This Tokina Zoom with a connection for Minolta MD came to me for just EUR 10,-.
Externally in beautiful condition, but with a blocked zoom ring and severe lens clouding.
I wanted to see what I could achieve.
Decorative ring off
After partial dismantling I saw the cause of the blockage.
The two opposing plastic plain bearings in the tube, which hold the focus ring vertically in position, have fallen into pieces and the associated screws have broken off.
An intact - longer - screw below.
After the area has been cleaned of the fragments of the plain bearings, only the remaining screw residue is a reminder of more mobile times.
This is what it looked like in both screw holes.
However, the two diametrical plain bearings for the focal length adjustment are intact.
But they just can't hold the focus ring alone.
Using the Dremel, a metal drill and a small milling knife, I worked my way through the remaining screws.
At first I just drilled a small hole because I wanted to insert a new smaller screw.
Then I discovered two plain bearings with screws in my stash and increased the diameter of the bore.
Freehand and by eye.
And it worked!
The two plain bearings could be screwed into the new holes.
Perfect fit - as if they were original spare parts.
The height was also right.
I was lucky.
All four plain bearings were then lubricated in their guides with Ballistol silicone oil.
After understanding the focusing mechanism, I separated the helicoids.
Previously I marked the infinity and minimum distance positions.
Likewise the point at which the helicoids seperate.
To avoid chemically stressing the plastic bearings, I cleaned the helicoids and the inside of the tube with isopropyl alcohol, the mildest solvent in my box.
Greased with Castrol LMX.
This allows the focus ring to slide smoothly as desired.
The assembly worked, with the markings providing orientation.
Rear and front lens units before …
... and after cleaning with surgical spirit.
Externally in beautiful condition, but with a blocked zoom ring and severe lens clouding.
I wanted to see what I could achieve.
Decorative ring off
After partial dismantling I saw the cause of the blockage.
The two opposing plastic plain bearings in the tube, which hold the focus ring vertically in position, have fallen into pieces and the associated screws have broken off.
An intact - longer - screw below.
After the area has been cleaned of the fragments of the plain bearings, only the remaining screw residue is a reminder of more mobile times.
This is what it looked like in both screw holes.
However, the two diametrical plain bearings for the focal length adjustment are intact.
But they just can't hold the focus ring alone.
Using the Dremel, a metal drill and a small milling knife, I worked my way through the remaining screws.
At first I just drilled a small hole because I wanted to insert a new smaller screw.
Then I discovered two plain bearings with screws in my stash and increased the diameter of the bore.
Freehand and by eye.
And it worked!
The two plain bearings could be screwed into the new holes.
Perfect fit - as if they were original spare parts.
The height was also right.
I was lucky.
All four plain bearings were then lubricated in their guides with Ballistol silicone oil.
After understanding the focusing mechanism, I separated the helicoids.
Previously I marked the infinity and minimum distance positions.
Likewise the point at which the helicoids seperate.
To avoid chemically stressing the plastic bearings, I cleaned the helicoids and the inside of the tube with isopropyl alcohol, the mildest solvent in my box.
Greased with Castrol LMX.
This allows the focus ring to slide smoothly as desired.
The assembly worked, with the markings providing orientation.
Rear and front lens units before …
... and after cleaning with surgical spirit.
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