[Leica] Here's a cheap RF adjustment tool.

[Andrew Moore <moore@rscs.net>]

With all this talk about specialized tools for adjusting the rangefinder
on your M6, I thought I'd post my results.

PLEASE READ THIS THOROUGHLY BEFORE ATTEMPTING TO ADJUST YOUR M6,
ESPECIALLY THE CAUTIONS TOWARDS THE END!

After considering using the wrong tool for the job, I went to my local
Sears store to find the right (ish) tool.  In the tool section I found
a "precision slotted screwdriver".  The one you'll want is clearly
marked on the handle with the model number "Craftsman 41674" and the
size "2.5 x 40".  It costs a whopping $1.99 USD.

Buy two, because you might need one, the other, or both depending upon
the current position of the slot in your M6's rangefinder adjustment
screw.

Note the current position of your M6's rangefinder adjustment screw
(the "infinity" adjustment, which is a screw inside of an eccentric
cam inside the lensmount, near the top).  This will determine where to
put the bend in the screwdriver, relative to the direction of its
slotted blade.  Due to the inaccessability of the adjustment screw,
you might need to modify a couple screwdrivers in order to complete
the adjustment.

Use a couple Vice-Grips or heavy pliers to bend out the blade about 90
degrees (80 or so might suffice).  Do this about half an inch from the
tip.  The shaft is thin and plyable enough that it shouldn't snap.

I also found the "2 x 40" screwdriver size to be useful, though its
blade is a little smaller so it might end up damaging the screw head.

The screw should be adjusted so that with a lens focused at infinity
shows a very distant object in focus through the rangefinder patch.
I focus on a bright star at night, or on a very distant, contrasty
vertical line (telephone pole, tree limb, etc.) during the day.

Cautions:

1. I've heard that there might be another adjustment for close focus,
somehow tied to the infinity focus adjuster, and that you might need
to do make these two adjustments repeatedly, one after the other,
until you zero in on a good pair of settings.  I don't know anything
more about this, and for all I know, I've thrown my M6 out of close
focus.  I'll be doing some tests to find out.

2. archive users: search for followups on this article, because
someone might correct me for something that is horribly wrong.

3. Don't put too much pressure on the screwdriver blade in the
direction of the screw's axis, because if it slips, well, that M6 may
be tough on the OUTSIDE but... (cloth shutter, slice, $, ouch).

4. Don't confuse this infinity focus adjustment with the vertical
rangefinder alignment.  It will NOT fix a rangefinder that isn't
properly locating one image over the other vertically.  I believe that
requires a tool fancier than a $1.99 screwdriver and you should send
it in to Leica to fix.  Unless, of course, you can tell me how to do
it myself....!

5. All of this this applies specifically to the M6 "classic" with
serial numbers 242xxxx and 243xxxx.  It might work for the M6-TTL as
well, but I don't have one, so I can't say for sure, and be aware that
there might be differences in serial numbers that are far apart from
these.

6. Do all this at your own risk.


Questions:

I have noticed that on one particular body this adjustment doesn't
seem to affect my infinity focus setting, even if I throw the
eccentric cam WAY off.  Any ideas?

The cam and the screw move in unison when I adjust the screw via its
slot.  I noticed that the cam itself also has some slots.  Is the
screw really just a "lock down" screw that should move independantly
of the cam?

- --Andrew