Tamron M42 Adapt-A-Matic Mount Actuating Pin Repair

Tamron M42 Adapt a Matic Mount Actuating Pin Assembly Fix

By Wade Spradley

Lens background.

I acquired a few Tamron Adapt-a-Matic mount prime lens for my collection. I was really
interested in the 35mm wideangle which I acquired with a Topcon Adapt-a-Matic mount
for a very reasonable price off the notorious auction site so I could examine it before I
committed myself any further. I determined that the build quality was exceptionable for
the lens for its period. This is one of the few Tamron 35mm wideangle manual focus
prime lenses out there. There is an earlier version that is of a preset design in a T-mount
format. These Adapt-a-Matic lenses were only produced within a 4 year period 1969­1973 according to http://www.adaptall-2.com. During this time many of these designs
were revised. The 35mm wideangle I acquired is one of the later revisions which
involved redesign of aperture ring and focus grip details. No change to the optical design.
The two 28mm wideangles I also added were one each of the original 62mm optical
format and a later revised 58mm optical redesigned of the lens which respectively
involved redesign of aperture ring and focus grip details as well.

I subsequently purchased another Adapt-a-Matic lens for the M42 mount to use on the
35mm wideangle. The two 28mm lens came with their respective M42 Adapt-a-Matic
mounts. The first one is the P-CS model which seems to be a bit more robust with its
internal aperture actuating assembly compared to the later model. The actuating pins on
both models are swaged so they do not fall out and foul the lens being used. The P-CS
model has a larger flat pin base used to activate the arm in contact with the internal lens
aperture throttle. The notch in the M42 mount fits over a screw to align the mount to the
lens used as you carefully emplace the internal mount lever used to make contact with the
lens aperture assembly throttle. Some resistance may be encountered in the attachment.
The M42 mount is in two separate pieces the silver outer ring is screwed on to secure the
M42 mount section to the lens.

The underside of the P-CS Adapt-a-Matic M42 mount. Notice how the lever arm sits on
the flat actuating pin and its size. There is a slight bend to the actuating arm sitting on the
pin, That is normal. Also note the M42 arm with its roller bearing that contacts the
internal lens aperture throttle.