Leica Tales from the Greasy Side: Komura 105mm F3.5 Teardown.

This thread will be continued as I try to bring this lens into working order.

For now- the teardown, as I could not find this anywhere on the web. This is a fairly uncommon lens in Leica mount. It is similar in construction to the 135mm F3.5 Komura that I relubed- and learned some lessons with. Like: DO NOT SEPARATE THE HELICAL! Too hard to get back together.

The Optical Barrel separates from the focus mount, but this one was very stubborn. A rubber sheet was required to grab the front of the lens and the aperture ring.

31887323677_0c76c1af91_b.jpg
Komura105_barrel_out
by fiftyonepointsix, on Flickr

The chrome trim ring unscrews from the focus ring.

The optical barrel also screws into two sections allowing access to the surfaces on each side of the aperture. The middle group will also come out of the front section, but this was not necessary for this lens.

32953102048_981d317529_b.jpg
Komura105_focus_ring_split2
by fiftyonepointsix, on Flickr

The focus ring is in two sections, I use a silver sharpie to mark positions. Undo the set screw, unscrew the distance ring from the front section.

The front of the focus ring is held in with 3 flat-head screws. Take them out, the focus ring comes off.

Now you can extend the helical for cleaning.

This is about as far as the helical can be extended without separating it.

31887323567_40951c57af_b.jpg
Komura105_Helical_exposed_MAX
by fiftyonepointsix, on Flickr

"Do you feel lucky" in re-assembling? After my experience with the 135/3.5: I am very good at getting these back together. But not THAT lucky. I used acetone to get the old grease off using Q-Tips and paper towels. Held the helical over a pyrex dish, flood cleaned the best possible. Then used white lithium grease, focus is very smooth now.

This lens has a problem: the focus and RF do not agree, and the optics cannot be screwed far enough into the mount to correct the problem. I would have to grind the end of the helical down, and grind down the chrome trim ring. As this is a telephoto lens, I am going to use a shim on the M-Mount adapter instead. The idea is to back the RF cam out just enough for the focus to agree at ~5m. The actual focus of a 105mm lens will not be dramatically affected by a 0.2mm shift, which is about what is required to correct the RF. Will report back later.
 
I paid under $100 for this one, inclusive of shipping. The canon 100/3.5 is smaller and sharper. The Nikkor and Canon 135's are sharper than the Komura, which I picked up for $50. These are decent lenses, "obscure" compared to others. But- I would not pay more for them than any Canon or Nikkor lens.
 
I finally got good agreement between the RF and actual focus. Added a 0.1mm standoff shim between the lens and the M-Mount adapter. This corrected the error between the distance measured by the RF and actual distance to the object at 5m. With the distance and RF in agreement, the lens still had a slight front-focus. I removed the 0.15mm shim from the optics module and screwed it as far as it would go into the focus mount. The agreement is "good enough". I'll be testing it when the weather cooperates. Overall- this lens is lower contrast than expected, soft wide-open, and definitely lacking in calibration to the Leica. This lens was not mis-assembled on some prior repair, all taps for set screws line up perfectly and there are no "extra taps" as would be present if the lens was modified before taking it apart. If this lens was used before- someone calibrated the RF of the camera that it was used on for this lens.

Worth $100 with shipping? The optics are good, now any minor haze is cleaned out. It's an uncommon lens, but not one that would be searched out for it's optical qualities. It is big and heavy compared with the Canon 100/3.5 and Minolta 85/2.8.

Worth the ridiculous prices that sellers on Ebay ask for it? No. The Minolta 85/2.8 can be bought for less, is a much better lens. Mine was spot-on for focus. A clean Canon 100/3.5 would be a better choice, but one with perfect optics is hard to find. The Nikkor 10.5cm F2.5 is faster and sharper, a bit heavier- goes in the $300 range. With that in mind, the Komura is worth the $100 paid, about the same price as a clean Elmar 9cm F4.
 

G-hack

New Member
I joined this forum specifically to check this thread out!

I have the same exact lens, all perfect except a very stiff focus ring. I am tempted to tear down and grease it up, but I have heard the helicoid reassembly is trial and error and difficult.

I'm not a lens repair expert, and wondering if any sites show this helicoid process?

It would break my heart if I look it apart and couldn't piece it back together; it's a nice lens.

Any help would be much appreciated!!!
 
My advice is to NOT separate the helical, but to expose most of it as I have done. Swab the two parts of the helical with alcohol and/or lighter fluid. Clean the exposed section directly, and the inner section using a q-tip from the inside. It works.

The material seems to be a bit softer than other lenses. The process of separating the helical on the 135 Komura seemed to have damaged it- slightly bent the end. It would not go back together. I have separated the helical on hundreds of lenses- "it busted". I had a spare.
 
My advice is to NOT separate the helical, but to expose most of it as I have done. Swab the two parts of the helical with alcohol and/or lighter fluid. Clean the exposed section directly, and the inner section using a q-tip from the inside. It works. Just partially unscrew the helical, as shown here. Work new grease in- which happens as you screw it back in. But not separating...

The material seems to be a bit softer than other lenses. The process of separating the helical on the 135 Komura seemed to have damaged it- slightly bent the end. It would not go back together. I have separated the helical on hundreds of lenses- "it busted". I had a spare.
 

G-hack

New Member
Thanks Brian, that is great advice! I live in Japan, and many of the boards here have nightmares where it took hours, literally, to reassemble this part of the lens. I will pass on your good workaround. Komuras are not so popular in Japan as it is outside, it is a shame as they made good stuff.

Thank you again!
 

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