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Relubing Petri Orikkor 50mm lens
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PostPosted: Thu Mar 23, 2023 5:39 pm    Post subject: Relubing Petri Orikkor 50mm lens Reply with quote

Relubing Kuribayashy C. C. Petri Orikkor 50mm F2 M42
This lens, released on the market in 1959, is very particular and expensive: the optics is composed of seven elements in four groups, including a group of three lenses cemented in the rear unit; the aperture is of the preset type with rear selection ring.

Mine has very stiff focus and aperture setting rings.

On the net there is little information on how to disassemble it: this is the link I used, translated with google translate: https://pakira3.sakura.ne.jp/wp/?p=77220
To loosen rings, screws and pins, use acetone and/or isopropyl alcohol, never force anything, you will break it.
1) Unscrew the chromed ring with the brand counterclockwise.

2) Set the distance to infinity, unscrew the three screws of the focus ring, remove it delicately avoiding to rotate the helicoids and measure the distance between the female aluminum helicoid and the base of the lens with the gauge of the red index of the depth of field. (mine is 1.62mm); mark the measuring point on the female coil. Reassemble the focus ring and set the closest distance, disassemble the focus ring and measure the distance between the female aluminum helicoid and the base of the lens always on the reference of the pink line of the depth of field (mine is 1.80mm); mark the measuring point.

3) Now go to the rear: unscrew the rear light unit, set the aperture to 22, carefully unscrew the two aluminum pins of the black preset ring and remove it. You will see two brass crescents, one of which has a pin that fits into a slot and operates the diaphragm blades. Clean the two crescents with petrol.

4) Now extract the aluminum ring for the aperture values of the diaphragm. (be very careful as there are three small spheres that can jump: carry out the operation inside a cellophane bag). The three spheres are housed in three small holes closed at the back by three blades which act as a spring. Wipe off old grease and recolor numbers if needed.

5) Returning to the front: unscrew the headlight assembly and remove it. A brass ring will appear holding the aperture assembly in place: unscrew the ring with a lens wrench. Take out the aperture assembly and check the cleanliness of the blades (mine are clean).

6) We now have three components: the base of the objective with the depth of field values, the female aluminum helicoid (very thin and delicate) and the male brass helicoid.

7) Set the focus ring to the near-field position (1.75ft) and remove it. Now slowly rotating the male coil counterclockwise with slight tension, you will first hear a slight click (the vertical guide of the male coil comes out of the horizontal pin of the base) and then this will disengage from the female coil: carefully mark the point disengagement on the two elements (if this step is omitted it will be very difficult to reassemble the coils correctly (there are 16 inputs).

Cool Return the female coil to the near-field position marked previously and slowly unscrew the black base ring with the red depth-of-field line with slight tension, counting the turns until it comes off: (mine has 7 turns and about ¾; this is a very important step during reassembly to get the infinity back).

9) Clean all metal elements with petrol or isopropyl alcohol. The optical groups should be cleaned at the end after having reassembled the helicoids and having obtained the infinity.

10) As fats I used Liqui Moly 2003 Mos2 for the preset ring and for the aperture ring and Helimax-Xp for the helicoids.

Paragraph 2: left near field (in yellow 1.8mm distance); to the right infinity (in yellow distance 1.62mm)

Paragraph 3: crescent with pin for preset ring

Paragraph 7: coil disassembly

Paragraph 8: Lens base disassembly

1) After inserting the mini balls in their holes, grease and gently insert the ring of the aluminum diaphragms. Then position the preset ring by colliding the two parts of the green arrow. With a pointed object, mark the position of the two holes in the black base of the mount. Remove the preset ring and insert the two half-moons making the holes collimate between the two parts and screw the two round aluminum pins.

2) Screw the black base into the female coil about 7 ¾ turns with a distance between the two of 1.8mm (close field). Place everything on a horizontal base and with fine clockwise movements insert the male helicoid from the previously marked release point. With fine rotational movements between the male helicoid and the female helicoid, make the vertical guide of the male helicoid reach the horizontal pin of the black base and engage it. Then rotate the female helicoid and the male helicoid will automatically retract reaching infinity.

3) The process is completed by assembling the two optical units and the ring with the brand.

I hope my work can be useful to someone. Obviously this is an experiment and nothing is certain.

PostPosted: Wed May 24, 2023 7:10 pm    Post subject: Very helpful! Reply with quote

Many thanks for your explanation. I have 4 of these lenses (aren't they delightful!) and one is really stiff to focus and I'm sure it simply needs cleaning and re-greasing. Now I have an idea as to how to do this.

PostPosted: Sun May 28, 2023 5:55 am    Post subject: Reply with quote

Thanks for the comment on my post, I hope it will be useful

PostPosted: Tue Oct 24, 2023 4:19 pm    Post subject: Thank you Reply with quote

cesare wrote:
Thanks for the comment on my post, I hope it will be useful

Thanks very much for posting such difficult to find information.

I recently bought an Orikkor 50mm in very dirty condition. Cleaned the optics and it performs very nicely now.

It has a strange problem with the aperture. It seems like the aperture ring is out of position although all the markings seem to line up OK. The blades only move a tiny amount between f2 and f2.8... setting the lens to f4 stops the blades down to approximately where they sound be at f2.8

I need to disassemble the aperture and preset rings. Do you unscrew the two silver 'buttons' to remove that ring?