed, but don't force the screw or you will break off the head, then
you're really in trouble. Patience is the key, so don't worry if you
have to set it aside for a few hours to let the solvent work, then
repeat until the screw cooperates.
Nikon has many ways of designing the fastening of the lens mount and
aperture ring, so it's interesting figuring them out. In the end, you
get a lens that is optically wonderful, for about half price.
Before you start, make sure the lens does not have much more value as
is, to a collector. For example, many old non-AI lenses in mint
condition are worth a very high premium to a Nikon collector. Leave
those alone, you can buy three lenses for the price you will get for
one of those. If the lens is a rare one, I would not modify it
either. But if you have common user condition lens you would like to
mount on your modern Nikon, give it a go. Just remember you have to
screw Japanese style.
.
